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Foods high in magnesium (an example of a nutrient)
Human nutrition deals with the provision of
essential nutrients in food that are necessary to support human
life and
health. Poor nutrition is a chronic problem often linked to poverty,
food security or a poor understanding of nutrition and dietary practices. Malnutrition and its consequences are large contributors to deaths and
disabilities worldwide. Good nutrition helps children grow physically, promotes human biological development and helps in the eradication of poverty.
Overview
The human body contains chemical compounds, such as water, carbohydrates,
amino acids (in
proteins),
fatty acids (in
lipids), and
nucleic acids (
DNA and
RNA). These compounds are composed of
elements
such as carbon, hydrogen, oxygen, nitrogen, phosphorus. Any study done
to determine nutritional status must take into account the state of the
body before and after experiments, as well as the chemical composition
of the whole diet and of all the materials
excreted and eliminated from the body (including
urine
and feces). Comparing food to waste material can help determine the
specific compounds and elements absorbed and metabolized by the body.
The effects of nutrients may only be discernible over an extended
period of time, during which all food and waste must be analyzed. The
number of
variables involved in such
experiments
is high, making nutritional studies time-consuming and expensive, which
explains why the science of human nutrition is still slowly evolving.
Nutrients
The seven major classes of nutrients are
carbohydrates,
fats,
fiber,
minerals,
proteins,
vitamins, and
water. These nutrient classes are categorized as either
macronutrients or
micronutrients (needed in small quantities). The macronutrients are carbohydrates, fats, fiber, proteins, and water. The micronutrients are minerals and vitamins.
The macronutrients (excluding fiber and water) provide structural
material (amino acids from which proteins are built, and lipids from
which cell membranes and some signaling molecules are built), and
energy. Some of the structural material can also be used to generate energy internally, and in either case it is measured in
Joules or
kilocalories
(often called "Calories" and written with a capital 'C' to distinguish
them from little 'c' calories). Carbohydrates and proteins provide 17 kJ
approximately (4 kcal) of energy per gram, while fats provide 37 kJ
(9 kcal) per gram,
though the net energy from either depends on such factors as absorption
and digestive effort, which vary substantially from instance to
instance.
Vitamins, minerals, fiber, and water do not provide energy, but
are required for other reasons. A third class of dietary material, fiber
(i.e., nondigestible material such as cellulose), seems also to be
required, for both mechanical and biochemical reasons, though the exact
reasons remain unclear. For all age groups, males need to consume higher
amounts of macronutrients than females. In general, intakes increase
with age until the second or third decade of life.
Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simple
monosaccharides (glucose, fructose, galactose) to complex
polysaccharides (starch). Fats are
triglycerides, made of assorted
fatty acid monomers bound to a
glycerol backbone. Some fatty acids, but not all, are
essential
in the diet: they cannot be synthesized in the body. Protein molecules
contain nitrogen atoms in addition to carbon, oxygen, and hydrogen. The fundamental components of protein are nitrogen-containing
amino acids, some of which are
essential
in the sense that humans cannot make them internally. Some of the amino
acids are convertible (with the expenditure of energy) to glucose and
can be used for energy production just as ordinary glucose. By breaking
down existing protein, some glucose can be produced internally; the
remaining amino acids are discarded, primarily as urea in urine. This
occurs naturally when
atrophy takes place, or during periods of starvation.
Carbohydrates
Grain products: rich sources of complex and simple carbohydrates
Carbohydrates may be classified as
monosaccharides,
disaccharides or
polysaccharides
depending on the number of monomer (sugar) units they contain. They are
a diverse group of substances, with a range of chemical, physical and
physiological properties. They make up a large part of foods such as
rice,
noodles,
bread, and other
grain-based products, but they are not an essential nutrient, meaning a human does not need to eat carbohydrates.
Monosaccharides contain one sugar unit, disaccharides two, and polysaccharides three or more. Monosaccharides include
glucose,
fructose and
galactose. Disaccharides include
sucrose,
lactose, and
maltose; purified
sucrose, for instance, is used as table sugar. Polysaccharides, which include
starch and
glycogen,
are often referred to as 'complex' carbohydrates because they are
typically long multiple-branched chains of sugar units. The difference
is that complex carbohydrates take longer to digest and absorb since
their sugar units must be separated from the chain before absorption.
The spike in
blood glucose
levels after ingestion of simple sugars is thought to be related to
some of the heart and vascular diseases, which have become more common
in recent times. Simple sugars form a greater part of modern diets than
in the past, perhaps leading to more cardiovascular disease. The degree
of causation is still not clear.
Simple carbohydrates are absorbed quickly, and therefore raise
blood-sugar levels more rapidly than other nutrients. However, the most
important plant carbohydrate nutrient, starch, varies in its absorption.
Gelatinized starch (starch heated for a few minutes in the presence of
water) is far more digestible than plain starch, and starch which has
been divided into fine particles is also more absorbable during
digestion. The increased effort and decreased availability reduces the
available energy from starchy foods substantially and can be seen
experimentally in rats and anecdotally in humans. Additionally, up to a
third of dietary starch may be unavailable due to mechanical or chemical
difficulty.
Fat
A molecule of dietary fat typically consists of several
fatty acids (containing long chains of carbon and hydrogen atoms), bonded to a
glycerol. They are typically found as
triglycerides (three fatty acids attached to one glycerol backbone). Fats may be classified as
saturated or
unsaturated depending on the chemical structure of the fatty acids involved.
Saturated fats have all of the carbon atoms in their fatty acid chains
bonded to hydrogen atoms, whereas unsaturated fats have some of these
carbon atoms
double-bonded,
so their molecules have relatively fewer hydrogen atoms than a
saturated fatty acid of the same length. Unsaturated fats may be further
classified as monounsaturated (one double-bond) or polyunsaturated
(many double-bonds). Furthermore, depending on the location of the
double-bond in the fatty acid chain, unsaturated fatty acids are
classified as
omega-3 or
omega-6 fatty acids.
Trans fats are a type of unsaturated fat with
trans-isomer
bonds; these are rare in nature and in foods from natural sources; they
are typically created in an industrial process called (partial)
hydrogenation.
Many studies have shown that consumption of unsaturated fats,
particularly monounsaturated fats, is associated with better health in
humans. Saturated fats, typically from animal sources, are next in order
of preference, while trans fats are associated with a variety of
disease and should be avoided. Saturated and some trans fats are
typically solid at room temperature (such as
butter or
lard), while unsaturated fats are typically liquids (such as
olive oil or
flaxseed oil). Trans fats are very rare in nature, but have properties useful in the
food processing industry, such as rancidity resistance.
Most fatty acids are not essential, meaning the body can produce
them as needed, generally from other fatty acids and always by expending
energy to do so. However, in humans, at least two fatty acids are
essential and must be included in the diet. An appropriate balance of essential fatty acids –
omega-3 and
omega-6
fatty acids – seems also important for health, though definitive
experimental demonstration has been elusive. Both of these "omega"
long-chain
polyunsaturated fatty acids are
substrates for a class of
eicosanoids known as
prostaglandins, which have roles throughout the human body. They are
hormones, in some respects. The omega-3
eicosapentaenoic acid (EPA), which can be made in the human body from the omega-3 essential fatty acid
alpha-linolenic acid (LNA), or taken in through marine food sources, serves as a building block for series 3 prostaglandins (e.g. weakly
inflammatory
PGE3). The omega-6 dihomo-gamma-linolenic acid (DGLA) serves as a
building block for series 1 prostaglandins (e.g. anti-inflammatory
PGE1), whereas arachidonic acid (AA) serves as a building block for
series 2 prostaglandins (e.g., pro-inflammatory PGE 2). Both DGLA and AA
can be made from the omega-6
linoleic acid
(LA) in the human body, or can be taken in directly through food. An
appropriately balanced intake of omega-3 and omega-6 partly determines
the relative production of different prostaglandins: one reason a
balance between omega-3 and omega-6 is believed important for
cardiovascular health. In industrialized societies, people typically
consume large amounts of processed vegetable oils, which have reduced
amounts of the essential fatty acids along with too much of omega-6
fatty acids relative to omega-3 fatty acids.
Fiber
Dietary fiber is a
carbohydrate,
specifically a polysaccharide, which is incompletely absorbed in humans
and in some animals. Like all carbohydrates, when it is metabolized, it
can produce four Calories (kilocalories) of energy per gram, but in
most circumstances, it accounts for less than that because of its
limited absorption and digestibility. The two subcategories are
insoluble and soluble fiber. Insoluble dietary fiber consists mainly of
cellulose,
a large carbohydrate polymer that is indigestible by humans, because
humans do not have the required enzymes to break it down, and the human
digestive system does not harbor enough of the types of microbes that
can do so. Soluble dietary fiber comprises a variety of
oligosaccharides,
waxes,
esters,
resistant starches, and other carbohydrates that dissolve or gelatinize
in water. Many of these soluble fibers can be fermented or partially
fermented by microbes in the human digestive system to produce
short-chain fatty acids which are absorbed and therefore introduce some
caloric content.
Whole grains, beans and other
legumes, fruits (especially
plums,
prunes, and
figs),
and vegetables are good sources of dietary fiber. Fiber is important to
digestive health and is thought to reduce the risk of colon cancer. For mechanical reasons, fiber can help in alleviating both
constipation and
diarrhea. Fiber provides bulk to the intestinal contents, and insoluble fiber especially stimulates
peristalsis
– the rhythmic muscular contractions of the intestines which move
digesta along the digestive tract. Some soluble fibers produce a
solution of high
viscosity;
this is essentially a gel, which slows the movement of food through the
intestines. Additionally, fiber, perhaps especially that from whole
grains, may help lessen insulin spikes and reduce the risk of type 2
diabetes.
Protein
Proteins are the basis of many animal body structures (e.g. muscles, skin, and hair) and form the
enzymes which catalyse chemical reactions throughout the body. Each protein molecule is composed of
amino acids
which contain nitrogen and sometimes sulphur (these components are
responsible for the distinctive smell of burning protein, such as the
keratin in hair). The body requires amino acids to produce new proteins
(protein retention) and to replace damaged proteins (maintenance).
Amino acids are soluble in the digestive juices within the small
intestine, where they are absorbed into the blood. Once absorbed, they
cannot be stored in the body, so they are either metabolized as required
or excreted in the urine.
Proteins consist of amino acids in different proportions. The
most important aspect and defining characteristic of protein from a
nutritional standpoint is its
amino acid composition.
Amino acids which an animal cannot synthesize on its own from smaller
molecules are deemed essential. The synthesis of some amino acids can be
limited under special pathophysiological conditions, such as
prematurity in the infant or individuals in severe catabolic distress,
and those are called conditionally essential.
A
vegetarian diet can adequately supply protein, support pregnancy, childhood and athletic endeavors, and lower the risk of
cardiovascular disease and
cancer.
Minerals
Dietary minerals are the
chemical elements required by living organisms, other than the four elements
carbon,
hydrogen,
nitrogen, and
oxygen that are present in nearly all
organic molecules.
The term "mineral" is archaic, since the intent is to describe simply
the less common elements in the diet. Some are heavier than the four
just mentioned – including several
metals,
which often occur as ions in the body. Some dietitians recommend that
these be supplied from foods in which they occur naturally, or at least
as complex compounds, or sometimes even from natural inorganic sources
(such as
calcium carbonate from ground
oyster
shells). Some are absorbed much more readily in the ionic forms found
in such sources. On the other hand, minerals are often artificially
added to the diet as supplements; the most well-known is likely iodine
in
iodized salt which prevents
goiter.
Essential dietary minerals
These include the following:
- Chlorine as chloride ions; very common electrolyte; see sodium, below.
- Magnesium, required for processing ATP
and related reactions (builds bone, causes strong peristalsis,
increases flexibility, increases alkalinity). Approximately 50% is in
bone, the remaining 50% is almost all inside body cells, with only about
1% located in extracellular fluid. Food sources include oats,
buckwheat, tofu, nuts, caviar, green leafy vegetables, legumes, and
chocolate.
- Phosphorus, required component of bones; essential for energy processing.
Approximately 80% is found in inorganic portion of bones and teeth.
Phosphorus is a component of every cell, as well as important
metabolites, including DNA, RNA, ATP, and phospholipids. Also important
in pH regulation. Food sources include cheese, egg yolk, milk, meat,
fish, poultry, whole-grain cereals, and many others.
- Potassium,
a very common electrolyte (heart and nerve health). With sodium,
potassium is involved in maintaining normal water balance, osmotic
equilibrium, and acid-base balance. In addition to calcium, it is
important in the regulation of neuromuscular activity. Food sources
include bananas, avocados, vegetables, potatoes, legumes, fish, and
mushrooms.
- Sodium,
a very common electrolyte; not generally found in dietary supplements,
despite being needed in large quantities, because the ion is very common
in food: typically as sodium chloride, or common salt.
Trace minerals
Many elements are required in smaller amounts (microgram quantities), usually because they play a
catalytic role in
enzymes. Some trace mineral elements (RDA < 200 mg/day) are, in alphabetical order:
- Cobalt as a component of the vitamin B12 family of coenzymes
- Copper required component of many redox enzymes, including cytochrome c oxidase
- Chromium required for sugar metabolism
- Iodine required not only for the biosynthesis of thyroxin, but probably, for other important organs as breast, stomach, salivary glands, thymus etc. (see Iodine deficiency);
for this reason iodine is needed in larger quantities than others in
this list, and sometimes classified with the macrominerals; It can be found in iodized salt
- Iron required for many enzymes, and for hemoglobin and some other proteins
- Manganese (processing of oxygen)
- Molybdenum required for xanthine oxidase and related oxidases
- Selenium required for peroxidase (antioxidant proteins)
- Zinc required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, carbonic anhydrase
Vitamins
As with the minerals discussed above, some vitamins are recognized as
essential nutrients, necessary in the diet for good health. (
Vitamin D is the exception: it can alternatively be synthesized in the skin, in the presence of
UVB radiation.) Certain vitamin-like compounds that are recommended in the diet, such as
carnitine,
are thought useful for survival and health, but these are not
"essential" dietary nutrients because the human body has some capacity
to produce them from other compounds. Moreover, thousands of different
phytochemicals have recently been discovered in food (particularly in fresh vegetables), which may have desirable properties including
antioxidant
activity (see below); experimental demonstration has been suggestive
but inconclusive. Other essential nutrients not classed as vitamins
include
essential amino acids (see
above),
essential fatty acids (see
above), and the minerals discussed in the preceding section.
Vitamin deficiencies may result in disease conditions:
goiter,
scurvy,
osteoporosis, impaired
immune system, disorders of cell
metabolism, certain forms of cancer, symptoms of premature
aging, and poor
psychological health (including
eating disorders), among many others.
Malnutrition
Malnutrition refers to insufficient, excessive, or imbalanced
consumption of nutrients. In developed countries, the diseases of
malnutrition are most often associated with nutritional imbalances or
excessive consumption.
Although there are more people in the world who are malnourished due to
excessive consumption, according to the United Nations
World Health Organization,
the greatest challenge in developing nations today is not starvation,
but insufficient nutrition – the lack of nutrients necessary for the
growth and maintenance of vital functions. The causes of malnutrition
are directly linked to inadequate macronutrient consumption and disease,
and are indirectly linked to factors like “household food security,
maternal and child care, health services, and the environment.”
Illnesses
| Nutrients∗
|
Deficiency
|
Excess
|
| Food Energy
|
starvation, marasmus
|
obesity, diabetes mellitus, cardiovascular disease
|
| Simple carbohydrates
|
None.
|
diabetes mellitus, obesity
|
| Complex carbohydrates
|
none
|
obesity
|
| Saturated fat
|
low sex hormone levels
|
cardiovascular disease
|
| Trans fat
|
none
|
cardiovascular disease
|
| Unsaturated fat
|
none
|
obesity
|
| Fat
|
malabsorption of fat-soluble vitamins, rabbit starvation (if protein intake is high), during development: stunted brain development and reduced brain weight.
|
cardiovascular disease
|
| Omega-3 fats
|
cardiovascular disease
|
bleeding, hemorrhages
|
| Omega-6 fats
|
none
|
cardiovascular disease, cancer
|
| Cholesterol
|
during development: deficiencies in myelinization of the brain.
|
cardiovascular disease
|
| Protein
|
kwashiorkor
|
| Sodium
|
hyponatremia
|
hypernatremia, hypertension
|
| Iron
|
anemia
|
cirrhosis, cardiovascular disease
|
| Iodine
|
goiter, hypothyroidism
|
Iodine toxicity (goiter, hypothyroidism)
|
| Vitamin A
|
xerophthalmia and night blindness, low testosterone levels
|
hypervitaminosis A (cirrhosis, hair loss)
|
| Vitamin B1
|
beriberi
|
|
| Vitamin B2
|
cracking of skin and corneal unclearation
|
|
| Niacin
|
pellagra
|
dyspepsia, cardiac arrhythmias, birth defects
|
| Vitamin B12
|
pernicious anemia
|
|
| Vitamin C
|
scurvy
|
diarrhea causing dehydration
|
| Vitamin D
|
rickets, osteoporosis, balance, immune system, inflammation
|
hypervitaminosis D (dehydration, vomiting, constipation)
|
| Vitamin E
|
nervous disorders
|
hypervitaminosis E (anticoagulant: excessive bleeding)
|
| Vitamin K
|
hemorrhage
|
|
| Calcium
|
osteoporosis, tetany, carpopedal spasm, laryngospasm, cardiac arrhythmias
|
fatigue, depression, confusion, anorexia, nausea, vomiting, constipation, pancreatitis, increased urination
|
| Magnesium
|
hypertension
|
weakness, nausea, vomiting, impaired breathing, and hypotension
|
| Potassium
|
hypokalemia, cardiac arrhythmias
|
hyperkalemia, palpitations
|
Mental agility
Research indicates that improving the awareness of nutritious meal
choices and establishing long-term habits of healthy eating has a
positive effect on a cognitive and spatial memory capacity, potentially
increasing a student's potential to process and retain academic
information.
Some organizations have begun working with teachers,
policymakers, and managed food service contractors to mandate improved
nutritional content and increased nutritional resources in school
cafeterias from primary to university level institutions. Health and
nutrition have been proven to have close links with overall educational
success.
Currently less than 10% of American college students report that they
eat the recommended five servings of fruit and vegetables daily.
Better nutrition has been shown to affect both cognitive and spatial
memory performance; a study showed those with higher blood sugar levels
performed better on certain memory tests.
In another study, those who consumed yogurt performed better on
thinking tasks when compared to those who consumed caffeine free diet
soda or confections. Nutritional deficiencies have been shown to have a negative effect on learning behavior in mice as far back as 1951."Better learning performance is associated with diet induced effects on learning and memory ability".
- The "nutrition-learning nexus" demonstrates the correlation
between diet and learning and has application in a higher education
setting..
- We find that better nourished children perform significantly better
in school, partly because they enter school earlier and thus have more
time to learn but mostly because of greater learning productivity per
year of schooling."
- 91% of college students feel that they are in good health while only
7% eat their recommended daily allowance of fruits and vegetables.
- Nutritional education is an effective and workable model in a higher education setting.
- More "engaged" learning models that encompass nutrition is an idea that is picking up steam at all levels of the learning cycle.
Mental disorders
Nutritional supplement treatment may be appropriate for major
depression,
bipolar disorder,
schizophrenia, and
obsessive compulsive disorder, the four most common mental disorders in developed countries.
It is because Lakhan and Vieira mentioned that the supplements possess
amino acids that may change into neurotransmitters and improve mental
disorders. Supplements that have been studied most for mood elevation
and stabilization include
eicosapentaenoic acid and
docosahexaenoic acid (each of which are an
omega-3 fatty acid contained in
fish oil, but not in
flaxseed oil),
vitamin B12,
folic acid, and
inositol.
Cancer
Cancer has become common in developing countries. According to a study by the
International Agency for Research on Cancer,
"In the developing world, cancers of the liver, stomach and esophagus
were more common, often linked to consumption of carcinogenic preserved
foods, such as smoked or salted food, and parasitic infections that
attack organs." Lung cancer rates are rising rapidly in poorer nations
because of increased use of tobacco. Developed countries "tended to have
cancers linked to affluence or a 'Western lifestyle' – cancers of the
colon, rectum, breast and prostate – that can be caused by obesity, lack
of exercise, diet and age."
A comprehensive worldwide report, "
Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective", compiled by the
World Cancer Research Fund and the
American Institute for Cancer Research, reports that there is a significant relation between lifestyle (including food consumption) and
cancer prevention. The same report recommends eating mostly foods of plant origin and aiming to meet
nutritional needs through diet alone, while limiting consumption of
energy-dense foods,
red meat,
alcoholic drinks and
salt and avoiding
sugary drinks,
processed meat and moldy
cereals (grains) or
pulses (legumes). Protein consumption leads to an increase in
IGF-1, which plays a role in cancer development.
Metabolic syndrome and obesity
Several lines of evidence indicate lifestyle-induced
hyperinsulinemia and reduced insulin function (i.e.
insulin resistance)
as decisive factors in many disease states. For example,
hyperinsulinemia and insulin resistance are strongly linked to chronic
inflammation, which in turn is strongly linked to a variety of adverse
developments such as arterial microinjuries and
clot formation (i.e. heart disease) and exaggerated cell division (i.e. cancer). Hyperinsulinemia and insulin resistance (the so-called
metabolic syndrome) are characterized by a combination of abdominal
obesity, elevated
blood sugar, elevated
blood pressure, elevated blood
triglycerides, and reduced HDL
cholesterol.
Obesity can unfavourably alter hormonal and metabolic status via resistance to the hormone
leptin, and a vicious cycle may occur in which insulin/
leptin
resistance and obesity aggravate one another. The vicious cycle is
putatively fuelled by continuously high insulin/leptin stimulation and
fat storage, as a result of high intake of strongly insulin/leptin
stimulating foods and energy. Both insulin and leptin normally function
as satiety signals to the
hypothalamus
in the brain; however, insulin/leptin resistance may reduce this signal
and therefore allow continued overfeeding despite large body fat
stores.
There is a debate about how and to what extent different dietary
factors – such as intake of processed carbohydrates, total protein, fat,
and carbohydrate intake, intake of saturated and trans fatty acids, and
low intake of vitamins/minerals – contribute to the development of
insulin and leptin resistance. Evidence indicates that diets possibly
protective against metabolic syndrome include low saturated and
trans fat intake and foods rich in
dietary fiber, such as high consumption of fruits and vegetables and moderate intake of low-fat dairy products.
Global nutrition challenges
The challenges facing global nutrition are disease, child malnutrition, obesity, and vitamin deficiency.
Disease
The
most common non-infectious diseases worldwide, that contribute most to
the global mortality rate, are cardiovascular diseases, various cancers,
diabetes, and chronic respiratory problems, all of which are linked to
poor nutrition. Nutrition and diet are closely associated with the
leading causes of death, including cardiovascular disease and cancer.
Obesity and high sodium intake can contribute to ischemic heart disease,
while consumption of fruits and vegetables can decrease the risk of
developing cancer.
Foodborne and infectious diseases can result in malnutrition, and
malnutrition exacerbates infectious disease. Poor nutrition leaves
children and adults more susceptible to contracting life-threatening
diseases such as diarrheal infections and respiratory infections.
According to the WHO, in 2011, 6.9 million children died of infectious
diseases like pneumonia, diarrhea, malaria, and neonatal conditions, of
which at least one third were associated with undernutrition.
Child malnutrition
According to UNICEF, in 2011, 101 million children across the globe
were underweight and one in four children, 165 million, were stunted in
growth. Simultaneously, there are 43 million children under five who are overweight or obese.
Nearly 20 million children under 5 suffer from severe acute
malnutrition, a life-threatening condition requiring urgent treatment. According to estimations at
UNICEF,
hunger will be responsible for 5.6 million deaths of children under the age of five this year. These all represent significant public health emergencies.
This is because proper maternal and child nutrition has immense
consequences for survival, acute and chronic disease incidence, normal
growth, and economic productivity of individuals.
Childhood
malnutrition is common and contributes to the
global burden of disease.
Childhood is a particularly important time to achieve good nutrition
status, because poor nutrition has the capability to lock a child in a
vicious cycle of disease susceptibility and recurring sickness, which
threatens cognitive and social development. Undernutrition and bias in access to food and health services leaves children less likely to attend or perform well in school.
Undernutrition
UNICEF defines undernutrition “as the outcome of insufficient food
intake (hunger) and repeated infectious diseases. Under nutrition
includes being underweight for one’s age, too short for one’s age
(stunted), dangerously thin (wasted), and deficient in vitamins and
minerals (micronutrient malnutrient). Under nutrition causes 53% of deaths of children under five across the world. It has been estimated that undernutrition is the underlying cause for 35% of child deaths.
The Maternal and Child Nutrition Study Group estimate that under
nutrition, “including fetal growth restriction, stunting, wasting,
deficiencies of vitamin A and zinc along with suboptimum breastfeeding-
is a cause of 3.1 million child deaths and infant mortality, or 45% of
all child deaths in 2011”.
When humans are undernourished, they no longer maintain normal
bodily functions, such as growth, resistance to infection, or have
satisfactory performance in school or work.
Major causes of under nutrition in young children include lack of
proper breast feeding for infants and illnesses such as diarrhea,
pneumonia, malaria, and HIV/AIDS. According to UNICEF 146 million children across the globe, that one out of four under the age of five, are underweight. The amount of underweight children has decreased since 1990, from 33 percent to 28 percent between 1990 and 2004. Underweight and stunted children are more susceptible to infection,
more likely to fall behind in school, more likely to become overweight
and develop non-infectious diseases, and ultimately earn less than their
non-stunted coworkers. Therefore, undernutrition can accumulate deficiencies in health which results in less productive individuals and societies
Many children are born with the inherent disadvantage of low
birth weight, often caused by intrauterine growth restriction and poor
maternal nutrition, which results in worse growth, development, and
health throughout the course of their lifetime.
Children born at low birthweight (less than 5.5 pounds or 2.5 kg), are
less likely to be healthy and are more susceptible to disease and early
death.
Those born at low birthweight also are likely to have a depressed
immune system, which can increase their chances of heart disease and
diabetes later on in life.
Because 96% of low birthweight occurs in the developing world, low
birthweight is associated with being born to a mother in poverty with
poor nutritional status that has had to perform demanding labor.
Stunting and other forms of undernutrition reduces a child’s chance of survival and hinders their optimal growth and health.
Stunting has demonstrated association with poor brain development,
which reduces cognitive ability, academic performance, and eventually
earning potential.
Important determinants of stunting include the quality and frequency
of infant and child feeding, infectious disease susceptibility, and the
mother’s nutrition and health status. Undernourished mothers are more likely to birth stunted children, perpetuating a cycle of undernutrition and poverty. Stunted children are more likely to develop obesity and chronic diseases upon reaching adulthood.
Therefore, malnutrition resulting in stunting can further worsen the
obesity epidemic, especially in low and middle income countries. This creates even new economic and social challenges for vulnerable impoverished groups.
Data on global and regional food supply shows that consumption
rose from 2011-2012 in all regions. Diets became more diverse, with a
decrease in consumption of cereals and roots and an increase in fruits,
vegetables, and meat products.
However, this increase masks the discrepancies between nations, where
Africa, in particular, saw a decrease in food consumption over the same
years.
This information is derived from food balance sheets that reflect
national food supplies, however, this does not necessarily reflect the
distribution of micro and macronutrients.
Often inequality in food access leaves distribution which uneven,
resulting in undernourishment for some and obesity for others.
Undernourishment, or hunger, according to the FAO, is dietary intake below the minimum daily energy requirement.
The amount of undernourishment is calculated utilizing the average
amount of food available for consumption, the size of the population,
the relative disparities in access to the food, and the minimum calories
required for each individual. According to FAO, 868 million people (12% of the global population) were undernourished in 2012.
This has decreased across the world since 1990, in all regions except
for Africa, where undernourishment has steadily increased. However, the rates of decrease are not sufficient to meet the first
Millennium Development Goal of halving hunger between 1990 and 2015.
The global financial, economic, and food price crisis in 2008 drove
many people to hunger, especially women and children. The spike in food
prices prevented many people from escaping poverty, because the poor
spend a larger proportion of their income on food and farmers are net
consumers of food.
High food prices cause consumers to have less purchasing power and to
substitute more-nutritious foods with low-cost alternatives.
Adult overweight and obesity
Malnutrition in industrialized nations is primarily due to excess
calories and non-nutritious carbohydrates, which has contributed to the
obesity epidemic affecting both developed and some developing nations.
In 2008, 35% of adults above the age of 20 years were overweight (BMI
25 kg/m), a prevalence that has doubled worldwide between 1980 and 2008. Also 10% of men and 14% of women were obese, with a BMI greater than 30.
Rates of overweight and obesity vary across the globe, with the highest
prevalence in the Americas, followed by European nations, where over
50% of the population is overweight or obese.
Obesity is more prevalent amongst high income and higher middle income groups than lower divisions of income. Women are more likely than men to be obese, where the rate of obesity in women doubled from 8% to 14% between 1980 and 2008.
Being overweight as a child has become an increasingly important
indicator for later development of obesity and non-infectious diseases
such as heart disease.
In several western European nations, the prevalence of overweight and
obese children rose by 10% from 1980 to 1990, a rate that has begun to
accelerate recently.
Vitamin and mineral malnutrition
Vitamins and minerals are essential to the proper functioning and maintenance of the human body.
Globally, particularly in developing nations, deficiencies in Iodine,
Iron, and Zinc among others are said to impair human health when these
minerals are not ingested in an adequate quantity. There are 20 trace
elements and minerals that are essential in small quantities to body
function and overall human health.
Iron deficiency is the most common inadequate nutrient worldwide, affecting approximately 2 billion people. Globally, anemia affects 1.6 billion people, and represents a public health emergency in children under five and mothers.
The World Health Organization estimates that there exists 469 million
women of reproductive age and approximately 600 million preschool and
school-age children worldwide who are anemic.
Anemia, especially iron-deficient anemia, is a critical problem for
cognitive developments in children, and its presence leads to maternal
deaths and poor brain and motor development in children.
The development of anemia affects mothers and children more because
infants and children have higher iron requirements for growth.
Health consequences for iron deficiency in young children include
increased perinatal mortality, delayed mental and physical development,
negative behavioral consequences, reduced auditory and visual function,
and impaired physical performance.
The harm caused by iron deficiency during child development cannot be
reversed and result in reduced academic performance, poor physical work
capacity, and decreased productivity in adulthood.
Mothers are also very susceptible to iron-deficient anemia because
women lose iron during menstruation, and rarely supplement it in their
diet.
Maternal iron deficiency anemia increases the chances of maternal
mortality, contributing to at least 18% of maternal deaths in low and
middle income countries.
Vitamin A
plays an essential role in developing the immune system in children,
therefore, it is considered an essential micronutrient that can greatly
affect health.
However, because of the expense of testing for deficiencies, many
developing nations have not been able to fully detect and address
vitamin A deficiency, leaving vitamin A deficiency considered a silent
hunger.
According to estimates, subclinical vitamin A deficiency, characterized
by low retinol levels, affects 190 million pre-school children and 19
million mothers worldwide.
The WHO estimates that 5.2 million of these children under 5 are
affected by night blindness, which is considered clinical vitamin A
deficiency.
Severe vitamin A deficiency (VAD) for developing children can result in
visual impairments, anemia and weakened immunity, and increase their
risk of morbidity and mortality from infectious disease. This also presents a problem for women, with WHO estimating that 9.8 million women are affected by night blindness.
Clinical vitamin A deficiency is particularly common among pregnant
women, with prevalence rates as high as 9.8% in South-East Asia.
Estimates say that 28.5% of the global population is iodine deficient, representing 1.88 billion individuals.
Although salt iodization programs have reduced the prevalence of iodine
deficiency, this is still a public health concern in 32 nations.
Moderate deficiencies are common in Europe and Africa, and over
consumption is common in the Americas.
Iodine-deficient diets can interfere with adequate thyroid hormone
production, which is responsible for normal growth in the brain and
nervous system. This ultimately leads to poor school performance and
impaired intellectual capabilities.
Infant and young child feeding
Improvement
of breast feeding practices, like early initiation and exclusive breast
feeding for the first two years of life, could save the lives of 1.5
million children annually. Nutrition interventions targeted at infants aged 0–5 months first encourages early initiation of breastfeeding.
Though the relationship between early initiation of breast feeding and
improved health outcomes has not been formally established, a recent
study in
Ghana suggests a causal relationship between early initiation and reduced infection-caused neo-natal deaths.
Also, experts promote exclusive breastfeeding, rather than using
formula, which has shown to promote optimal growth, development, and
health of infants.
Exclusive breastfeeding often indicates nutritional status because
infants that consume breast milk are more likely to receive all adequate
nourishment and nutrients that will aid their developing body and
immune system. This leaves children less likely to contract diarrheal
diseases and respiratory infections.
Besides the quality and frequency of breastfeeding, the
nutritional status of mothers affects infant health. When mothers do not
receive proper nutrition, it threatens the wellness and potential of
their children.
Well-nourished women are less likely to experience risks of birth and
are more likely to deliver children who will develop well physically and
mentally.
Maternal undernutrition increases the chances of low-birth weight,
which can increase the risk of infections and asphyxia in fetuses,
increasing the probability of neonatal deaths.
Growth failure during intrauterine conditions, associated with improper
mother nutrition, can contribute to lifelong health complications. Approximately 13 million children are born with
intrauterine growth restriction annually.
International food insecurity and malnutrition
According to UNICEF, South Asia has the highest levels of underweight
children under five, followed by sub-Saharan Africans nations, with
Industrialized countries and Latin nations having the lowest rates.
United States
In the United States, 2% of children are underweight, with under 1%
stunted and 6% are
wasting.
In the US,
dietitians
are registered (RD) or licensed (LD) with the Commission for Dietetic
Registration and the American Dietetic Association, and are only able to
use the title "dietitian," as described by the business and professions
codes of each respective state, when they have met specific educational
and experiential prerequisites and passed a national registration or
licensure examination, respectively. In California, registered
dietitians must abide by the
"Business and Professions Code of Section 2585-2586.8". Archived from the original on 2010-01-11.Anyone
may call themselves a nutritionist, including unqualified dietitians,
as this term is unregulated. Some states, such as the State of Florida,
have begun to include the title "nutritionist" in state licensure
requirements. Most governments provide guidance on nutrition, and some
also impose
mandatory disclosure/labeling requirements for processed food manufacturers and restaurants to assist consumers in complying with such guidance.
In the US, nutritional standards and recommendations are established jointly by the
US Department of Agriculture and
US Department of Health and Human Services. Dietary and physical activity guidelines from the USDA are presented in the concept of a
plate of food which in 2011 superseded the
MyPyramid food pyramid that had replaced the
Four Food Groups. The Senate committee currently responsible for oversight of the USDA is the
Agriculture, Nutrition and Forestry Committee. Committee hearings are often televised on
C-SPAN. The
U.S. Department of Health and Human Services provides a sample week-long menu which fulfills the nutritional recommendations of the government.
Canada's Food Guide is another governmental recommendation.
Industrialized countries
According to
UNICEF, the
Commonwealth of Independent States has the lowest rates of
stunting and
wasting, at 14 percent and 3 percent. The nations of Estonia, Finland, Iceland, Lithuania and Sweden have the lowest prevalence of low
birthweight children in the world- at 4%. Proper prenatal nutrition is responsible for this small prevalence of low birthweight infants. However, low birthweight rates are increasing, due to the use of
fertility drugs,
resulting in multiple births, women bearing children at an older age,
and the advancement of technology allowing more pre-term infants to
survive. Industrialized nations more often face malnutrition in the form of
over-nutrition from excess calories and non-nutritious carbohydrates,
which has contributed greatly to the public health epidemic of obesity.
Disparities, according to gender, geographic location and
socio-economic position, both within and between countries, represent
the biggest threat to child nutrition in industrialized countries. These
disparities are a direct product of social inequalities and
social inequalities are rising throughout the industrialized world, particularly in Europe.
South Asia
South Asia has the highest percentage and number of underweight children under five in the world, at approximately 78 million children.
Patterns of stunting and wasting are similar, where 44% have not
reached optimal height and 15% are wasted, rates much higher than any
other regions. This region of the world has extremely high rates of child underweight- 46% of its child population under five is underweight. India, Bangladesh, and Pakistan alone account for half the globe’s underweight child population. South Asian nations have made progress towards the
MDGs,
considering the rate has decreased from 53% since 1990, however, a 1.7%
decrease of underweight prevalence per year will not be sufficient to
meet the 2015 goal. Some nations, such as
Afghanistan,
Bangladesh, and
Sri Lanka, on the other hand, have made significant improvements, all decreasing their prevalence by half in ten years. While
India and
Pakistan have made modest improvements,
Nepal has made no significant improvement in underweight child prevalence.
Other forms of undernutrition have continued to persist with high
resistance to improvement, such as the prevalence of stunting and
wasting, which has not changed significantly in the past 10 years.
Causes of this poor nutrition include energy-insufficient diets, poor
sanitation conditions, and the gender disparities in educational and
social status.
Girls and women face discrimination especially in nutrition status,
where South Asia is the only region in the world where girls are more
likely to be underweight than boys.
In South Asia, 60% of children in the lowest quintile are underweight,
compared to only 26% in the highest quintile, and the rate of reduction
of underweight is slower amongst the poorest.
Eastern/South Africa
The Eastern and Southern African nations have shown no improvement since 1990 in the rate of underweight children under five. They have also made no progress in halving hunger by 2015, the most prevalent
Millennium Development Goal.
This is due primarily to the prevalence of famine, declined
agricultural productivity, food emergencies, drought, conflict, and
increased poverty. This, along with
HIV/
AIDS, has inhibited the nutrition development of nations such as
Lesotho,
Malawi,
Mozambique,
Swaziland,
Zambia and
Zimbabwe.
Botswana
has made remarkable achievements in reducing underweight prevalence,
dropping 4% in 4 years, despite its place as the second leader in HIV
prevalence amongst adults in the globe.
South Africa,
the wealthiest nation in this region, has the second lowest proportion
of underweight children at 12%, but has been steadily increasing in
underweight prevalence since 1995. Almost half of
Ethiopian children are underweight, and along with
Nigeria, they account for almost one-third of the underweight under five in all of
Sub-Saharan Africa.
West/Central Africa
West/
Central Africa has the highest rate of children under five underweight in the world. Of the countries in this region, the Congo has the lowest rate at 14%, while the nations of
Democratic Republic of the Congo,
Ghana,
Guinea,
Mali,
Nigeria,
Senegal and
Togo are improving slowly. In
Gambia,
rates decreased from 26% to 17% in four years, and their coverage of
vitamin A supplementation reaches 91% of vulnerable populations. This region has the next highest proportion of wasted children, with 10% of the population under five not at optimal weight.
Little improvement has been made between the years of 1990 and 2004 in
reducing the rates of underweight children under five, whose rate stayed
approximately the same.
Sierra Leone
has the highest child under five mortality rate in the world, due
predominantly to its extreme infant mortality rate, at 238 deaths per
1000 live births.
Other contributing factors include the high rate of low birthweight
children (23%) and low levels of exclusive breast feeding (4%). Anemia is prevalent in these nations, with unacceptable rates of iron deficient anemia. The nutritional status of children is further indicated by its high rate of child wasting - 10%. Wasting is a significant problem in Sahelian countries –
Burkina Faso,
Chad,
Mali,
Mauritania and
Niger – where rates fall between 11% and 19% of under fives, affecting more than 1 million children.
Middle East/North Africa
Six countries in the
Middle East and
North Africa region are on target to meet goals for reducing underweight children by 2015, and 12 countries have prevalence rates below 10%.
However, the nutrition of children in the region as a whole has
degraded for the past ten years due to the increasing portion of
underweight children in three populous nations –
Iraq,
Sudan, and
Yemen. Forty six percent of all children in
Yemen are underweight, a percentage that has worsened by 4% since 1990. In Yemen, 53% of children under five are stunted and 32% are born at low birth weight. Sudan has an underweight prevalence of 41%, and the highest proportion of wasted children in the region at 16%. One percent of households in Sudan consume iodized salt. Iraq has also seen an increase in child underweight since 1990.
Djibouti,
Jordan, the
Occupied Palestinian Territory (OPT),
Oman, the
Syrian Arab Republic and
Tunisia are all projected to meet minimum nutrition goals, with OPT, Syrian AR, and Tunisia the fastest improving regions. This region demonstrates that undernutrition does not always improve with economic prosperity, where the
United Arab Emirates, for example, despite being a wealthy nation, has similar child death rates due to malnutrition to those seen in
Yemen.
East Asia/Pacific
The
East Asia/Pacific region has reached its goals on nutrition, in part due to the improvements contributed by
China, the region’s most populous country. China has reduced its underweight prevalence from 19 percent to 8 percent between 1990 and 2002.
China played the largest role in the world in decreasing the rate of
children under five underweight between 1990 and 2004, halving the
prevalence.
This reduction of underweight prevalence has aided in the lowering of
the under 5 mortality rate from 49 to 31 of 1000. They also have a low
birthweight rate at 4%, a rate comparable to industrialized countries,
and over 90% of households receive adequate iodized salts.
However, large disparities exist between children in rural and urban
areas, where 5 provinces in China leave 1.5 million children iodine
deficient and susceptible to diseases.
Singapore,
Vietnam,
Malaysia, and
Indonesia are all projected to reach nutrition MDGs.
Singapore has the lowest under five mortality rate of any nation, besides
Iceland, in the world, at 3%.
Cambodia
has the highest rate of child mortality in the region (141 per 1,000
live births), while still its proportion of underweight children
increased by 5 percent to 45% in 2000. Further nutrient indicators show
that only 12 per cent of Cambodian babies are exclusively breastfed and
only 14 per cent of households consume
iodized salt.
Latin America/Caribbean
This region has undergone the fastest progress in decreasing poor nutrition status of children in the world. The
Latin American
region has reduced underweight children prevalence by 3.8% every year
between 1990 and 2004, with a current rate of 7% underweight. They also have the lowest rate of child mortality in the developing world, with only 31 per 1000 deaths, and the highest
iodine consumption.
Cuba has seen improvement from 9 to 4 percent underweight under 5 between 1996 and 2004. The prevalence has also decreased in the
Dominican Republic,
Jamaica,
Peru, and
Chile. Chile has a rate of underweight under 5, at merely 1%. The most populous nations,
Brazil and
Mexico, mostly have relatively low rates of underweight under 5, with only 6% and 8%.
Guatemala has the highest percentage of underweight and stunted children in the region, with rates above 45%.
There are disparities amongst different populations in this region. For
example, children in rural areas have twice the prevalence of
underweight at 13%, compared to urban areas at 5%.
Nutrition access disparities
Occurring throughout the world, lack of proper nutrition is both a consequence and cause of poverty.
Impoverished individuals are less likely to have access to nutritious
food and to escape from poverty than those who have healthy diets. Disparities in
socioeconomic
status, both between and within nations, provide the largest threat to
child nutrition in industrialized nations, where social inequality is on
the rise. According to UNICEF, children living in the poorest households are twice as likely to be
underweight as those in the richest. Those in the lowest wealth
quintile and whose mothers have the least education demonstrate the highest rates of child mortality and
stunting.
Throughout the developing world, socioeconomic inequality in childhood
malnutrition is more severe than in upper income brackets, regardless of
the general rate of malnutrition. Concurrently, the greatest increase in
childhood obesity has been seen in the lower middle income bracket.
According to UNICEF, children in rural locations are more than
twice as likely to be underweight as compared to children under five in
urban areas.
In Latin American/Caribbean nations, “Children living in rural areas in
Bolivia, Honduras, Mexico and Nicaragua are more than twice as likely
to be underweight as children living in urban areas. That likelihood
doubles to four times in Peru.”
In the United States, the incidence of low birthweight is on the rise among all populations, but particularly among
minorities.
According to UNICEF, boys and girls have almost identical rates as underweight children under age 5 across the world, except in
South Asia.
Nutrition policy
Nutrition interventions
Nutrition
directly influences progress towards meeting the Millennium Goals of
eradicating hunger and poverty through health and education.
Therefore, nutrition interventions take a multi-faceted approach to
improve the nutrition status of various populations. Policy and
programming must target both individual behavioral changes and policy
approaches to public health. While most nutrition interventions focus on
delivery through the health-sector, non-health sector interventions
targeting agriculture, water and sanitation, and education are important
as well.
Global nutrition micro-nutrient deficiencies often receive large-scale
solution approaches by deploying large governmental and non-governmental
organizations. For example, in 1990, iodine deficiency was particularly
prevalent, with one in five households, or 1.7 billion people, not
consuming adequate iodine, leaving them at risk to develop associated
diseases.
Therefore, a global campaign to iodize salt to eliminate iodine
deficiency successfully boosted the rate to 69% of households in the
world consuming adequate amounts of iodine.
Emergencies and crises often exacerbate undernutrition, due to
the aftermath of crises that include food insecurity, poor health
resources, unhealthy environments, and poor healthcare practices. Therefore, the repercussions of natural disasters and other emergencies
can exponentially increase the rates of macro and micronutrient
deficiencies in populations.
Disaster relief interventions often take a multi-faceted public health
approach. UNICEF’s programming targeting nutrition services amongst
disaster settings include nutrition assessments, measles immunization,
vitamin A supplementation, provision of fortified foods and
micronutrient supplements, support for breastfeeding and complementary
feeding for infants and young children, and therapeutic and
supplementary feeding.
For example, during Nigeria’s food crisis of 2005, 300,000 children
received therapeutic nutrition feeding programs through the
collaboration of UNICEF, the Niger government, the World Food Programme,
and 24 NGOs utilizing community and facility based feeding schemes.
Interventions aimed at pregnant women, infants, and children take
a behavioral and program-based approach. Behavioral intervention
objectives include promoting proper breast-feeding, the immediate
initiation of breastfeeding, and its continuation through 2 years and
beyond.
UNICEF recognizes that to promote these behaviors, healthful
environments must be established conducive to promoting these behaviors,
like healthy hospital environments, skilled health workers, support in
the public and workplace, and removing negative influences.
Finally, other interventions include provisions of adequate micro and
macro nutrients such as iron, anemia, and vitamin A supplements and
vitamin-fortified foods and ready-to-use products.
Programs addressing micro-nutrient deficiencies, such as those aimed at
anemia, have attempted to provide iron supplementation to pregnant and
lactating women. However, because supplementation often occurs too late,
these programs have had little effect.
Interventions such as women’s nutrition, early and exclusive
breastfeeding, appropriate complementary food and micronutrient
supplementation have proven to reduce stunting and other manifestations
of undernutrition.
A Cochrane review of community-based maternal health packages showed
that this community-based approach improved the initiation of
breastfeeding within one hour of birth.
Some programs have had adverse effects. One example is the “Formula for
Oil” relief program in Iraq, which resulted in the replacement of
breastfeeding for formula, which has negatively affected infant
nutrition.
Implementation and delivery platforms
In
April 2010, the World Bank and the IMF released a policy briefing
entitled “Scaling up Nutrition (SUN): A Framework for action” that
represented a partnered effort to address the Lancet’s Series on under
nutrition, and the goals it set out for improving under nutrition.
They emphasized the 1000 days after birth as the prime window for
effective nutrition intervention, encouraging programming that was
cost-effective and showed significant cognitive improvement in
populations, as well as enhanced productivity and economic growth. This document was labeled the SUN framework, and was launched by the
UN General Assembly in 2010 as a road map encouraging the coherence of stakeholders like governments,
academia, UN system organizations and foundations in working towards reducing under nutrition.
The SUN framework has initiated a transformation in global nutrition-
calling for country-based nutrition programs, increasing evidence based
and cost–effective interventions, and “integrating nutrition within
national strategies for
gender equality, agriculture,
food security,
social protection, education, water supply, sanitation, and health care”.
Government often plays a role in implementing nutrition programs
through policy. For instance, several East Asian nations have enacted
legislation to increase iodization of salt to increase household
consumption.
Political commitment in the form of evidence-based effective national
policies and programs, trained skilled community nutrition workers, and
effective communication and advocacy can all work to decrease
malnutrition. Market and industrial production can play a role as well. For example, in the
Philippines, improved production and market availability of iodized salt increased household consumption.
While most nutrition interventions are delivered directly through
governments and health services, other sectors, such as agriculture,
water and sanitation, and education, are vital for nutrition promotion
as well.
Nutrition Education
Nutrition is
taught in schools in many countries. In
England and Wales the
Personal and Social Education
and Food Technology curricula include nutrition, stressing the
importance of a balanced diet and teaching how to read nutrition labels
on packaging. In many schools a Nutrition class will fall within the
Family and Consumer Science or Health departments. In some American
schools, students are required to take a certain number of FCS or Health
related classes. Nutrition is offered at many schools, and if it is
not a class of its own, nutrition is included in other FCS or Health
classes such as: Life Skills, Independent Living, Single Survival,
Freshmen Connection, Health etc. In many Nutrition classes, students
learn about the food groups, the food pyramid, Daily Recommended
Allowances, calories, vitamins, minerals, malnutrition, physical
activity, healthy food choices and how to live a healthy life.
A 1985 US
National Research Council report entitled
Nutrition Education in US Medical Schools concluded that nutrition education in medical schools was inadequate.
Only 20% of the schools surveyed taught nutrition as a separate,
required course. A 2006 survey found that this number had risen to 30%.
Nutrition for special populations
Sports nutrition
Protein
The
protein requirement for each individual differs, as do opinions about
whether and to what extent physically active people require more
protein. The 2005
Recommended Dietary Allowances
(RDA), aimed at the general healthy adult population, provide for an
intake of 0.8 grams of protein per kilogram of body weight.
A review panel stating that "no additional dietary protein is suggested
for healthy adults undertaking resistance or endurance exercise."
Carbohydrates
The
main fuel used by the body during exercise is carbohydrates, which is
stored in muscle as glycogen – a form of sugar. During exercise, muscle
glycogen reserves can be used up, especially when activities last longer
than 90 min.
Because the amount of glycogen stored in the body is limited, it is
important for athletes participating in endurance sports such as
marathons to consume carbohydrates during their events.
Paediatric nutrition
Adequate
nutrition is essential for the growth of children from infancy right
through until adolescence. Some nutrients are specifically required for
growth on top of nutrients required for normal body maintenance, in
particular calcium and iron.
Elderly nutrition
Malnutrition in general is higher among the elderly, but has different aspects in developed and undeveloped countries.
History
Humans have evolved as
omnivorous hunter-gatherers
over the past 250,000 years. The diet of early modern humans varied
significantly depending on location and climate. The diet in the tropics
tended to depend more heavily on plant foods, while the diet at higher
latitudes tended more towards animal products. Analyses of postcranial
and cranial remains of humans and animals from the Neolithic, along with
detailed bone-modification studies, have shown that
cannibalism also occurred among prehistoric humans.
Agriculture developed about 10,000 years ago in multiple locations throughout the world, providing
grains (such as
wheat,
rice and
maize) and
potatoes; and originating staples such as
bread and pasta
dough), and
tortillas.
Farming also provided milk and dairy products, and sharply increased
the availability of meats and the diversity of vegetables. The importance of food purity was recognized when bulk storage led to infestation and contamination risks.
Cooking developed as an often ritualistic activity,
due to efficiency and reliability concerns requiring adherence to strict
recipes and procedures, and in response to demands for food purity and
consistency.
From antiquity to 1900
Around 3000 BC the
Vedic texts made mention of scientific research on nutrition. The Bible's
Book of Daniel recounts first recorded nutritional experiment. During an invasion of Judah, King
Nebuchadnezzar of
Babylon
captured Daniel and his friends. Selected as court servants, they were
to share in the king's fine foods and wine. But they objected,
preferring vegetables (
pulses) and water in accordance with their
Jewish dietary restrictions. The king's chief steward reluctantly agreed to a trial.
Daniel and his friends received their diet for 10 days. On comparison
with the king's men, they appeared healthier, and were allowed to
continue with their diet. Around 475 BC,
Anaxagoras
stated that food is absorbed by the human body and therefore contained
"homeomerics" (generative components), suggesting the existence of
nutrients. Around 400 BC,
Hippocrates said: "Let food be your medicine and medicine be your food."
The 16th-century scientist and artist
Leonardo da Vinci (1452–1519) compared
metabolism to a burning candle. In 1747 Dr.
James Lind, a physician in the British navy, performed the first attested
scientific nutrition experiment, discovering that
lime juice saved sailors who had been at sea for years from
scurvy, a deadly and painful bleeding disorder. The discovery was ignored for forty years, but after about 1850 British sailors became known as "
limeys". (Scientists would not identify the essential
vitamin C within lime juice until the 1930s.)
Around 1770
Antoine Lavoisier, the "Father of Nutrition and Chemistry", discovered the details of metabolism, demonstrating that the
oxidation of food is the source of body heat. In 1790
George Fordyce recognized
calcium as necessary for fowl survival. In the early 19th century, the elements
carbon,
nitrogen,
hydrogen and
oxygen were recognized as the primary components of food, and methods to measure their proportions were developed.
In 1816
François Magendie discovered that dogs fed only
carbohydrates and
fat lost their body
protein and died in a few weeks, but dogs also fed protein survived, identifying protein as an essential dietary component.
[citation needed] In 1840,
Justus Liebig discovered the chemical makeup of carbohydrates (
sugars), fats (
fatty acids) and proteins (
amino acids). In the 1860s
Claude Bernard discovered that body fat can be synthesized from carbohydrate and protein, showing that the energy in blood
glucose can be stored as fat or as
glycogen. In the early 1880s
Kanehiro Takaki observed that Japanese sailors (whose diets consisted almost entirely of white rice) developed
beriberi
(or endemic neuritis, a disease causing heart problems and paralysis),
but British sailors and Japanese naval officers did not. Adding various
types of vegetables and meats to the diets of Japanese sailors prevented
the disease.
In 1896
Eugen Baumann observed
iodine in thyroid glands. In 1897,
Christiaan Eijkman worked with natives of
Java,
who also suffered from beriberi. Eijkman observed that chickens fed the
native diet of white rice developed the symptoms of beriberi, but
remained healthy when fed unprocessed brown rice with the outer bran
intact. Eijkman cured the natives by feeding them brown rice,
demonstrating that food can cure disease. Over two decades later,
nutritionists learned that the outer rice bran contains vitamin B.
From 1900 to the present
In the early 20th century
Carl von Voit and
Max Rubner independently measured
caloric energy expenditure in different species of animals, applying principles of physics in nutrition. In 1906, Wilcock and
Hopkins showed that the amino acid
tryptophan was necessary for the survival of rats. He
fed them a special mixture of food containing all the nutrients he
believed were essential for survival, but the rats died. A second group
of rats to which he also fed an amount of milk containing
vitamins.
Gowland Hopkins recognized "accessory food factors" other than calories, protein and
minerals, as
organic materials essential to health but which the body cannot synthesize. In 1907
Stephen M. Babcock and
Edwin B. Hart conducted the
single-grain experiment. This experiment ran through 1911.
In 1912
Casimir Funk coined the term
vitamin
to label a vital factor in the diet: from the words "vital" and
"amine," because these unknown substances preventing scurvy, beriberi,
and
pellagra, were thought then to derive from ammonia. The vitamins were studied in the first half of the 20th century. In 1913
Elmer McCollum discovered the first vitamins, fat-soluble
vitamin A and water-soluble
vitamin B (in 1915; later identified as a complex of several water-soluble vitamins) and named
vitamin C as the then-unknown substance preventing scurvy.
Lafayette Mendel (1872-1935) and
Thomas Osborne (1859–1929) also performed pioneering work on vitamins A and B. In 1919 Sir
Edward Mellanby incorrectly identified
rickets as a vitamin A deficiency, because he could cure it in dogs with
cod-liver oil. In 1922 McCollum destroyed the vitamin A in cod liver oil but found it still cured rickets, thus identifying
vitamin D. Also in 1922, H.M. Evans and L.S. Bishop discovered
vitamin E as essential for rat pregnancy, and originally called it "food factor X" until 1925.
In 1925 Hart discovered that
iron absorption requires trace amounts of
copper. In 1927
Adolf Otto Reinhold Windaus synthesized vitamin D, for which he won the
Nobel Prize in Chemistry in 1928. In 1928
Albert Szent-Györgyi isolated
ascorbic acid,
and in 1932 proved that it is vitamin C by preventing scurvy. In 1935
he synthesized it, and in 1937 won a Nobel Prize for his efforts.
Szent-Györgyi concurrently elucidated much of the
citric acid cycle. In the 1930s
William Cumming Rose identified
essential amino acids, necessary protein components which the body cannot synthesize. In 1935
Eric Underwood and
Hedley Marston independently discovered the necessity of
cobalt. In 1936
Eugene Floyd Dubois showed that work and school performance relate to caloric intake. In 1938
Erhard Fernholz discovered the chemical structure of vitamin E. It was synthesised by
Paul Karrer (1889–1971).
From 1940
rationing in the United Kingdom – during and after World War II – took place according to nutritional principles drawn up by
Elsie Widdowson and others. In 1941 the
National Research Council established the first
Recommended Dietary Allowances (RDAs). In 1992 the U.S. Department of Agriculture introduced the
Food Guide Pyramid. In 2002 a
Natural Justice study showed a relation between nutrition and violent behavior. In 2005 a study found that in addition to bad nutrition,
adenovirus may cause obesity.
