On 15 June 2017, the American Heart Association released a “presidential position statement” published in the journal Circulation which, in part, said:
This American Heart Association presidential advisory on dietary fats and [cardiovascular disease, CVD] reviews and discusses the scientific evidence, including the most recent studies, on the effects of dietary saturated fat intake and its replacement by other types of fats and carbohydrates on CVD.
In summary, randomized controlled trials that lowered intake of dietary saturated fat and replaced it with polyunsaturated vegetable oil reduced CVD by ≈30%, similar to the reduction achieved by statin treatment.
Because coconut oil contains more saturated fat relative to other cooking oils, people personally or financially invested in those products seem to have taken this statement as a slight, going aggressively on the defensive. One response to the report that has frequently graced our inbox (and which has been reproduced on countless other websites) comes from a website named Sustainable Dish, which argued that the nonprofit American Heart Association cannot be trusted because of its ties to corporate America.
In an article (“Why Coconut Oil Won’t Kill You, But Listening to the American Heart Association Might!”) that appears on a web site selling coconut oil and which receives a commission on the coconut oil-based diet books that appear on the page, Sustainable Dish argues that the AHA is an organization corrupted by corporate interests which cherrypicks data to support the results it wants in order to fund its nefarious non-profit operations:
You may have seen the news late last week about the latest “Presidential Advisory” on dietary fats released from the American Heart Association (AHA) published online in Circulation. The part of this report that seems to be making the most news around the internet is that coconut oil is unhealthy.
In the last few days I’ve seen titles like “Coconut Oil is as Bad as Butter”, “Coconut Oil is Unhealthy and Has Never Been Healthy”. Not only do these types of headlines cause increased confusion for the general population, for those of us who understand the nuances and politics behind the AHA’s statement it’s absolutely infuriating. […]
In recent years, there have been 17 meta-analyses and systematic reviews conducted that have not found a clear link between saturated fat intake and heart disease. Of those that reviewed clinical trials on the subject, (instead of just epidemiological studies) not one found any connection between saturated fat intake, heart disease, and mortality.
We do not seek to weigh in on the debate over whether coconut oil is “healthy” or “clean”, as these terms imply that foods exist on a binary of “bad” and “good” that does a disservice to actual science.
Instead, this post seeks to separate fact from fiction in posts purporting to attack the scientific rationale provided by the American Heart Association. The dichotomy presented by Sustainable Dish is a false one, and in many cases the post misrepresents published scientific work that they use to support their argument.
The American Heart Association Argument
The Sustainable Dish post presents the argument as a choice between a large body of independent research that does not demonstrate a connection between saturated fat and heart disease on one side, and four cherrypicked studies on the other. This false dichotomy deliberately omits, essentially, the meat of the scientific debate over saturated fat research in the first place. The debate is over what kind of study can be used to address that question.
Broadly speaking, meta-reviews like the one conducted by the AHA have demonstrated clinical trials in which saturated fat is replaced with another, unsaturated fat, show a reduced risk of heart disease, while studies that replace saturated fat with something else, like carbs, do not. The AHA argues that studies in which fats are replaced with non-fats or which were not rigorously controlled, are a poor experimental design to test the question of whether or not reducing saturated fat reduces risk of heart disease:
Because carbohydrates and unsaturated fats differ in their metabolic effects, it is necessary to evaluate the effects of low and high saturated fat intakes in the context of the replacement macronutrient. This is easier in a clinical trial because the trial controls the dietary intake but more complicated in observational studies in which the participants control their own diets.
That kind of study is fundamentally different from another type of study used to address this question — prospective observational studies (or cohort studies), in which large populations of people have their dietary intake recorded and their health assessed regularly. Importantly, these studies do not control the diets of the participants.
The AHA makes the argument that this question is best addressed in a case-controlled, clinical trial in which saturated fat is replaced by unsaturated non-trans fats. They added an additional requirement that that the studies last at least two years (evidence suggests that it takes at least two years for changes in dietary fats to affect tissue), rejecting the inclusion of observational studies entirely:
These trials compared high saturated with high polyunsaturated fat intake; did not include trans unsaturated fat as a major component; controlled the dietary intake of the intervention and control groups; had at least 2 years of sustained intake of the assigned diets; proved adherence by objective biomarkers such as serum cholesterol or blood or tissue levels of polyunsaturated fatty acids; and collected and validated information on cardiovascular or coronary dis- ease events.
An analysis of the trails that fit this criteria led the AHA to the following conclusion:
Randomized controlled trials that lowered intake of dietary saturated fat and replaced it with polyunsaturated vegetable oil reduced [cardiovascular disease] by ≈30%, similar to the reduction achieved by statin treatment.
One can legitimately debate the AHA on the merits of this approach, but to suggest that it stems from cherrypicking (in which data is selected to provide a predetermined conclusion) misleadingly omits the main scientific controversy that generated it. Any response must make a rational counterargument for why the studies they point to are superior to the ones the AHA used. They also must accurately describe the studies they cite.
The “Sustainable Dish” Argument
The heart of the claim against the AHA statement presented by Sustainable Dish is that “there have been 17 meta-analyses and systematic reviews conducted that have not found a clear link between saturated fat intake and heart disease” and that “of those that reviewed clinical trials on the subject, (instead of just epidemiological studies) not one found any connection between saturated fat intake, heart disease, and mortality”.
Both of those statements are demonstrably false; one need only read the actual studies they cite to prove that point. The information allegedly (and solely) comes from a post (which also says “Note: This page needs updating”) on a “Nutrition Coalition” site that lists sixteen recent studies (we remain unclear where number 17 went) on saturated fat and heart disease. Four of the studies, including the very first one listed, counter to the Sustainable Dish claims, state directly that meta-analyses of controlled clinical trials that investigate the reduction of saturated fat demonstrate reduction in heart disease:
OBJECTIVES: To assess the effect of reducing saturated fat intake and replacing it with carbohydrate, polyunsaturated or monounsaturated fat and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.
AUTHORS CONCLUSIONS: The findings of this updated review are suggestive of a small but potentially important reduction in cardiovascular risk on reduction of saturated fat intake.
OBJECTIVES: To assess the effect of reduction and/or modification of dietary fats on mortality, cardiovascular mortality, cardiovascular morbidity and individual outcomes including myocardial infarction, stroke and cancer diagnoses in randomised clinical trials of at least 6 months duration.
AUTHORS’ CONCLUSIONS: The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.
CONCLUSIONS: These findings provide evidence that consuming [polyunsaturated fat] in place of [saturated fat] reduces CHD events in [randomized controlled trials].
In summary, although substitution of dietary polyunsaturated fat for saturated fat has been shown to lower CVD risk, there are few epidemiologic or clinical trial data to support a benefit of replacing saturated fat with carbohydrate [which is a different question].
Further, to represent this list of sixteen studies as “17 meta-analyses and systematic reviews”, (the latter in particular of which is a technical term that comes with methodological requirements) is to ignore the fact that many of the studies were, in fact, informal commentaries and neither meta-analyses nor systematic reviews (Ravnskov et al 2014, Thornley et al 2014, Lawrence 2013).
Therefore, the only two direct scientific critiques of the AHA position statement made on the Sustainable Dish website (and those websites that aggregate the post) are false, and betray a lack of interest in the actual science they claim is being misrepresented.
To be sure, many of the studies on the list do not show any evidence that reducing saturated fat in one’s diet reduces one’s risk of heart disease. Those studies all make use of observational designs or clinical trials that do not replace the saturated fat with another fat (at least in part), which — as the AHA themselves acknowledges in their position statement — have not generally shown any benefit to heart health from reducing saturated fat.
A more effective, or at least honest, response to the AHA position statement would be a defense of using observational studies and/or studies that replaced saturated fat with things other than a fat. Instead, Sustainable Dish fails to acknowledge the fact that these methodological debates (which are real and ongoing) are the basis for AHA’s data selection in the first place.