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A saturated fat is a fat that consists of triglycerides containing only saturated fatty acids. Saturated fatty acids have no double bonds between the individual carbon atoms of the fatty acid chain. That is, the chain of carbon atoms is fully "saturated" with hydrogen atoms. There are many kinds of naturally occurring saturated fatty acids, which differ mainly in number of carbon atoms, from 3 carbons (propionic acid) to 36 (hexatriacontanoic acid).
Various fats contain different proportions of saturated and unsaturated fat. Examples of foods containing a high proportion of saturated fat include animal fat products such as cream, cheese, butter, ghee, suet, tallow, lard, and fatty meats.[1] Certain vegetable products have high saturated fat content, such as coconut oil, cottonseed oil, palm kernel oil and chocolate[citation needed]. Many prepared foods are high in saturated fat content, such as pizza, dairy desserts, bacon and sausage.[2][3]
A number of systematic reviews have examined the relationship between saturated fat and cardiovascular disease and have come to different conclusions:
A 2014 systematic review looking at observational studies of dietary intake of fatty acids, observational studies of measured fatty acid levels in the blood, and intervention studies of polyunsaturated fat supplementation concludes that the finding ″do not support cardiovascular guidelines that promote high consumption of long-chain omega-3 and omega-6 and polyunsaturated fatty acids and suggest reduced consumption of total saturated fatty acids.″[20] Researchers acknowledged that despite their results, further research is necessary, especially in people who are initially healthy. Until the picture becomes clearer, experts recommend people stick to the current guidelines on fat consumption.[21]
While many studies have found that including polyunsaturated fats in the diet in place of saturated fats produces more beneficial CVD outcomes, the effects of substituting monounsaturated fats or carbohydrates are unclear.[33][34]
There are strong, consistent, and graded relationships between saturated fat intake, blood cholesterol levels, and the mass occurrence of cardiovascular disease. The relationships are accepted as causal.[40][41] Abnormal blood lipid levels, that is high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol) cholesterol are all associated with increased risk of heart disease and stroke.[16]
Meta-analyses have found a significant relationship between saturated fat and serum cholesterol levels.[42] High total cholesterol levels, which may be caused by many factors, are associated with an increased risk of cardiovascular disease.[43][44] However, other indicators measuring cholesterol such as high total/HDL cholesterol ratio are more predictive than total serum cholesterol.[44] In a study of myocardial infarction in 52 countries, the ApoB/ApoA1 (related to LDL and HDL, respectively) ratio was the strongest predictor of CVD among all risk factors.[45] There are other pathways involving obesity, triglyceride levels, insulin sensitivity, endothelial function, and thrombogenicity, among others, that play a role in CVD, although it seems, in the absence of an adverse blood lipid profile, the other known risk factors have only a weak atherogenic effect.[46] Different saturated fatty acids have differing effects on various lipid levels.[47]
Various fats contain different proportions of saturated and unsaturated fat. Examples of foods containing a high proportion of saturated fat include animal fat products such as cream, cheese, butter, ghee, suet, tallow, lard, and fatty meats.[1] Certain vegetable products have high saturated fat content, such as coconut oil, cottonseed oil, palm kernel oil and chocolate[citation needed]. Many prepared foods are high in saturated fat content, such as pizza, dairy desserts, bacon and sausage.[2][3]
Fat profiles
While nutrition labels regularly combine them, the saturated fatty acids appear in different proportions among food groups. Lauric and myristic acids are most commonly found in "tropical" oils (e.g., palm kernel, coconut) and dairy products. The saturated fat in meat, eggs, cacao, and nuts is primarily the triglycerides of palmitic and stearic acids.| Food | Lauric acid | Myristic acid | Palmitic acid | Stearic acid |
|---|---|---|---|---|
| Coconut oil | 47% | 18% | 9% | 3% |
| Palm oil | 48% | 1% | 44% | 5% |
| Butter | 3% | 11% | 29% | 13% |
| Ground beef | 0% | 4% | 26% | 15% |
| Salmon | 0% | 1% | 29% | 3% |
| Egg yolks | 0% | 0.3% | 27% | 10% |
| Cashews | 2% | 1% | 10% | 7% |
| Soybean oil | 0% | 0% | 11% | 4% |
Examples of saturated fatty acids
Some common examples of fatty acids:- Butyric acid with 4 carbon atoms (contained in butter)
- Lauric acid with 12 carbon atoms (contained in coconut oil, palm kernel oil, and breast milk)
- Myristic acid with 14 carbon atoms (contained in cow's milk and dairy products)
- Palmitic acid with 16 carbon atoms (contained in palm oil and meat)
- Stearic acid with 18 carbon atoms (also contained in meat and cocoa butter)
Association with diseases
Since the 1950s, it has been commonly believed that consumption of foods containing high amounts of saturated fatty acids (including meat fats, milk fat, butter, lard, coconut oil, palm oil, and palm kernel oil) is potentially less healthy than consuming fats with a lower proportion of saturated fatty acids. Sources of lower saturated fat but higher proportions of unsaturated fatty acids include olive oil, peanut oil, canola oil, avocados, safflower, corn, sunflower, soy, and cottonseed oils.[10]Cardiovascular disease
Leading medical, heart-health, and governmental authorities, such as the World Health Organization,[11] the American Dietetic Association,[12] the Dietitians of Canada,[12] the British Dietetic Association,[13] American Heart Association,[14] the British Heart Foundation,[15] the World Heart Federation,[16] the British National Health Service,[17] the United States Food and Drug Administration,[18] and the European Food Safety Authority[19] advise that saturated fat is a risk factor for cardiovascular disease (CVD).A number of systematic reviews have examined the relationship between saturated fat and cardiovascular disease and have come to different conclusions:
A 2014 systematic review looking at observational studies of dietary intake of fatty acids, observational studies of measured fatty acid levels in the blood, and intervention studies of polyunsaturated fat supplementation concludes that the finding ″do not support cardiovascular guidelines that promote high consumption of long-chain omega-3 and omega-6 and polyunsaturated fatty acids and suggest reduced consumption of total saturated fatty acids.″[20] Researchers acknowledged that despite their results, further research is necessary, especially in people who are initially healthy. Until the picture becomes clearer, experts recommend people stick to the current guidelines on fat consumption.[21]
| Harcombe, 2015[22] | No reduction in CHD and all-cause mortality were observed when replacing saturated fat with polyunsaturated fat, even though reductions in serum cholesterol were observed. |
| Schwab, 2014[23] | There was convincing evidence that partial replacement of saturated fat with polyunsaturated fat decreases the risk of cardiovascular diseases, especially in men. |
| Hooper, 2011[24] | Reducing saturated fat in diets did not reduce mortality, despite reducing the risk of having a cardiovascular event by 14 percent. |
| Micha, 2010[25] | Based on consistent evidence from human studies, replacing SFA with polyunsaturated fat modestly lowers coronary heart disease risk, with ~10% risk reduction for a 5% energy substitution; whereas replacing SFA with carbohydrate has no benefit and replacing SFA with monounsaturated fat has uncertain effects. |
| Mozaffarian, 2010[26] | These findings provide evidence that consuming polyunsaturated fats (PUFA) in place of SFA reduces Coronary Heart Disease (CHD) events in randomized controlled trials (RCT). Replacing saturated fats with PUFAs as percentage of calories strongly reduced CHD mortality. |
| Siri-Tarino, 2010[27] | 5–23 years of follow-up of 347,747 subjects, 11,006 developed CHD or stroke. A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD. |
| Danaei, 2009[28] | Low PUFA intake has an 1-5% Increased risk of ischemic heart disease: Low dietary PUFA (in replacement of SFA). age 30–44 Increase in RR 1.05. |
| Mente, 2009[29] | Single-nutrient RCTs have yet to evaluate whether reducing saturated fatty acid intake lowers the risk of CHD events. For polyunsaturated fatty acid intake, most of the RCTs have not been adequately powered and did not find a significant reduction in CHD outcomes. |
| Skeaff, 2009[30] | Intake of SFA was not significantly associated with CHD mortality, with a RR of 1.14. Moreover, there was no significant association with CHD death. Intake of PUFA was strongly significantly associated with CHD mortality, with a RR of 1.25. The Health Professionals Follow-up Study and the EUROASPIRE study results mirrored those of total PUFA; intake of linoleic acid was significantly associated with CHD mortality. |
| Jakobsen, 2009[31] | "The associations suggest that replacing saturated fatty acids with polyunsaturated fatty acids rather than monounsaturated fatty acids or carbohydrates prevents CHD over a wide range of intakes." |
| Van Horn, 2008[32] | 25-35% fats but <7% SFA and TFA reduces risk. |
While many studies have found that including polyunsaturated fats in the diet in place of saturated fats produces more beneficial CVD outcomes, the effects of substituting monounsaturated fats or carbohydrates are unclear.[33][34]
Dyslipidemia
The consumption of saturated fat is generally considered a risk factor for dyslipidemia, which in turn is a risk factor for some types of cardiovascular disease.[35][36][37][38][39]There are strong, consistent, and graded relationships between saturated fat intake, blood cholesterol levels, and the mass occurrence of cardiovascular disease. The relationships are accepted as causal.[40][41] Abnormal blood lipid levels, that is high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol) cholesterol are all associated with increased risk of heart disease and stroke.[16]
Meta-analyses have found a significant relationship between saturated fat and serum cholesterol levels.[42] High total cholesterol levels, which may be caused by many factors, are associated with an increased risk of cardiovascular disease.[43][44] However, other indicators measuring cholesterol such as high total/HDL cholesterol ratio are more predictive than total serum cholesterol.[44] In a study of myocardial infarction in 52 countries, the ApoB/ApoA1 (related to LDL and HDL, respectively) ratio was the strongest predictor of CVD among all risk factors.[45] There are other pathways involving obesity, triglyceride levels, insulin sensitivity, endothelial function, and thrombogenicity, among others, that play a role in CVD, although it seems, in the absence of an adverse blood lipid profile, the other known risk factors have only a weak atherogenic effect.[46] Different saturated fatty acids have differing effects on various lipid levels.[47]
Cancer
Breast cancer
A meta-analysis published in 2003 found a significant positive relationship in both control and cohort studies between saturated fat and breast cancer.[48] However two subsequent reviews have found weak or insignificant associations of saturated fat intake and breast cancer risk,[49][50] and note the prevalence of confounding factors.[49][51]Colorectal cancer
A systematic literature review published by the World Cancer Research Fund and the American Institute for Cancer Research in 2007 found limited but consistent evidence for a positive relationship between animal fat and colorectal cancer.[52]Ovarian cancer
A meta-analysis of eight observational studies published in 2001 found a statistically significant positive relationship between saturated fat and ovarian cancer.[53] However, a 2013 study found that a pooled analysis of 12 cohort studies observed no association between total fat intake and ovarian cancer risk. Further analysis revealed that omega-3 fatty acids were protective against ovarian cancer and that trans fats were a risk factor.[54] This study revealed that histological subtypes should be examined in determining the impact of dietary fat on ovarian cancer, rather than an oversimplified focus on total fat intake.Prostate cancer
Some researchers have indicated that serum myristic acid[55][56] and palmitic acid[56] and dietary myristic[57] and palmitic[57] saturated fatty acids and serum palmitic combined with alpha-tocopherol supplementation[55] are associated with increased risk of prostate cancer in a dose-dependent manner.
These associations may, however, reflect differences in intake or metabolism of these fatty acids between the precancer cases and controls, rather than being an actual cause.[56]
A 2004 statement released by the Centers for Disease Control (CDC) determined that "Americans need to continue working to reduce saturated fat intake…"[69] In addition, reviews by the American Heart Association led the Association to recommend reducing saturated fat intake to less than 7% of total calories according to its 2006 recommendations.[70][71] This concurs with similar conclusions made by the US Department of Health and Human Services, which determined that reduction in saturated fat consumption would positively affect health and reduce the prevalence of heart disease.[72]
In 2003, the World Health Organization (WHO) and Food and Agriculture Organization (FAO) expert consultation report concluded that "intake of saturated fatty acids is directly related to cardiovascular risk. The traditional target is to restrict the intake of saturated fatty acids to less than 10% of daily energy intake and less than 7% for high-risk groups. If populations are consuming less than 10%, they should not increase that level of intake. Within these limits, intake of foods rich in myristic and palmitic acids should be replaced by fats with a lower content of these particular fatty acids. In developing countries, however, where energy intake for some population groups may be inadequate, energy expenditure is high and body fat stores are low (BMI <18.5 kg/m2). The amount and quality of fat supply has to be considered keeping in mind the need to meet energy requirements. Specific sources of saturated fat, such as coconut and palm oil, provide low-cost energy and may be an important source of energy for the poor."[73]
Dr. German and Dr. Dillard of University of California and Nestle Research Center in Switzerland, in their 2004 review, pointed out that "no lower safe limit of specific saturated fatty acid intakes has been identified" and recommended that the influence of varying saturated fatty acid intakes against a background of different individual lifestyles and genetic backgrounds should be the focus in future studies.[74]
Blanket recommendations to lower saturated fat were criticized at a 2010 conference debate of the American Dietetic Association for focusing too narrowly on reducing saturated fats rather than emphasizing increased consumption of healthy fats and unrefined carbohydrates. Concern was expressed over the health risks of replacing saturated fats in the diet with refined carbohydrates, which carry a high risk of obesity and heart disease, particularly at the expense of polyunsaturated fats which may have health benefits. None of the panelists recommended heavy consumption of saturated fats, emphasizing instead the importance of overall dietary quality to cardiovascular health.[75]
It should be noted, as this is the defining factor of saturated fats, that the two-dimensional illustration has implicit hydrogens bonded to each of the carbon atoms in the polycarbon tail of the myristic acid molecule (there are 13 carbons in the tail, 14 carbons in the entire molecule).
Carbon atoms are also implicitly drawn, as they are portrayed as intersections between two straight lines. "Saturated," in general, refers to a maximum number of hydrogens bonded to each carbon of the polycarbon tail as allowed by the Octet Rule. This also means that only single bonds (sigma bonds) will be present between adjacent carbon atoms of the tail.
Bones
Mounting evidence indicates that the amount and type of fat in the diet can have important effects on bone health. Most of this evidence is derived from animal studies. The data from one study indicated that bone mineral density is negatively associated with saturated fat intake, and that men may be particularly vulnerable.[58]Dietary recommendations
Recommendations to reduce or limit dietary intake of saturated fats are made by Health Canada,[59] the US Department of Health and Human Services,[60] the UK Food Standards Agency,[61] the Australian Department of Health and Aging,[62] the Singapore Government Health Promotion Board,[63] the Indian Government Citizens Health Portal,[64] the New Zealand Ministry of Health,[65] the Food and Drugs Board Ghana,[66] the Republic of Guyana Ministry of Health,[67] and Hong Kong's Centre for Food Safety.[68]A 2004 statement released by the Centers for Disease Control (CDC) determined that "Americans need to continue working to reduce saturated fat intake…"[69] In addition, reviews by the American Heart Association led the Association to recommend reducing saturated fat intake to less than 7% of total calories according to its 2006 recommendations.[70][71] This concurs with similar conclusions made by the US Department of Health and Human Services, which determined that reduction in saturated fat consumption would positively affect health and reduce the prevalence of heart disease.[72]
In 2003, the World Health Organization (WHO) and Food and Agriculture Organization (FAO) expert consultation report concluded that "intake of saturated fatty acids is directly related to cardiovascular risk. The traditional target is to restrict the intake of saturated fatty acids to less than 10% of daily energy intake and less than 7% for high-risk groups. If populations are consuming less than 10%, they should not increase that level of intake. Within these limits, intake of foods rich in myristic and palmitic acids should be replaced by fats with a lower content of these particular fatty acids. In developing countries, however, where energy intake for some population groups may be inadequate, energy expenditure is high and body fat stores are low (BMI <18.5 kg/m2). The amount and quality of fat supply has to be considered keeping in mind the need to meet energy requirements. Specific sources of saturated fat, such as coconut and palm oil, provide low-cost energy and may be an important source of energy for the poor."[73]
Dr. German and Dr. Dillard of University of California and Nestle Research Center in Switzerland, in their 2004 review, pointed out that "no lower safe limit of specific saturated fatty acid intakes has been identified" and recommended that the influence of varying saturated fatty acid intakes against a background of different individual lifestyles and genetic backgrounds should be the focus in future studies.[74]
Blanket recommendations to lower saturated fat were criticized at a 2010 conference debate of the American Dietetic Association for focusing too narrowly on reducing saturated fats rather than emphasizing increased consumption of healthy fats and unrefined carbohydrates. Concern was expressed over the health risks of replacing saturated fats in the diet with refined carbohydrates, which carry a high risk of obesity and heart disease, particularly at the expense of polyunsaturated fats which may have health benefits. None of the panelists recommended heavy consumption of saturated fats, emphasizing instead the importance of overall dietary quality to cardiovascular health.[75]
Molecular description
It should be noted, as this is the defining factor of saturated fats, that the two-dimensional illustration has implicit hydrogens bonded to each of the carbon atoms in the polycarbon tail of the myristic acid molecule (there are 13 carbons in the tail, 14 carbons in the entire molecule).
Carbon atoms are also implicitly drawn, as they are portrayed as intersections between two straight lines. "Saturated," in general, refers to a maximum number of hydrogens bonded to each carbon of the polycarbon tail as allowed by the Octet Rule. This also means that only single bonds (sigma bonds) will be present between adjacent carbon atoms of the tail.
