Fats
Saturated fats have been demonized since Ansel Keys came out with his 7 Country Study. From this came the “Diet Heart Hypothesis” which espouses that saturated fat raises cholesterol which leads to heart disease. This theory was adopted by the first governmental dietary recommendation panel and led to the “Food Pyramid”. This has led to the recommendation to eat a low saturated fat, medium protein, high carbohydrate diet. It can be demonstrated that the 7 Country Study was highly flawed and it was not reproducible. Keyes actually had data from 23 countries but cherry picked seven countries that aligned with his theory and ignored the rest. In the Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73)
“Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid [an Omega-6 polyunsaturated fat] effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid.”
The study was never originally published. When asked, the researcher stated that the results were “disappointing”. Here are the key details:
The MCE was led by Dr. Ivan Frantz Jr. of the University of Minnesota Medical School and funded by the National Heart, Lung and Blood Institute.
It studied the diets of over 9,000 participants in state mental hospitals and a nursing home.
Half the participants were fed meals rich in saturated fats from milk, cheese, and beef.
The other half ate a diet where much of the saturated fat was replaced with corn oil (an unsaturated fat).
The study aimed to show that replacing saturated fat with polyunsaturated fat would protect against heart disease and lower mortality.
Despite being one of the largest controlled clinical dietary trials of its kind, the data were never fully analyzed or published at the time.
Several years ago, Christopher E. Ramsden, a medical investigator at the National Institutes of Health, learned about this overlooked study.
Dr. Robert Frantz, the son of the lead researcher and a cardiologist at Mayo Clinic, found the original data in a dusty box in his father's basement.
The data were then turned over to Dr. Ramsden for analysis.
The analysis showed that while the low-saturated fat diet reduced cholesterol by 14%, it did not reduce mortality.
The analysis showed that while the low-saturated fat diet reduced cholesterol by 14%, it did not reduce mortality.
Surprisingly, the study found that the greater the drop in cholesterol, the higher the risk of death during the trial.
These findings challenge conventional dietary recommendations that advise a diet low in saturated fat to decrease heart risk.
The rediscovery and analysis of this long-lost data have raised new questions about longstanding dietary advice regarding saturated fats and heart health.
Fats are an essential macronutrient that plays an important role in the body, including energy storage, insulation, and cell membrane structure. There are several main types of dietary fats:
Unsaturated Fats
Unsaturated fats are liquid at room temperature and come mainly from plant sources. There are two main types:
Monounsaturated Fats
Monounsaturated fats can help lower bad LDL cholesterol and maintain good HDL cholesterol levels. Sources include:
- Olive oil
- Avocados
- Nuts like almonds, cashews, and peanuts
Polyunsaturated Fats
Key types are omega-3 and omega-6 fatty acids. Sources include:
- Fatty fish like salmon and mackerel
- Walnuts
- Flaxseeds
- Sunflower, corn, and soybean oils
Saturated Fats
Saturated fats are solid at room temperature and come mostly from animal sources. They can raise LDL cholesterol levels. Sources include:
- Fatty cuts of meat
- Full-fat dairy products
- Coconut and palm oils
- Butter
Trans Fats
Trans fats are considered the unhealthiest type of fat. They are another type of polyunsaturated fats. They raise bad LDL cholesterol and lower good HDL cholesterol. Sources include:
- Partially hydrogenated oils
- Some fried and processed foods
- Small amounts occur naturally in some meats and dairy
The Truth About Saturated Fats
The evidence and research, from the time the Diet Heart Hypothesis was developed, has clearly shown that saturated fat is absolutely fine to eat and that polyunsaturated fats (the Omega-6 fatty acids, such as linoleic acid) found in seed oils are the fats that are bad for you. Yes, seed oils will lower LDL. However, LDL does not cause cardiovascular disease (see my page on cholesterol).
Most doctors and nutritionists still follow the “Diet Heart Hypothesis”. I am a doctor and the amount of time spent on nutrition in medical school is very limited. Anything taught to us must follow the US government guidelines. See the research articles provided to see that the government guidelines need to be re-evaluated and that saturated fats are good for you. It is carbohydrates and polyunsaturated fats in excess amounts that are harming us.
Chowdhury R, Warnakula S, Setor Kunutsor S, Crowe F, Ward H, Johnson L et al. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med 2014;160:398-406.
“The systematic review and meta-analysis, published in the Annals of Internal Medicine, included studies involving more than 600 000 people in 18 countries. The researchers found no association between total saturated fatty acid consumption and coronary risk when they analysed 32 observational studies of fatty acids in dietary intake and 17 observational studies of fatty acid biomarkers. However, total intake of trans fats, found in some processed foods, was associated with coronary disease risk. The researchers, led by Rajiv Chowdhury from the University of Cambridge, also found that higher intake of polyunsaturated fats did not offer any protection against heart disease. They found some evidence that circulating levels of two main types of long chain omega 3 polyunsaturated fatty acids and arachidonic acid are each associated with lower coronary risk. However, their meta-analysis of 27 randomised trialsinvolving more than 100 000 participantsindicated that taking supplements with these nutrients did not significantly reduce the risk of poor coronary outcomes.”
Siri-Tarino PW, Sun Q, Hu FB, et al. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am. J. Clin. Nutr. 2010;91(3):535–546.
“During 5–23 y of follow-up of 347,747 subjects, 11,006 developed CHD or stroke. Intake of saturated fat was not associated with an increased risk of CHD, stroke, or CVD, 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. More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat.”
Ravnskov U. A hypothesis out-of-date The diet–heart idea. J. Clin. Epidemiology. 2002;55(11):1057–1063.
“A large number of scientific studies contradict the hypothesis that dietary fat and high cholesterol play a major role in the causation of atherosclerosis and cardiovascular disease. Readers may probably object that I have preferably picked contradictory studies out of a huge number of supportive ones. However, a thorough examination of the literature in this area [1] has convinced me that most studies are either useless for determining causality, or they are contradictory. But even if many studies were supportive, a valid hypothesis should withstand all attempts of falsification. One single study that falsifies it and which is based on verifiable observations should suffice for its rejection. There are many, more or less probable, alternative hypotheses about the causation of atherosclerosis and cardiovascular disease, but the maintenance of the diet–heart hypothesis by prestigious and powerful scientists and organizations retard their exploration by turning away intellectual and financial resources. Worse is the fact, that any new discovery is twisted and bent to tally with the current concept, not to mention the negative effects on public health, food production, and the health and general well-being of millions of people. It would be a great contribution to science and mankind if influential institutions could break the vicious cycle by supporting researchers who create hypotheses that fit their data, instead of researchers who interpret their data to fit a predetermined hypothesis.”
Malhotra A, Redberg RF, Meier P. Saturated fat does not clog the arteries: coronary heart disease is a chronic inflammatory condition, the risk of which can be effectively reduced from healthy lifestyle interventions. Br. J. Sports Med. 2017;51(15):1111.
“Coronary artery disease pathogenesis and treatment urgently requires a paradigm shift. Despite popular belief among doctors and the public, the conceptual model of dietary saturated fat clogging a pipe is just plain wrong. A landmark systematic review and meta-analysis of observational studies showed no association between saturated fat consumption and (1) all-cause mortality, (2) coronary heart disease (CHD), (3) CHD mortality, (4) ischaemic stroke or (5) type 2 diabetes in healthy adults.1 Similarly in the secondary prevention of CHD there is no benefit from reduced fat, including saturated fat, on myocardial infarction, cardiovascular or all-cause mortality.2 It is instructive to note that in an angiographic study of postmenopausal women with CHD, greater intake of saturated fat was associated with less progression of atherosclerosis whereas carbohydrate and polyunsaturated fat intake were associated with greater progression.”
1.Lee JH, Duster M, Roberts T, et al. United States Dietary Trends Since 1800: Lack of Association Between Saturated Fatty Acid Consumption and Non-communicable Diseases. Front. Nutr. 2022;8:748847.
“Processed and ultra-processed foods increased from <5 to >60% of foods. Large increases occurred for sugar, white and whole wheat flour, rice, poultry, eggs, vegetable oils, dairy products, and fresh vegetables. Saturated fats from animal sources declined while polyunsaturated fats from vegetable oils rose. Non-communicable diseases (NCDs) rose over the twentieth century in parallel with increased consumption of processed foods, including sugar, refined flour and rice, and vegetable oils. Saturated fats from animal sources were inversely correlated with the prevalence of NCDs. Conclusions: As observed from the food availability data, processed and ultra-processed foods dramatically increased over the past two centuries, especially sugar, white flour, white rice, vegetable oils, and ready-to-eat meals. These changes paralleled the rising incidence of NCDs, while animal fat consumption was inversely correlated.”
1.Howard BV, Horn LV, Hsia J, et al. Low-Fat Dietary Pattern and Risk of Cardiovascular Disease: The Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006;295(6):655–666.
“Over a mean of 8.1 years, a dietary intervention that reduced total fat intake and increased intakes of vegetables, fruits, and grains did not significantly reduce the risk of CHD, stroke, or CVD in postmenopausal women and achieved only modest effects on CVD risk factors, suggesting that more focused diet and lifestyle interventions may be needed to improve risk factors and reduce CVD risk.”
Grasgruber P, Sebera M, Hrazdira E, et al. Food consumption and the actual statistics of cardiovascular diseases: an epidemiological comparison of 42 European countries. Food Nutr. Res. 2016;60(0):31694.
“The most significant dietary correlate of low CVD risk was high total fat and animal protein consumption.” “Our results do not support the association between CVDs and saturated fat, which is still contained in official dietary guidelines. Instead, they agree with data accumulated from recent studies that link CVD risk with the high glycaemic index/load of carbohydrate-based diets. In the absence of any scientific evidence connecting saturated fat with CVDs, these findings show that current dietary recommendations regarding CVDs should be seriously reconsidered.
Astrup A, Teicholz N, Magkos F, et al. Dietary Saturated Fats and Health: Are the U.S. Guidelines Evidence-Based? Nutrients. 2021;13(10):3305.
“Multiple reviews of the evidence have demonstrated that a recommendation to limit consumption of saturated fats to no more than 10% of total calories is not supported by rigorous scientific studies. Importantly, neither this guideline, nor that for replacing saturated fats with polyunsaturated fats, considers the central issue of the health effects of differing food sources of these fats. The 2020 DGAC review that recommends continuing these recommendations has, in our view, not met the standard of “the preponderance of the evidence” for this decision.”