Leafy green, allium, and cruciferous vegetables are key components of a healthy diet
A healthy diet is a diet that helps to maintain or improve overall health. A healthy diet provides the body with essential nutrition: fluid, macronutrients, micronutrients, and adequate calories.[1][2]
The requirements for a healthy diet can be met from a variety of plant-based and animal-based foods, although a non-animal source of vitamin B12 is needed for those following a vegan diet.[3] A healthy diet supports energy needs and provides for human nutrition without exposure to toxicity or excessive weight gain from consuming more calories than the body requires. A healthy diet, in addition to exercise, may lower disease risks, such as obesity, heart disease, type 2 diabetes, hypertension and cancer.[1][4]
Various nutrition guides are published by medical and governmental institutions to educate individuals on what they should be eating to promote health. Nutrition facts labels are also mandatory in some countries to allow consumers to choose between foods based on the components relevant to health.[5]
The idea of dietary therapy (using dietary choices to maintain health and improve poor health) is quite old and thus has both modern scientific forms (medical nutrition therapy) and prescientific forms (such as dietary therapy in traditional Chinese medicine).
A healthy diet contains a variety of different foods so that the body can get the nutrients it requires to function properly.
Recommendations
World Health Organization
The World Health Organization (WHO) makes the following 5 recommendations with respect to both populations and individuals:[6]- Maintain a healthy weight by eating roughly the same number of calories that your body is using.
- Limit intake of fats. Not more than 30% of the total calories should come from fats. Prefer unsaturated fats to saturated fats. Avoid trans fats.
- Eat at least 400 grams of fruits and vegetables per day (potatoes, sweet potatoes, cassava and other starchy roots do not count). A healthy diet also contains legumes (e.g. lentils, beans), whole grains and nuts.
- Limit the intake of simple sugars to less than 10% of calorie (below 5% of calories or 25 grams may be even better)[7]
- Limit salt / sodium from all sources and ensure that salt is iodized. Less than 5 grams of salt per day can reduce the risk of cardiovascular disease.[8]
Other WHO recommendations include ensuring that foods chosen have sufficient vitamins and certain minerals, avoiding directly poisonous (e.g. heavy metals) and carcinogenic (e.g. benzene) substances, avoiding foods contaminated by human pathogens (e.g. E. coli, tapeworm eggs), and replacing saturated fats with polyunsaturated fats in the diet can reduce the risk of coronary artery disease and diabetes.[8]
United States Department of Agriculture
The Dietary Guidelines for Americans by the United States Department of Agriculture (USDA) recommends three healthy patterns of diet, summarized in table below, for a 2000 kcal diet.[9]It emphasizes both health and environmental sustainability and a flexible approach: the committee that drafted it wrote: "The major findings regarding sustainable diets were that a diet higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in calories and animal-based foods is more health promoting and is associated with less environmental impact than is the current U.S. diet. This pattern of eating can be achieved through a variety of dietary patterns, including the “Healthy U.S.-style Pattern,” the “Healthy Vegetarian Pattern," and the "Healthy Mediterranean-style Pattern".[10] Food group amounts are per day, unless noted per week.
| Food group/subgroup (units) | Healthy U.S. patterns | Healthy Vegetarian patterns | Healthy Med-style patterns |
|---|---|---|---|
| Fruits (cup eq) | 2 | 2 | 2.5 |
| Vegetables (cup eq) | 2.5 | 2.5 | 2.5 |
| Dark green | 1.5/wk | 1.5/wk | 1.5/wk |
| Red/orange | 5.5/wk | 5.5/wk | 5.5/wk |
| Starchy | 5/wk | 5/wk | 5/wk |
| Legumes | 1.5/wk | 3/wk | 1.5/wk |
| Others | 4/wk | 4/wk | 4/wk |
| Grains (oz eq) | 6 | 6.5 | 6 |
| Whole | 3 | 3.5 | 3 |
| Refined | 3 | 3 | 3 |
| Dairy (cup eq) | 3 | 3 | 2 |
| Protein Foods (oz eq) | 5.5 | 3.5 | 6.5 |
| Meat (red and processed) | 12.5/wk | -- | 12.5/wk |
| Poultry | 10.5/wk | -- | 10.5/wk |
| Seafood | 8/wk | -- | 15/wk |
| Eggs | 3/wk | 3/wk | 3/wk |
| Nuts/seeds | 4/wk | 7/wk | 4/wk |
| Processed Soy (including tofu) | 0.5/wk | 8/wk | 0.5/wk |
| Oils (grams) | 27 | 27 | 27 |
| Solid fats limit (grams) | 18 | 21 | 17 |
| Added sugars limit (grams) | 30 | 36 | 29 |
American Heart Association / World Cancer Research Fund / American Institute for Cancer Research
The American Heart Association, World Cancer Research Fund, and American Institute for Cancer Research recommend a diet that consists mostly of unprocessed plant foods, with emphasis a wide range of whole grains, legumes, and non-starchy vegetables and fruits. This healthy diet is full of a wide range of various non-starchy vegetables and fruits, that provide different colors including red, green, yellow, white, purple, and orange. They note that tomato cooked with oil, allium vegetables like garlic, and cruciferous vegetables like cauliflower, provide some protection against cancer. This healthy diet is low in energy density, which may protect against weight gain and associated diseases. Finally, limiting consumption of sugary drinks, limiting energy rich foods, including “fast foods” and red meat, and avoiding processed meats improves health and longevity. Overall, researchers and medical policy conclude that this healthy diet can reduce the risk of chronic disease and cancer.[11][12]In children, consuming less than 25 grams of added sugar (100 calories) is recommended per day.[13] Other recommendations include no extra sugars in those under 2 years old and less than one soft drink per week.[13] As of 2017, decreasing total fat is no longer recommended, but instead, the recommendation to lower risk of cardiovascular disease is to increase consumption of monounsaturated fats and polyunsaturated fats, while decreasing consumption of saturated fats.[14]
Harvard School of Public Health
The Nutrition Source of Harvard School of Public Health makes the following 10 recommendations for a healthy diet:[15]- Choose good carbohydrates: whole grains (the less processed the better), vegetables, fruits and beans. Avoid white bread, white rice, and the like as well as pastries, sugared sodas, and other highly processed food.[16]
- Pay attention to the protein package: good choices include fish, poultry, nuts, and beans. Try to avoid red meat.[17]
- Choose foods containing healthy fats. Plant oils, nuts, and fish are the best choices. Limit consumption of saturated fats, and avoid foods with trans fat.[15]
- Choose a fiber-filled diet which includes whole grains, vegetables, and fruits.[18]
- Eat more vegetables and fruits—the more colorful and varied, the better.[15]
- Include adequate amounts of calcium in the diet; however, milk is not the best or only source. Good sources of calcium are collards, bok choy, fortified soy milk, baked beans, and supplements containing calcium and vitamin D.[19]
- Prefer water over other beverages. Avoid sugary drinks, and limit intake of juices and milk. Coffee, tea, artificially-sweetened drinks, 100-percent fruit juices, low-fat milk and alcohol can fit into a healthy diet but are best consumed in moderation. Sports drinks are recommended only for people who exercise more than an hour at a stretch to replace substances lost in sweat.[20]
- Limit salt intake. Choose more fresh foods, instead of processed ones.[15]
- Drink alcohol in moderation. Doing so has health benefits, but is not recommended for everyone.[15]
- Consider intake of daily multivitamin and extra vitamin D, as these have potential health benefits.[15]
Others
David L. Katz, who reviewed the most prevalent popular diets in 2014, noted:The weight of evidence strongly supports a theme of healthful eating while allowing for variations on that theme. A diet of minimally processed foods close to nature, predominantly plants, is decisively associated with health promotion and disease prevention and is consistent with the salient components of seemingly distinct dietary approaches. Efforts to improve public health through diet are forestalled not for want of knowledge about the optimal feeding of Homo sapiens but for distractions associated with exaggerated claims, and our failure to convert what we reliably know into what we routinely do. Knowledge in this case is not, as of yet, power; would that it were so.[21]Marion Nestle expresses the mainstream view among scientists who study nutrition:[22]:10
The basic principles of good diets are so simple that I can summarize them in just ten words: eat less, move more, eat lots of fruits and vegetables. For additional clarification, a five-word modifier helps: go easy on junk foods. Follow these precepts and you will go a long way toward preventing the major diseases of our overfed society—coronary heart disease, certain cancers, diabetes, stroke, osteoporosis, and a host of others.... These precepts constitute the bottom line of what seem to be the far more complicated dietary recommendations of many health organizations and national and international governments—the forty-one “key recommendations” of the 2005 Dietary Guidelines, for example. ... Although you may feel as though advice about nutrition is constantly changing, the basic ideas behind my four precepts have not changed in half a century. And they leave plenty of room for enjoying the pleasures of food.[23]:22
For specific conditions
In addition to dietary recommendations for the general population, there are many specific diets that have primarily been developed to promote better health in specific population groups, such as people with high blood pressure (as in low sodium diets or the more specific DASH diet), or people who are overweight or obese (in weight control diets). However, some of them may have more or less evidence for beneficial effects in normal people as well.Hypertension
A low sodium diet is beneficial for people with high blood pressure. A Cochrane review published in 2008 concluded that a long term (more than 4 weeks) low sodium diet has a useful effect to reduce blood pressure, both in people with hypertension and in people with normal blood pressure.[24]The DASH diet (Dietary Approaches to Stop Hypertension) is a diet promoted by the National Heart, Lung, and Blood Institute (part of the NIH, a United States government organization) to control hypertension. A major feature of the plan is limiting intake of sodium,[25] and the diet also generally encourages the consumption of nuts, whole grains, fish, poultry, fruits, and vegetables while lowering the consumption of red meats, sweets, and sugar. It is also "rich in potassium, magnesium, and calcium, as well as protein".
The Mediterranean diet, which includes limiting consumption of red meat and using olive oil in cooking, has also been shown to improve cardiovascular outcomes.[26]
Obesity
Weight control diets aim to maintain a controlled weight. In most cases, those who are overweight or obese use dieting in combination with physical exercise to lose weight.Diets to promote weight loss are divided into four categories: low-fat, low-carbohydrate, low-calorie, and very low calorie.[27] A meta-analysis of six randomized controlled trials found no difference between the main diet types (low calorie, low carbohydrate, and low fat), with a 2–4 kilogram weight loss in all studies.[27] At two years, all calorie-reduced diet types cause equal weight loss regardless of the macronutrients emphasized.[28]
Gluten, a mixture of proteins found in wheat and related grains including barley, rye, oat, and all their species and hybrids (such as spelt, kamut, and triticale),[29] causes health problems for those with gluten-related disorders, including celiac disease, non-celiac gluten sensitivity, gluten ataxia, dermatitis herpetiformis, and wheat allergy.[30] In these people, the gluten-free diet is the only available treatment.[31][32][33]
Reduced disease risk
There may be a relationship between lifestyle including food consumption and potentially lowering the risk of cancer or other chronic diseases. A diet high in fruits and vegetables appears to decrease the risk of cardiovascular disease and death but not cancer.[34]A healthy diet may consist mostly of whole plant foods, with limited consumption of energy dense foods, red meat, alcoholic drinks and salt while reducing consumption of sugary drinks, and processed meat.[35] A healthy diet may contain non-starchy vegetables and fruits, including those with red, green, yellow, white, purple or orange pigments. Tomato cooked with oil, allium vegetables like garlic, and cruciferous vegetables like cauliflower "probably" contain compounds which are under research for their possible anti-cancer activity.[11][12]
A healthy diet is low in energy density, lowering caloric content, thereby possibly inhibiting weight gain and lowering risk against chronic diseases.[11][12][36] Chronic Western diseases are associated with pathologically increased IGF-1 levels. Findings in molecular biology and epidemiologic data suggest that milk consumption is a promoter of chronic diseases of Western nations, including atherosclerosis, carcinogenesis and neurodegenerative diseases.[37]
Unhealthy diets
The Western pattern diet which is typically eaten by Americans and increasingly adapted by people in the developing world as they leave poverty is unhealthy: it is "rich in red meat, dairy products, processed and artificially sweetened foods, and salt, with minimal intake of fruits, vegetables, fish, legumes, and whole grains."[38]An unhealthy diet is a major risk factor for a number of chronic diseases including: high blood pressure, diabetes, abnormal blood lipids, overweight/obesity, cardiovascular diseases, and cancer.[39]
The WHO estimates that 2.7 million deaths are attributable to a diet low in fruits and vegetables every year.[39] Globally it is estimated to cause about 19% of gastrointestinal cancer, 31% of ischaemic heart disease, and 11% of strokes,[4] thus making it one of the leading preventable causes of death worldwide.[40]
Popular diets
Popular diets, often referred to as fad diets, make promises of weight loss or other health advantages such as longer life without backing by solid science, and in many cases are characterized by highly restrictive or unusual food choices.[23]:296[41] Celebrity endorsements (including celebrity doctors) are frequently associated with popular diets, and the individuals who develop and promote these programs often profit handsomely.[22]:11–12[42]Public health
Fears of high cholesterol were frequently voiced up until the mid-1990s. However, more recent research has shown that the distinction between high- and low-density lipoprotein ('good' and 'bad' cholesterol, respectively) must be addressed when speaking of the potential ill effects of cholesterol. Different types of dietary fat have different effects on blood levels of cholesterol. For example, polyunsaturated fats tend to decrease both types of cholesterol; monounsaturated fats tend to lower LDL and raise HDL; saturated fats tend to either raise HDL, or raise both HDL and LDL;[43][44] and trans fat tend to raise LDL and lower HDL.While dietary cholesterol is only found in animal products such as meat, eggs, and dairy, studies have not found a link between eating cholesterol and blood levels of cholesterol.[45]
Vending machines in particular have come under fire as being avenues of entry into schools for junk food promoters. However, there is little in the way of regulation and it is difficult for most people to properly analyze the real merits of a company referring to itself as "healthy." Recently, the Committee of Advertising Practice in the United Kingdom launched a proposal to limit media advertising for food and soft drink products high in fat, salt or sugar.[46] The British Heart Foundation released its own government-funded advertisements, labeled "Food4Thought", which were targeted at children and adults to discourage unhealthy habits of consuming junk food.[47]
From a psychological and cultural perspective, a healthier diet may be difficult to achieve for people with poor eating habits.[48] This may be due to tastes acquired in childhood and preferences for sugary, salty and/or fatty foods.[49]
