These days it is commonplace to see headlines in the media proclaiming “Butter is Back” or “Why Full-Fat Dairy May be Better Than Low-Fat” and book titles like “Eat Bacon, Don’t Jog: Get Strong. Get Lean. No Bullshit.” (1,2,3,4,5). What is happening here? We have believed for decades that consuming too much saturated fat leads to clogged arteries and eventually heart attacks or strokes. Have recent studies refuted previous studies? Can we really forget about watching our fat and start to worry more about sugar or some other reputed “poison”?
Headlines sell papers…
It is unfortunate that headlines such as these are the ones that are front and center in our media but it is just such “news” that sells newspapers, magazines and books and makes us want to follow the latest on-line “doctor”. The fact that these proclamations are often based on poorly designed studies or the erroneous interpretation of studies is never pointed out. Confusion is the result. People can certainly be forgiven for embracing a view that supports their eating behaviour. Let’s face it – it is much more comforting to follow advice that approves of your present eating routine than that which seems to be saying that the comfortable mealtime patterns passed down to us from our parents and grandparents are not as healthy as we once believed and that it is time to consider making a lifestyle adjustment.
A little bit about fat….
Before delving more deeply into this topic it is important to understand a few details regarding fats. First of all, saturated fats are associated not only with the development of cardiovascular disease but also with diabetes, some cancers and other chronic diseases (aka lifestyle diseases or diseases of affluence). Almost all of the saturated fat in the diet of human beings comes from animal-based foods such as meat, eggs and dairy products. There are also a few plant-based oils that contain saturated fats. Examples of these are palm oil, palm kernel oil, cocoa butter and coconut oil. Polyunsaturated fat sources include liquid vegetable oils such as peanut oil, safflower oil and corn oil; fatty fish, nuts and seeds.
The “fat” studies….
The main impetus for the saturated fat controversy stems from two meta-analyses published in 2010 and 2014 (6,7). A meta-analysis is a gathering together and review of previous studies on a particular topic. The 2010 meta-analysis reviewed 21 prospective epidemiological studies with the objective of summarizing the evidence related to the association of dietary saturated fat with risk of coronary heart disease (CHD), stroke, and cardiovascular disease. The 2014 meta-analysis reviewed 49 observational studies and 27 randomized, controlled trials with the goal of summarizing the evidence for associations between fatty acids and coronary disease. Neither of these meta-analyses included any new research. The conclusion from these meta-analyses was that saturated fat (media headlines used butter as an example of saturated fat) is only weakly associated with increased total mortality and not associated with cardiovascular disease (6) and that current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats (7).
Problems with the “fat” studies….
There are several problems with the interpretation that resulted from these two meta-analyses. First of all, there is no specific comparison of saturated fat to a single alternative and so it is compared to the standard American diet, a largely unhealthy mix of red and processed meat, trans-fats, refined sugars and grains, processed foods and high sugar beverages (11). Also, improper adjustments were made in the review data. Three studies were adjusted for dietary lipids and almost half the studies were adjusted for serum lipids including cholesterol. Since cholesterol is part of the reason that eating saturated fat leads to cardiovascular disease, adjusting for serum cholesterol will obscure any association there may have been between consumption of saturated fat and cardiovascular problems (9,15). Also, many of the studies rely on self-reported data which is notoriously unreliable. People tend to quickly forget the details of what they ate at any particular day and time. Deliberate omission of foods perceived as “bad” also occurs. Modifications such as these can lead to large errors in data. In fact, the acknowledged effects of saturated fats on cholesterol levels and the consequent effects of cholesterol on cardiovascular disease were largely ignored in these two meta-analyses (15,17). To sum this up, what these studies actually showed is that when people remove saturated fat from their diet and replace those calories with refined carbohydrates and sugar there is no health advantage at all. What they definitely did not find is that butter, meat and cheese belong in a healthy diet.
The conclusions drawn from these two meta-analyses were refuted immediately by numerous highly respected health organizations and authors based on the poor quality of the research (9,10,11,13,14,15,16,17,41). In the aftermath, Dariush Mozaffarian, one of the scientists involved in the 2010 meta-analysis, pointed out that its actual finding was not that saturated fat is a healthy food. He stated, “Overall, our results suggest that butter should neither be demonized nor considered “back” as a route to good health. More data is needed” (6,8). It is also interesting to note that Patty Siri-Tarino, lead researcher of the 2010 meta-analysis, is now promoting a diet modest in fat and based on vegetables, nuts, whole grains and fish (18,12).
Where does cholesterol fit in?
There is no question that saturated fat increases cholesterol (19). Proving that cholesterol increases cardiovascular disease has been a little more difficult. However, recently and without any media fanfare, another important meta-analysis was published. The European Atherosclerosis Society completed an astoundingly extensive review of current clinical and genetic evidence regarding the association between LDL cholesterol and atherosclerotic cardiovascular disease. This comprehensive analysis included over 200 different studies including controlled, randomized trials along with prospective cohort studies, genetic studies and Mendelian randomization studies encompassing more than 2 million participants with over 20 million person-years of follow-up. Their conclusion is as follows; “Consistent evidence from numerous and multiple different types of clinical and genetic studies unequivocally establishes that LDL causes atherosclerotic cardiovascular disease.” (39).
Studies…controlled, randomized, blind, epidemiological, observational, cohort….
The gold standard of scientific study is a controlled, randomized trial that includes a placebo group for comparison. In other words, one defined group of people would be required to eat saturated fat while another group of people would eat no saturated fat and this would have to be carried out in such a manner that the subjects involved would not know which group they were in. Then both groups would need to be monitored over many years to identify the development of cardiovascular disease. It is obvious that this process poses many difficulties, not the least of which is keeping people in a controlled environment over a long term. There is a growing realization that the controlled, randomized trial is not perfect and that many questions simply cannot be studied using this approach (40). Accordingly, epidemiological or observational population studies (also called prospective cohort studies) are used in which subjects initially free of disease are classified according to exposure to a risk factor and followed over time to determine the incidence of an outcome. Observational studies show an “association” as opposed to a “cause”.
Thousands of observational studies over many decades have definitively shown the association between cholesterol levels and cardiovascular disease (17,20,21,22,23,24,25,26). One or two observational studies do not hold much weight but decades of studies repeating the same connections cannot be ignored. For example, Finland undertook a community-based study designed to reduce the extremely high levels of cardiovascular disease risk factors in the population of the eastern Finnish province of North Karelia. Education led to widespread reduction in saturated fat intake along with an increase in the consumption of fruits and vegetables over the course of 25 years and resulted in a significant decline in the risk factors for cardiovascular disease, an 85% drop in death from coronary heart disease and a general ten year increase in life expectancy (20). The Cochrane Group is a global independent network of researchers who are free from commercial sponsorship and other conflicts of interest. Their work is recognized as the international gold-standard for high quality, trusted information. In 2015 the Cochrane Group reviewed fifteen studies with over 59,000 participants and found that cutting down on saturated fat leads to a 17% reduction in the risk of cardiovascular disease (including heart disease and stroke) (35). The National Academy of Sciences states that any intake of saturated fat above zero increases “bad” LDL cholesterol (29). The American Heart Association recommends keeping saturated fat to a maximum of 5 to 6% of total calories (27). The Canadian Heart and Stroke Foundation suggests limiting saturated fats to as little as possible (30). Eat Right Ontario recommends that saturated fat should be limited to no more than 10 % of your daily calorie intake (28). A whole food, plant-based diet averages approximately 6% to 7% of calories from saturated fat (42). It is surprising to consider that eating only two slices of cheese could provide you with more than the recommended daily amount of saturated fats.
Fat and health
There is no single cause for heart disease. We do know, however, that every food decisively associated with reduced risk of chronic diseases (including heart disease, cancer, diabetes and many others) and premature death from all causes is low in saturated fat. These foods are also low in added sugar and refined carbohydrates. All of the diets associated with longevity and vitality are low in saturated fat, added sugar and refined carbohydrates. Despite the controversy amongst members of the population surrounding their food choices, the Ornish Program for Reversing Heart Disease has proven its efficacy to the CMS (Centers for Medicare and Medicaid Services) and has been covered under Medicare and by many other commercial payers in the United States since 2010 (36,37,38). The Ornish Program centers around a whole-food plant-based diet that is completely free of all animal based foods along with moderate exercise and stress management. People in Blue Zones eat a diet extremely low in saturated fat. Blue Zones are populations of defined areas around the world who live an exceptionally long life and have extremely low rates of heart disease, stroke, cancer, osteoporosis, Alzheimer’s and dementia.
Food must be looked at as a package deal, not as a mixture of many separate nutrients. We do not eat “saturated fat”. We eat meat and dairy. We eat fruits and vegetables. It is becoming increasingly apparent that part of the problem with saturated fats may be the company they keep. Foods high in saturated fats are also high in total fat, animal protein and heme iron which are all independently associated with higher risk of cardiovascular disease as well as cancer and diabetes (31,32,33,34). Eating substantial amounts of foods that contain saturated fat leaves less room in your stomach for more health-giving foods with their beneficial nutrients, fiber and antioxidants. Surely cutting back on saturated fats makes more sense than treating them as healthy foods.
Stay tuned for Part Two of this article which resolves the confusion in a clear and substantive look at the evidence for the relationship between saturated fat and cardiovascular disease.
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38 Tuso, P.H., Ismail, M.H., Ha, B.P. and Bartolotto, C. Nutritional Update for Physicians: Plant-Based Diets. Perm J. 2013 Spring; 17(2): 61-66.
39 Ference, B.A., Ginsberg, H.N., Graham, I. et al. Low-density lipoproteins cause atherosclerotic cardiovascular disease. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. Eur Heart J April 4, 2017.
40 At Work, Issue 83, Winter 2016: Institute for Work & Health, Toronto