Disrobing Dogma – Saturated Fat: The Heart Of The Matter

The first installment in Disrobing Dogma laid to rest the claim that isocaloric, low-carbohydrate diets are quantitatively superior for fat loss. This time another sorry piece of dogma is buried, that saturated fat causes heart disease.

Origins Of Indictment

In 1953, Ancel Keys conducted an ecological study documenting 9 countries and their respective saturated fat intake. He found a strong, almost unmistakable curvilinear correlation between heart disease and fat consumption [1]. Although the veracity of these findings were later called into question [2], Keys became instrumental in his position and went on to develop the diet-heart hypothesis, which states that i) dietary saturated fat raises blood cholesterol and ii) raised blood cholesterol causes heart disease; iii) ergo, saturated fat causes heart disease. This idea was uncritically adopted by medical authorities and governmental institutions during the ’60s when heart disease was making its inexorable stampede across the civilized world. Almost half a century later, regrettably, nothing has changed.

Location of the heart in the human body

The diet-heart hypothesis features several shortcoming in all its assertions. Indeed, the first [3,4] and second [5] postulates have been critiqued at length, however the most voluminous and compelling evidence comes from the prodigious body of evidence investigating the direct relationship between saturated fat and heart disease, both observational and experimental in nature.

Starting with the observational evidence, in 2009, Skeaff and Miller published a meta-analysis of cohort studies that provided data on saturated fat intake and coronary heart disease (CHD) finding no significant association [6]. A much more extensive meta-analysis by Siri-Tarino et al. corrobrated these results in 2010 [7]. In a pooled analysis of 21 studies, including some 350,000 subjects with 11000 cases, they again found no evidence for a significant association between saturated fat consumption and coronary heart disease (CHD) or cardiovascular disease (CVD). In my own review of the literature, I found an additional 9 studies that met the inclusion criteria of the meta-analysis [8,9,10,11,12,13,14,15,16,17]. Of these, only one study found an association, however the difference in absolute saturated fat intake between CHD and CHD-free individuals in this study was not clinically meaningful at only 5 grams more per day  [17].

Although case-control studies carry less weight than a prospective cohort study, they are still worth examining. In a meticulous sweep of the literature I found 7 case-control studies, none of them show any significant association either [18,19,20,21,22,23,24].

Loads of saturated fats: truly responsible for heart disease?

It’s been established that the observational evidence incriminating dietary saturated fat for the past 5 decades has been largely, if not totally unfounded. Unfortunately, on the basis of observational evidence it is unequivocally impossible to establish cause and effect relationships between variables in diet, lifestyle and disease. To ascertain causation, the best hope is the controlled trial. Fortunately, several trials have been performed over the years investigating saturated fat and heart disease, do they offer support for the diet-heart hypothesis?

Saturated Fat On Trial

Controlled trials are the gold-standard of experimental science. They are expensive, time-consuming and definitely much more difficult to control and conduct than the conventional observational study. Controlled trials can prove causality because variables have been manipulated.

It becomes quickly obvious that most trials have been a woeful failure. If saturated fat was the demonic plague on modern society as so readily portrayed by health authorities, this would have been clearly reproducible in controlled trials. But sadly, it hasn’t. Substituting saturated fat with polyunsaturated fat has never been convincingly proven to lower mortality. A meta-analysis of these same trials was published in late-2010 also reached these conclusions [38].

Practical Implications

Establishing now that saturated fat is not the deleterious ‘heart-disease-causing-monster’ it’s so often characterized as, what are the real-life consequences of such information? It is simple. Trimming your meats with surgical precision is no longer required, enjoy the fats. These fattier portions also contain the highest concentrations of fat-soluble vitamins including the all important, A, D and E [39]. Don’t shy away from cooking with butter and coconut oil, saturated fatty acids are devoid of double-bonds, thus making them the most chemically stable fat when heated. On the contrary, heated vegetable oils have been shown numerous times to increase the activity of free-radicals in both animal and human models [40,41,42,43,44,45,46,47].

Conclusions

Research spanning close to half a century on saturated fat and heart disease has produced innumerable scientific papers. Astonishingly, at least 35 cohort and case-control studies have found no association between saturated fat consumption and heart disease. Even the more qualitatively superior controlled trials have failed to show any reductions in mortality from restricting dietary saturated fat.

The oversimplistic and fundamentally incorrect idea that saturated fat raises blood cholesterol and thus causes heart disease should have been forsaken decades ago. It is totally unreasonable to promulgate recommendations to restrict a particular dietary constituent by the changes on a single biomarker. After assessing the amassed literature, there is no scientific reason why any individual should subscribe the current international recommendations to eschew saturated fat rich foods, these often also being nutrient-dense foods such as egg-yolks and fatty cuts of meat. Enjoy the fat, just as nature intended.

Pictures courtesy of Jules Morgan, Mikael Häggström and Robert Young.