On 2017 Aug 06, Stuart Buck commented:

What bothers me most is the following statement from a study author: "Each of these increase LDL-cholesterol compared to carbohydrate and more so when compared to the unsaturated fats. This is sufficient to warn the public about anticipated adverse effects of coconut oil on CVD."

No, it is not. There are at least 5 treatments that lower LDL without lowering CVD, and sometimes even make CVD worse. See Table 1: http://www.nejm.org/doi/full/10.1056/NEJMp1508120?af=R&rss=currentIssue#t=article.

Nutritionists should not give advice based on trials about LDL while ignoring that LDL manipulation is often disconnected from or even directly contrary to CVD outcomes.

On date unavailable, commented:

None

On 2017 Aug 02, Hilda Bastian commented:

Thank you for the reply, Professor Sacks. However, the reply does not address the errors I pointed to, nor respond directly the key problems I raised. Much of it is directed to rebutting claims I did not make.

... (1) Lack of reporting on the processes for selecting evidence

My first point was that although the statement asserts that the totality of evidence and recent studies was reviewed, it does not report the process for identifying the systematic reviews it selected. No validated method for evaluating the systematic reviews is reported, and reasons for excluding each of the trials in the chosen systematic reviews are not reported either (with the exception of 6 trials, accounting for 10 trials in total). Hamley S, 2017, for example, lists 19 randomized trials on the question of replacing saturated with polyunsaturated fat, drawn from 8 systematic reviews/meta-analyses (Table 2). I stress that my point here is not related to the conclusions, but rather to the adequacy and transparency of the methodology.

The totality of evidence approach considering a variety of research types does not obviate the need to explain how the studies were sought, selected, and appraised (Institute of Medicine (US) Committee on Standards for Developing Trustworthy Clinical Practice Guidelines, 2011).

... (2) Singling out coconut oil

The reply reiterates a statement based on a single survey and people's beliefs about coconut oil. But there is no data to show that dietary coconut oil is consumed at levels that warrant this attention, whereas palm oil, for example, does not. I am not sure whether the data I could find on this is an accurate reflection or not (Bastian, June 2017). If it is, however, then the issue of replacing palm oil in commercially produced food would have warranted more attention than coconut oil. Given the very different standards applied to studies of coconut oil, the question of why it was addressed at all, when so much else in scope was not, remains a relevant one.

... (3) Inadequacy of Eyres L, 2016 as a basis for wide-ranging conclusions on health effects of coconut oil

I reiterate the point I made: the conclusions that clinical trials on the effects on CVD measures have not been reported, and that there are "no known offsetting favorable effects" would require a high-quality systematic review on the effects of coconut oil on both CVD and non-CVD health outcomes of dietary coconut oil. Eyres L, 2016 is not that review. Whichever of the validated and accepted methodologies for assessing the quality of a systematic review you would use (Pussegoda K, 2017), the Eyres review would not fare well. It does not include elements required for a high quality systematic review - such as reporting on the excluded studies and including a study-by-study assessment of the methodological characteristics and risk of bias of included studies. More importantly, its scope is too narrow.

I identified the 8 trials in the 7 papers I mention, in a quick search to test the adequacy of coverage of the Eyres review. I only included those on CVD outcomes. There are undoubtedly further relevant trials. That short search though, established the limits of scope of the Eyres review, even in CVD health.

This is how the authors of the Eyres characterize the evidence they found:

"Much of the research has important limitations that warrant caution when interpreting results, such as small sample size, biased samples, inadequate dietary assessment, and a strong likelihood of confounding. There is no robust evidence on disease outcomes, and most of the evidence is related to lipid profiles."

I agree with that assessment, and the reply offers no methodologically sound counter to this. Instead, the studies not in the Eyres review were critiqued. The reply cites these criteria for excluding all but 3 of the 8 studies as acceptable for consideration (presumably the 2 reported in a single paper were regarded as a single study):

[A]mong the 7 studies...4 would appropriately be excluded as result of being non-randomized, uncontrolled, using a very small amount, not including a control group or not even being a trial of coconut oil.

I don't really know what to make of "uncontrolled" and "not including a control group" as 2 criteria, given all these trials are controlled: the final 3 that aren't rejected don't make it clear to me either. No threshold is offered for what is a large enough dose, so I can't work with that either. However, I took the other 2 - randomized or not, and having a solely coconut oil arm as objective criteria I could apply to the 8 trials within Eyres and the 8 trials outside it (and extracted some additional data). This is reported in full on a blog post (Bastian, August 2017). In summary:

• The Eyres group has fewer randomized trials: 4/8 compared to 7/8 in the non-Eyres group (or 6/7 for non-Eyres after knocking out the trial with no separate coconut arm).
• There are fewer randomized participants in the Eyres group: 143 compared to 234 in 6 non-Eyres randomized trials with a separate coconut arm.
• All the trials in the Eyres group only look at blood lipid profiles whereas most in the non-Eyres group assess at least 1 non-blood-test outcome (5/8 or 4/7). That is in part because of the Eyres exclusion criteria (such as rejecting any trial in a specific population or clinical subgroup, such as overweight people).

The Eyres group cannot be regarded as an adequate or representative subset of trials. And the same level of critique has not been applied even-handedly.

... (4) Errors in representation of the Eyres findings on coconut oil versus other saturated fats

As this was not addressed in the reply, I'll reiterate it, with additional detail. This is what the Eyres review concludes on this question:

"In comparison with other fat sources, coconut oil did not raise total or LDL cholesterol to the same extent as butter in one of the studies by Cox et al., but it did increase both measures to a greater extent than did cis unsaturated vegetable oils...[W]hen the data from the 5 trials that directly compared coconut oil with another saturated fat are examined collectively, the results are largely inconsistent".

This is what the AHA writes:

"The authors also noted that the 7 trials did not find a difference in raising LDL cholesterol between coconut oil and other oils high in saturated fat such as butter, beef fat, or palm oil".

As there was no meta-analysis of these trials, there is no single estimate to discuss. Of the 5 that did include a comparison with saturated fats, there were differences among their results: the AHA had pointed out 1 of them just a few sentences previous to their "no difference" statement. This is objectively a mis-statement of the Eyres' review's findings, which results in an exaggeration of the strength of the evidence.

Nothing in the reply to my comment changes, for me, the conclusion I came to in my first blog post on this:

"On coconut oil, the AHA has taken a stand on very shaky ground with some major claims – as though they had a very strong systematic review of reliable research on all possible health consequences of dietary coconut oil. They don’t. The people arguing the opposite – that coconut oil is so healthy you should try to use it every day – are also on shaky ground".

Disclosure: I have no financial, livelihood, or intellectual conflicts of interest in relation to coconut or dietary fats. I discuss my personal, social, and professional biases in a blog post that discusses the AHA advisory on coconut oil in detail. (Bastian, August 2017). This PubMed Commons comment also contains some excerpts from that post.

On 2017 Jul 24, Frank M Sacks commented:

On behalf of the authors, I respond to comments by Hilda Bastian about the American Heart Association Presidential Advisory on Dietary Fats and Cardiovascular disease Sacks FM, 2017.

The comprehensive advisory includes, (i) Clinical trials that tested the effects of dietary saturated fat compared to unsaturated fat or carbohydrate on cardiovascular disease (CVD) events, e.g. heart attack, (ii) Clinical trials that tested the effects of dietary fats on lipid risk factors, e.g. LDL-cholesterol, (iii) Prospective epidemiological studies on dietary fats and carbohydrates and CVD, and (iv) Animal models of diet and atherosclerosis. Thus, it reflects the “totality of evidence”. The confluence of findings provides a very strong scientific case for the recommendation that dietary saturated fat be replaced with unsaturated fat, especially polyunsaturated fat.

Recent systematic reviews and meta-analyses Mozaffarian D, 2010, Chowdhury R, 2014, Hooper <PMID: 26068959 used well accepted methodologies, and included trials published up to 2009, 2013, and 2014. Only a small number of clinical trials evaluated direct effects of dietary fat on CVD. Most of these studies, and all that have an impact on the overall findings, were conducted years ago, and are well known. Contrary to the Bastian’s comments, there are no more recent trials on this topic. These 3 meta-analyses each confirm the beneficial effect of replacing saturated with polyunsaturated fat. The similarity of findings lends robustness to the overall conclusions of the report. The meta-analyses and all the individual trials are discussed critically in detail in the advisory.

Because the topic of the advisory is the effect of dietary fats on CVD, coconut oil is well within its scope. Coconut oil is currently rated as a healthy oil by 72% of the American public, despite its composition derived from 98% saturated fats, which increase the blood level of LDL-cholesterol, a cause of atherosclerosis and CVD. The meta-analysis by Mensink reports the quantitative effects on LDL-cholesterol of the saturated fats that are in coconut oil, mainly lauric, myristic, and palmitic acids. Each of these increase LDL-cholesterol compared to carbohydrate and more so when compared to the unsaturated fats. This is sufficient to warn the public about anticipated adverse effects of coconut oil on CVD.

Some studies tested coconut oil itself, and found that it increases LDL-cholesterol as would be predicted by its saturated fat content. These studies were identified and summarized in the systematic review by Eyres L, 2016 which used rigorous, well-accepted methodology. The criteria for inclusion of an article in the systematic review were well conceived. Eyres et al. concluded, “Overall, the weight of the evidence from intervention studies to date suggests that replacing coconut oil with cis unsaturated fats would alter blood lipid profiles in a manner consistent with a reduction in risk factors for cardiovascular disease.” Bastian implies that this systematic review is composed of weak studies and omitted several studies that would affect the conclusion of the advisory to avoid eating coconut oil. This is not true. Eyres et al. identified eight studies; all were controlled clinical trials that used valid nutritional protocols and statistical analyses. All reported higher LDL-C levels when coconut oil was consumed compared to unsaturated oils, including olive, corn and soybean oils, statistically significantly in 7 of them. Together, these trials included populations from the US, Sri Lanka, New Zealand, Pacific Islands, and Malaysia, demonstrating generalizability. There is no objective scientific reason to disparage them. The only substantive criticisms mentioned by Bastian are a short duration and small sample. These criticisms are unwarranted. Effects of diet on blood lipids, especially LDL-cholesterol, are established quickly, by 2 weeks. A small sample, with careful dietary control and execution, can yield a well-powered trial with valid results. In summary, the 8 trials in the Eyres et al. systematic review provide strong evidence that coconut oil increases LDL-C levels compared with unsaturated oils.

What about the 7 studies named by Bastian that were not included in the systematic review? McKenney JM, 1995 reported that coconut oil increased LDL-cholesterol significantly by 12% compared with canola oil in 11 patients with hypercholesterolemia. In a second study in 17 patients treated with lovastatin, LDL-C increased nonsignificantly in the coconut oil period. Thus, the results of this small study would add to the overall effects of coconut oil shown in the other studies to increase LDL-cholesterol. Ganji V, 1996 reported that coconut oil increased LDL-cholesterol compared to soybean oil in 10 normal participants. Assunção ML, 2009 reported no difference in the effects of coconut and soybean oils on LDL-cholesterol levels. However, LDL-cholesterol levels increased during the soybean oil period, clearly an anomolous result. Cardoso DA, 2015 conducted a nonrandomized study comparing coconut oil, 13 mL per day, with no supplemental oil. Because there is no control for the coconut oil, it is unclear how to interpret the lack of difference in LDL-cholesterol between the groups. de Paula Franco E, 2015 conducted a sequential study of a calorie-reduced diet followed by coconut flour, 26 g per day. This study was not randomized and did not have a control group. Enns reported in her Ph.D. degree dissertation at the University of Manitoba the results of a randomized trial that compared a 2:1:1 mix of butter, coconut oil, and high-linoleic safflower oil, 25 g per day, with canola oil, 25 g per day. This trial did not claim to be a study on the effects of coconut oil. Finally, Shedden reported in her M.S. degree thesis at Arizona State University the results of a placebo-controlled randomized trial of coconut oil, 2 g per day. This miniscule amount of coconut oil did not affect LDL-cholesterol. In summary, among the 7 studies cited by Bastian not in the Eyers review, 4 would appropriately be excluded as result of being non-randomized, uncontrolled, using a very small amount, not including a control group or not even being a trial of coconut oil. Among the 3 randomized trials, McKenney et al., Ganji et al. and Assuncao et al., the first two found that coconut oil increased LDL-cholesterol levels. The trial of Assuncao et al. would likely fail an outlier test because it is the only one among 12 studies in which LDL-C levels is lower on coconut than soybean oil. Given the differences in study designs, populations, and localities, the results of coconut oil trials are remarkably uniform showing that it increases LDL-cholesterol levels, an established cause of cardiovascular disease.

Bastian employs a tactic in common with some other critics of good nutritional science, namely, to a) disparage and misrepresent high quality studies that show harmful effects of saturated fat; b) promote and misrepresent seriously flawed and irrelevant studies that report the opposite; and c) cite meta-analyses with faulty designs often based on inclusion of flawed studies. We offer a challenge to those who assert health benefits to coconut oil, or saturated fat, in general. Produce well-designed and executed studies that show that there are beneficial effects on a bona fide health outcome or a recognized surrogate, e.g., LDL-cholesterol.

Frank M. Sacks, for the authors.

On 2017 Jun 30, Hilda Bastian commented:

The authors state that this advisory "reviews and discusses the scientific evidence, including the most recent studies", and that its primary recommendation is made, "taking into consideration the totality of the scientific evidence, satisfying rigorous criteria for causality". They do not report what evidence was sought and how, or the basis upon which it was selected. There is little in this report to suggest that "the totality of scientific evidence" was considered.

For example, four reviews of trials are referred to:

• Mozaffarian D, 2010 (date of last search June 2009)
• Chowdhury R, 2014 (date of last search July 2013)
• Hooper L, 2015 (Cochrane Collaboration) (date of last search March 2014)
• Mensink, 2016 (WHO) (date of last search December 2013)

However, the more recent systematic review and meta-analysis within Ramsden CE, 2016 (date of last search March 2015) was not mentioned. Nor are, for example, these systematic reviews: Skeaff CM, 2009; Stroster, 2013; National Clinical Guideline Centre (UK), 2014; Schwingshackl L, 2014; Pimpin L, 2016.

The AHA advisory includes sections reviewing two specific sources of saturated fat, dairy and coconut oil. Dairy products are a major source of dietary saturated fats. However, no basis for singling out coconut oil is offered, or for not addressing evidence about other, and larger, sources of saturated fats in Americans' diets. The section concludes: "we advise against the use of coconut oil".

There are three conclusions/statements leading to that recommendation:

• Eyres L, 2016 "noted that the 7 trials did not find a difference in raising LDL cholesterol between coconut oil and other oils high in saturated fat such as butter, beef fat, or palm oil."
• "Clinical trials that compared direct effects on CVD of coconut oil and other dietary oils have not been reported."
• Coconut oil increases LDL cholesterol "and has no known offsetting favorable effects".

The only studies of coconut oil cited by the advisory to support these conclusions are one review (Eyres L, 2016) - reasonably described as a narrative, not systematic, review by its authors - and 7 of the 8 studies included in that review. The date of search of this study was the end of 2013 (with an apparently abbreviated update search, not fully reported, in 2015). Not only is that too long ago to be reasonably certain there are no recent studies, the review's inclusion and exclusion criteria are too narrow to support broad conclusions about coconut oil and CVD or other health effects.

The AHA's first statement - that Eyres et al noted no difference between 7 trials comparing coconut oil with other saturated fats - is not correct. Only 5 small trials included such comparisons, and their results were inconsistent (with 2 of the 3 randomized trials finding a difference). There was no meta-analysis, so there was no single summative finding. The trials in question are very small, none lasting longer than eight weeks, and have a range of methodological quality issues. The authors of the Eyres review caution about interpreting conclusions based on the methodologically limited evidence in their paper. In accepting these trials as a reliable basis for a strong recommendation, the AHA has not applied as rigorous a standard of proof as they did for the trials they designated as "non-core" and rejected for their meta-analysis on replacing dietary saturated fat with polyunsaturated fat.

Further, even a rapid, unsystematic search shows that there are more participants in relevant randomized trials not included in the Eyres review than there are randomized participants within it. For example: McKenney JM, 1995; Ganji V, 1996; Assunção ML, 2009; Cardoso DA, 2015; de Paula Franco E, 2015; and Enns, 2015 (as well as another published since the AHA's panel finished its work, Shedden, 2017).

The conclusions of the coconut oil section of the AHA advisory are not supported by the evidence it cites. A high quality systematic review that minimizes bias is required to draw any conclusion about the health effects of coconut oil.

Disclosure: I have no financial, livelihood, or intellectual conflicts of interest in relation to coconut or dietary fats. I discuss my personal, social, and professional biases in a blog post that discusses the AHA advisory on coconut oil in detail (Bastian, June 2017).

On 2017 Jun 30, Hilda Bastian commented:

The authors state that this advisory "reviews and discusses the scientific evidence, including the most recent studies", and that its primary recommendation is made, "taking into consideration the totality of the scientific evidence, satisfying rigorous criteria for causality". They do not report what evidence was sought and how, or the basis upon which it was selected. There is little in this report to suggest that "the totality of scientific evidence" was considered.

For example, four reviews of trials are referred to:

• Mozaffarian D, 2010 (date of last search June 2009)
• Chowdhury R, 2014 (date of last search July 2013)
• Hooper L, 2015 (Cochrane Collaboration) (date of last search March 2014)
• Mensink, 2016 (WHO) (date of last search December 2013)

However, the more recent systematic review and meta-analysis within Ramsden CE, 2016 (date of last search March 2015) was not mentioned. Nor are, for example, these systematic reviews: Skeaff CM, 2009; Stroster, 2013; National Clinical Guideline Centre (UK), 2014; Schwingshackl L, 2014; Pimpin L, 2016.

The AHA advisory includes sections reviewing two specific sources of saturated fat, dairy and coconut oil. Dairy products are a major source of dietary saturated fats. However, no basis for singling out coconut oil is offered, or for not addressing evidence about other, and larger, sources of saturated fats in Americans' diets. The section concludes: "we advise against the use of coconut oil".

There are three conclusions/statements leading to that recommendation:

• Eyres L, 2016 "noted that the 7 trials did not find a difference in raising LDL cholesterol between coconut oil and other oils high in saturated fat such as butter, beef fat, or palm oil."
• "Clinical trials that compared direct effects on CVD of coconut oil and other dietary oils have not been reported."
• Coconut oil increases LDL cholesterol "and has no known offsetting favorable effects".

The only studies of coconut oil cited by the advisory to support these conclusions are one review (Eyres L, 2016) - reasonably described as a narrative, not systematic, review by its authors - and 7 of the 8 studies included in that review. The date of search of this study was the end of 2013 (with an apparently abbreviated update search, not fully reported, in 2015). Not only is that too long ago to be reasonably certain there are no recent studies, the review's inclusion and exclusion criteria are too narrow to support broad conclusions about coconut oil and CVD or other health effects.

The AHA's first statement - that Eyres et al noted no difference between 7 trials comparing coconut oil with other saturated fats - is not correct. Only 5 small trials included such comparisons, and their results were inconsistent (with 2 of the 3 randomized trials finding a difference). There was no meta-analysis, so there was no single summative finding. The trials in question are very small, none lasting longer than eight weeks, and have a range of methodological quality issues. The authors of the Eyres review caution about interpreting conclusions based on the methodologically limited evidence in their paper. In accepting these trials as a reliable basis for a strong recommendation, the AHA has not applied as rigorous a standard of proof as they did for the trials they designated as "non-core" and rejected for their meta-analysis on replacing dietary saturated fat with polyunsaturated fat.

Further, even a rapid, unsystematic search shows that there are more participants in relevant randomized trials not included in the Eyres review than there are randomized participants within it. For example: McKenney JM, 1995; Ganji V, 1996; Assunção ML, 2009; Cardoso DA, 2015; de Paula Franco E, 2015; and Enns, 2015 (as well as another published since the AHA's panel finished its work, Shedden, 2017).

The conclusions of the coconut oil section of the AHA advisory are not supported by the evidence it cites. A high quality systematic review that minimizes bias is required to draw any conclusion about the health effects of coconut oil.

Disclosure: I have no financial, livelihood, or intellectual conflicts of interest in relation to coconut or dietary fats. I discuss my personal, social, and professional biases in a blog post that discusses the AHA advisory on coconut oil in detail (Bastian, June 2017).

On 2017 Aug 06, Stuart Buck commented:

What bothers me most is the following statement from a study author: "Each of these increase LDL-cholesterol compared to carbohydrate and more so when compared to the unsaturated fats. This is sufficient to warn the public about anticipated adverse effects of coconut oil on CVD."

No, it is not. There are at least 5 treatments that lower LDL without lowering CVD, and sometimes even make CVD worse. See Table 1: http://www.nejm.org/doi/full/10.1056/NEJMp1508120?af=R&rss=currentIssue#t=article.

Nutritionists should not give advice based on trials about LDL while ignoring that LDL manipulation is often disconnected from or even directly contrary to CVD outcomes.