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 to 36.
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.
Certain vegetable products have high saturated fat content, such as coconut oil, cottonseed
oil, palm kernel oil and chocolate.
Many prepared foods are high in saturated fat content, such as pizza, dairy desserts,
bacon and sausage.
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 and dairy products.
The saturated fat in meat, eggs, chocolate, and nuts is primarily the triglycerides of
palmitic and stearic acids.
Examples of saturated fatty acids
Some common examples of fatty acids: Butyric acid with 4 carbon atoms
Lauric acid with 12 carbon atoms Myristic acid with 14 carbon atoms
Palmitic acid with 16 carbon atoms Stearic acid with 18 carbon atoms
Association with diseases Since the 1950s, it has been commonly believed
that consumption of foods containing high amounts of saturated fatty acids 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.
Cardiovascular disease
A 2010 meta-analysis of 21 studies examined the effects of dietary saturated fat intake
and found that ″there is no significant evidence for concluding that dietary saturated
fat is associated with an increased risk of CHD or CVD.″
Meanwhile, a 2014 systematic review and meta-analysis in the Annals of Internal Medicine, of 72
published studies totalling 530,525 participants, looked 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.
The authors of the review concluded that their findings ″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.″
However, Walter Willett, chair of the Department of Nutrition at Harvard School of Public Health,
warns that the conclusions from this study are seriously misleading, as the analysis
contains major errors and omissions:
″This paper is bound to cause confusion.
A central issue is what replaces saturated fat if someone reduces the amount of saturated
fat in their diet.
If it is replaced with refined starch or sugar, which are the largest sources of calories
in the U.S. diet, then the risk of heart disease remains the same.
However, if saturated fat is replaced with polyunsaturated fat or monounsaturated fat
in the form of olive oil, nuts and probably other plant oils, we have much evidence that
risk will be reduced″.
Separately, it was noted that because some of the pooled studies involved people with
cardiovascular risk factors or with cardiovascular disease, the results may not necessarily apply
to the population at large.
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.
Furthermore, leading medical, heart-health, and governmental authorities, such as the
World Health Organization, the American Dietetic Association, the Dietitians of Canada, the
British Dietetic Association, American Heart Association, the British Heart Foundation,
the World Heart Federation, the British National Health Service, the United States Food and
Drug Administration, and the European Food Safety Authority advise that saturated fat
is a risk factor for cardiovascular disease.
Numerous systematic reviews have examined the relationship between saturated fat and
cardiovascular disease: 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.
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.
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.
Abnormal blood lipid levels, that is high total cholesterol, high levels of triglycerides,
high levels of low-density lipoprotein or low levels of high-density lipoprotein cholesterol
are all associated with increased risk of heart disease and stroke.
Meta-analyses have found a significant relationship between saturated fat and serum cholesterol
levels.
High total cholesterol levels, which may be caused by many factors, are associated with
an increased risk of cardiovascular disease.
However, other indicators measuring cholesterol such as high total/HDL cholesterol ratio are
more predictive than total serum cholesterol.
In a study of myocardial infarction in 52 countries, the ApoB/ApoA1 ratio was the strongest
predictor of CVD among all risk factors.
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.
Different saturated fatty acids have differing effects on various lipid levels.
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.
However two subsequent reviews have found weak or insignificant associations of saturated
fat intake and breast cancer risk, and note the prevalence of confounding factors.
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.
Ovarian cancer A meta-analysis of eight observational studies
published in 2001 found a statistically significant positive relationship between saturated fat
and ovarian cancer.
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.
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 and palmitic acid and dietary
myristic and palmitic saturated fatty acids and serum palmitic combined with alpha-tocopherol
supplementation 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.
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.
Dietary recommendations Recommendations to reduce or limit dietary
intake of saturated fats are made by Health Canada, the US Department of Health and Human
Services, the UK Food Standards Agency, the Australian Department of Health and Aging,
the Singapore Government Health Promotion Board, the Indian Government Citizens Health
Portal, the New Zealand Ministry of Health, the Food and Drugs Board Ghana, the Republic
of Guyana Ministry of Health, and Hong Kong's Centre for Food Safety.
A 2004 statement released by the Centers for Disease Control determined that "Americans
need to continue working to reduce saturated fat intake…"
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.
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.
In 2003, the World Health Organization and Food and Agriculture Organization 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.
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."
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.
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.
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.
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 will be present between adjacent carbon atoms of
the tail.
See also References
Further reading