In a “presidential advisory” to the American Heart Association (AHA) a panel of experts last week strongly endorsed the heart healthy benefits of replacing any and all saturated fats in our diet with vegetable oils (like corn , soy, and canola oil) which contain predominantly poly or mono unsaturated fats.
Examining the metrics of this article it appears that the vast majority of news media reporting on it have lead with a headline that reads:
Given this brazen attempt by the AHA to smear coconut oil’s reputation I felt compelled to revisit my analysis of coconut oil from a year ago. I’ve included new discussion on a key paper referenced by the AHA advisory and some words of wisdom from Gary Taubes.
Coconut Oil: Poster Child for Dietary Fat Confusion
Coconut oil (CO) is a microcosm of the dietary confusion present in the U.S. On one hand a CO Google search yields a plethora of glowing testimonials to diverse benefits: Wellness Mama lists “101 Uses for Coconut Oil,” Authority Nutrition lists “10 Proven Health Benefits.”
On the other hand, the American Heart Association (AHA) and the USDA’s Dietary Guidelines For Americans warn us to avoid consuming coconut oil because it contains about 90% saturated fat (SFA) which is a higher percentage than butter (about 64% saturated fat), beef fat (40%), or even lard (also 40%)
In many respects, the vilification of coconut oil by federal dietary guidelines and the AHA resembles the inappropriate attack on dairy fat and is emblematic of the whole misguided war on dietary fat. In fact, the new AHA advisory after singling out coconut oil goes on to cherry-pick the data on dairy fat and cardiovascular disease in order to support their faulty recommendations for choosing low or nonfat dairy..
The AHAs simple message to replace all saturated fats in your diet with poly unsaturated fats (PUFAs) or monounsaturated fats (MUFAs) is flawed because:
All saturated fats are not created equal :the kinds of saturated fats in coconut oil differs markedly from both dairy SFAs and beef SFAs . Some SFAs may have beneficial effects on blood lipids, weight, and cardiovascular health.
- The types of nonSFAs in vegetable oils differ markedly and may have differential effects on cardiovascular health.
All Saturated Fats Are Not Created Equal!
Saturated fats are divided into various types based on the number of carbon atoms in the molecule. Depending on length, they differ markedly in their metabolism, absorption and effects on lipid profiles.
The major SFA in coconut oil, lauric acid, has a 12 carbon chain and is thus considered a medium chain fatty acid (MCFA).
The Mensink meta-regression analysis determined the effects on blood lipids of replacing carbohydrates with the individual saturated fatty acids that are in common foods, including lauric, myristic, palmitic, and stearic ac- ids. Lauric, myristic, and palmitic acids all had similar effects in increasing LDL cholesterol and HDL cholesterol and decreasing triglycerides when replacing carbohydrates
In summary, the common individual saturated fats raise LDL cholesterol. Their replacement with monounsaturated or polyunsaturated fats lowers LDL cholesterol. Differences in the effects of the individual fatty acids are small and should not affect dietary recommendations to lower saturated fat intake.
But if we examine what the actual paper by Mensink et al (available in full here) we find their conclusions are the exact opposite of the AHA:
Lauric acid greatly increased total cholesterol, but much of its effect was on HDL cholesterol. Consequently, oils rich in lauric acid decreased the ratio of total to HDL cholesterol. Myristic and palmitic acids had little effect on the ratio, and stearic acid reduced the ratio slightly.
The differences in the effects of the individual fatty acids are not small they are quite significant if we look at the totality of the effects on lipids relevant to cardiovascular disease. In their discussion, Mensink, et al go on to say:
Our results emphasize the risk of relying on cholesterol alone as a marker of CAD risk. Replacement of carbohydrates with tropical oils markedly raises total cholesterol, which is unfavorable, but the picture changes if effects on HDL and apo B are taken into account.
What’s more :
The picture may change again once we know how to interpret the effects of diet on postprandial lipemia, thrombogenic factors, and other, newer markers. However, as long as information directly linking the consumption of certain fats and oils with CAD is lacking, we can never be sure what such fats and oils do to CAD risk.
This graph from Mensink, et al. shows what would happen to the total/HDL cholesterol ratio if we substituted various foods in place of 10% mixed fat. Theoretically a lower ratio is more heart healthy. Look at the drastic differences between palm oil, coconut oil and butter, all of which are condemned by the AHA
Misguided Dietary Fat Recommendations
The AHA experts have doubled down on their recommendation to use cooking oils that have less saturated fat such as canola and corn oil. They advise, in general, to “choose oils with less than 4 grams of saturated fat per tablespoon.”
Canola and corn oil, the products of extensive factory processing techniques, contain mostly mono or polyunsaturated fats which have been deemed “heart-healthy” on the flimsiest of evidence.
The most recent data we have on replacing saturated fat in the diet with polyunsaturated fat comes from the Minnesota Coronary Experiment performed from 1968 to 1973, but published in 2016 in the BMJ.
Data from this study, which substituted liquid corn oil in place of the usual hospital cooking fats, and corn oil margarine in place of butter and added corn oil to numerous food items, showed no overall benefit in reducing mortality. In fact, individuals over age 65 were more likely to die from cardiovascular disease if they got the corn oil diet.
The new AHA presidential advisory doesn’t include this study or data from the Sydney Heart Study, another study with negative results for substituting PUFAs for SFAs.
As Gary Taubes pointed out in a post for Larry Husten’s cardiobrief.org blog, the AHA experts cherry-picked four “core trials” that agreed with their hypothesis and excluded the ones that don’t agree:
They do this for every trial but the four, including among the rejections the largest trials ever done: the Minnesota Coronary Survey, the Sydney Heart Study, and, most notably, the Women’s Health Initiative, which was the single largest and most expensive clinical trial ever done. All of these resulted in evidence that refuted the hypothesis. All are rejected from the analysis. And the AHA experts have good reasons for all of these decisions, but when other organizations – most notably the Cochrane Collaboration – did this exercise correctly, deciding on a strict methodology in advance that would determine which studies to use and which not, without knowing the results, these trials were typically included.
Coconut Oil: The Bottom Line
After all is said and done, it would appear that coconut oil, despite coming from a vegetable, resembles dairy fat in many ways.
It is more likely than not that coconut oil, like dairy fat, reduces your chances of obesity and heart disease, especially when compared to the typical American diet of highly processed and high carbohydrate foods.
Although containing lots of saturated fat, the SFAs in coconut oil are drastically different from other dietary sources of SFA. The medium chain fatty acids like lauric acid which make up the coconut are absorbed and metabolized differently from long chain fatty acids found in animal fat.
The only explanation for dietary guidelines advising against coconut oil and dairy fat is the need to stay “on message” and simplify food choices for consumers, thus continuing the vilification of all saturated fats.
Substituting corn oil (or other vegetable oils with lots of linoleic acid) for foods containing saturated fats does not lower risk of heart disease and may promote atherosclerotic outcomes like heart attack and stroke.
Finally, I agree with Taubes that we deserve good scientific studies proving without a doubt that these drastic changes in diet are truly helping:
“telling people to eat something new to the environment — an unnatural factor, à la virtually any vegetable oil (other than olive oil if your ancestor happen to come from the Mediterranean or mid-East), …..is an entirely different proposition. Now you’re assuming that this unnatural factor is protective, just like we assume a drug can be protective say by lowering our blood pressure or cholesterol. And so the situation is little different than it would be if these AHA authorities were concluding that we should all take statins prophylactically or beta blockers. The point is that no one would ever accept such a proposal for a drug without large-scale clinical trials demonstrating that the benefits far outweigh the risks. So even if the AHA hypothesis is as reasonable and compelling as the AHA authors clearly believe it is, it has to be tested. They are literally saying (not figuratively, literally) that vegetable oils — soy, canola, etc — are as beneficial as statins and so we should all consume them. Maybe so, but before we do (or at least before I do), they have a moral and ethical obligation to rigorously test that hypothesis, just as they would if they were advising us all to take a drug.”
For those seeking more information.
This graph is from the BMJ paper which also included a meta-analysis of all randomized studies substituting linoleic acid for saturated fat. The data do not favor substituting corn oil for saturated fat