Saturated Fats in the News

Summary

A 2014 meta-analysis of prospective cohorts and clinical trials did not find a statistically significant association between saturated fat and heart disease.

For a long time, there has been a theory in mainstream nutrition that saturated fat causes the body to increase the production of cholesterol which, in turn, increases the risk of heart disease. This theory has not been without its detractors.

A large meta-analysis from the UK released this week caused quite a splash because it found that saturated fat was not significantly associated with heart disease (1). It wasn’t a complete surprise, as a 2010 meta-analysis of prospective observational studies had already produced similar findings (2).

The 2014 meta-analysis produced results for three different types of studies:

1. 32 prospective cohort studies analyzing self-reported dietary intake of fatty acids.

2. 19 prospective cohort studies analyzing blood levels of fatty acids.

3. 27 randomized, controlled trials of various fatty acid supplementation regimens.

The results were fairly consistent in that very few associations were statistically significant.

Among the cohort studies analyzing intakes, total saturated fat had a slight trend towards more cardiovascular disease. The only statistically significant finding was for trans fats increasing the risk of heart disease, while long chain omega-3s (EPA and DHA) were almost significantly associated with a lower risk.

Among the cohort studies looking at blood levels, total saturated fat again had a slight trend towards more cardiovascular disease. When looking at individual types of saturated fats, the common saturated fats found in animal products, palmitic acid and stearic acid, were more strongly associated with heart disease, though still not statistically significant.

Interestingly, the only fatty acids in the blood that were significantly associated with heart disease (all inversely) were margaric acid (a saturated fat found primarily in dairy products), the long chain omega-3 fatty acids (EPA, DPA, and DHA), and, more surprisingly, the long chain omega-6 fatty acid, arachidonic acid.

Arachidonic acid had previously been thought to be a cause of inflammation, and therefore heart disease (though other research has countered that idea, see Omega-6s: Not So Bad?).

In terms of clinical trials, only supplementation with omega-3s and omega-6s were analyzed and didn’t find any statistically significant associations, though EPA and DHA came close to being associated with a lower risk.

There were some errors in the version of the paper I have, but these errors did not alter the conclusion according to the attached notice.

So what should someone think about all of this?

One of my regular readers suggested that if you take a bunch of studies with measurement error and throw them all together, you shouldn’t be surprised that you don’t find anything. Perhaps – I don’t know enough about biostatistcs to be able to assess that sort of thing.

Here is what I believe: The primary saturated fats found in animal products, palmitic and stearic acid, most likely contribute to an increase in cholesterol and an increase in the risk of heart disease for people who have high cholesterol. But what is probably more important is not eating too many calories. Fiber is also probably as important as saturated fat, if not more so (3), because it can transport cholesterol out of your system.

Speaking of saturated fat, Dr. Michael Greger’s latest video on low-carb diets might be relevant, Low Carb Diets and Coronary Blood Flow.

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References

1. Rajiv Chowdhury, Samantha Warnakula, Setor Kunutsor, Francesca Crowe, Heather A. Ward, Laura Johnson, Oscar H. Franco, Adam S. Butterworth, Nita G. Forouhi, Simon G. Thompson, Kay-Tee Khaw, Dariush Mozaffarian, John Danesh, Emanuele Di Angelantonio; Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary RiskA Systematic Review and Meta-analysis. Annals of Internal Medicine. 2014 Mar;160(6):398-406. | link

2. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010 Mar;91(3):535-46. | link

3. Threapleton DE, Greenwood DC, Evans CE, Cleghorn CL, Nykjaer C, Woodhead C, Cade JE, Gale CP, Burley VJ. Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ. 2013 Dec 19;347:f6879. doi: 10.1136/bmj.f6879. | link

17 Responses to “Saturated Fats in the News”

  1. Idan Says:

    have you seen Willet’s response ?

    https://www.hsph.harvard.edu/nutritionsource/2014/03/19/dietary-fat-and-heart-disease-study-is-seriously-misleading/

  2. Jack Norris RD Says:

    Idan,

    I saw a response on Medscape Medical News that is probably similar (it even quoted people from Harvard), but I didn’t find the counter-arguments terribly compelling. I’m running out the door and will check this article out later. Thanks!

  3. Dan Says:

    None of this meta-analysis or the preceding one in JACN tell me as much as a single large randomized trial of replacing saturated fat with something else, much as a vegan diet would tend to do. So, a study like Ornish et al but on a much larger scale.

  4. Dan Says:

    Another issue with this meta-analysis is that even the blood marker studies are confounded. It’s possible that richer, more socioeconomically advanced people have higher blood levels of saturated fatty acids because they can afford to eat more “steak and bacon”; whereas poor people may only be able to eat staple foods (rice, bread) – at least outside the USA. Unfortunately, socioeconomic status is strongly tied to cardiovascular and coronary events – poor people live shorter, nastier, more brutal lives (to paraphrase Hobbs). To what extent the individual studies adjusted for SES in their analyses is unclear to me, as many people refuse to divulge annual household income, and even that is not a great measure of social standing, education, etc. Give me a trial!

  5. James Says:

    The list of meta-analysis studies includes one done by Patti Siri-Torino. There are very serious shortcomings with many of the studies that she and her fellow researchers chose to include in their meta-analysis. These shortcomings are extensively documented in the following two videos. I think that any conclusions based on the results of the meta-analysis have no basis in fact. Also noted was the associations of the authors. Both Siri-Torino and Krauss are on on the payroll of the dairy and beef industry. Does anybody think that they are going to come to a conclusion that threatens one of their primary funding sources? Much more likely is that they will produce something that, like tobacco “researchers” of a generation ago, adds to the confusion about the association between saturated fat and animal foods and CHD and stroke.

    http://www.youtube.com/watch?v=a-Tx9dCbv-g

    http://www.youtube.com/watch?v=3Wi9dzkTiU4

    These are part of a longer series of videos produced by someone calling himself “plant positive”. I think his analysis is very compelling since he uses the very papers cited by those who say that saturated fat and animal foods aren’t strongly correlated to ones risk of developing CHD and the other “western” diseases. He says that he chose to remain anonymous so that he wouldn’t become the issue and so we could focus on the analysis of what he is presenting. I highly recommend viewing all the videos in this and the other series that he has produces. There is a lot of them, but I certainly come out with a much stronger appreciation for how truly bad some of the “science” used by those who promote a high animal food diet truly is.

  6. Paul B Says:

    Dr. David Katz of Yale’s take on the study.

    http://www.huffingtonpost.com/david-katz-md/diet-and-nutrition_b_4985323.html

  7. Ayla Says:

    Thanks for your take on things. The research on fats continues to confuse me but by removing animal products and adding some coconut oil I feel relatively safe for now.

    A bit off topic, I was wondering whether you’ve come across this recent paper from Austria that doesn’t paint a too shiny picture of vegetarianism (veganism isn’t mentioned): http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0088278
    They already mention some pitfalls but if it interests you I’m also curious of your opinion.

  8. Jack Norris RD Says:

    Ayla,

    I posted a write-up on another paper the Austrian group wrote:

    http://jacknorrisrd.com/austrian-vegetarians-good-news/

    In that paper, they were more positive about a vegetarian diet, but I thought it was a poorly conducted study. I haven’t read the one you reference, but I’ve been hearing a lot about it so perhaps I should.

  9. Dan Says:

    Jack, what is your opinion on using coconut milk in cooking, such as in Thai dishes (like yellow coconut curry)? The ingredients state it is rich in saturated fat, but it’s a plant-based saturated fat, and contains no cholesterol. Obviously more ethical than using whole milk, but is it healthy?

  10. Jack Norris RD Says:

    Dan,

    I am planning on writing an article on coconut milk because it’s now the most common question I get. I reviewed all the research on it awhile back (without writing an article, just for my own interest) and it seemed to me that coconut oil raises cholesterol levels but coconut meat does not. That said, I think that unless you have high cholesterol, a moderate amount of coconut oil is probably fine.

  11. Dan Says:

    Hi Jack, I was referring to coconut milk not coconut oil. Anyway, in light of coconut milk, the following article, which is free online, was interesting:

    http://www.ncbi.nlm.nih.gov/pubmed/24282632

    Having read through the study design, it is possible that there are some biases here (lack of randomization, not really a true crossover design, and no tracking of what food products were *replaced* in the diet with the coconut milk). Thus I am a bit reluctant to believe these data. I will continue to use coconut milk in moderation, mostly in a commercially prepared coconut curry dish.

  12. Jack Norris RD Says:

    Dan,

    > I was referring to coconut milk not coconut oil.

    But the question regarding whether coconut milk is healthy is because it contains coconut oil, right?
    http://jacknorrisrd.com/wp-admin/edit-comments.php?p=5341&approved=1#comments-form
    Interesting study, thanks.

  13. unethical_vegan Says:

    http://news.sciencemag.org/health/2014/03/scientists-fix-errors-controversial-paper-about-saturated-fats

    I agree that this manuscript should be retracted.

  14. coffeebrain Says:

    Every few months I check in with your blog. I should really do it more. You give us the best information.

    Personally, I don’t think saturated fat is an issue. Then again, I don’t eat meat, fish, fowl, eggs, poultry, so the only significant saturated fats I get are from coconuts/oil, organic palm shortening that I use in baking, etc. I don’t worry about it too much.

    Honestly, I think twice about Harvard’s Willet’s responses. He’s the one who said low body weight means more for health than what you eat. Yeah, tell that to my grandpa (rest in peace granddaddy), who was skinny as a rail and suffered from poor health and ate an animal-rich diet.

  15. MacSmiley Says:

    Travis “Healthy Longevity” HL has posted an extensive review of this study. The factors I find that are the most compelling demonstration of skewed results are:

    Clearing Up The Confusion Surrounding Saturated Fat

    http://healthylongevity.blogspot.com/2014/03/saturated-fat-heart-disease-meta-analysis.html?m=1

    1. Over adjustments —Subjects with high cholesterol were filtered out of the study pool, the very people who would be most affected by saturated fat.

    2. The range of saturated fat intake was only between 5% and 10% of total calories. Hardly a big enough contrast.

    I don’t think we can throw away nearly a century of research on this, including animal studies, human ward studies, and cell studies, not to mention the epidemiology.

    Researchers are forgetting how many non-obese, non-diabetics dropped dead of heart attacks at the peak of the epidemic in the 1950s, 60s, and 70s. New demographics are skewing their perception.

  16. Alex Says:

    The french eat tons of saturated fat, 3x more than americans yet have lower cardiac risk. They eat less processed junk food.

    Also with folks on very low carb diets who eat tons of saturated fat, many have zero calcified plaque practically.

    An interesting way to possibly answer this question is to compare lacto-vegans to non lacto-vegans, both consume lots of carbs, however lacto-vegans probably consumer saturated fats via pizza,butter,cheeses, and possibly dairy. India particularly south india has one of the highest rates of diabetes and heart disease in the world, however being a lacto-vegan is common, and I presume that even those that eat meat, have have most of their diet lacto-vegan.

    Note the term lacto-vegan is misleading because many south indians are lactose intolerant, so they probably won’t be having too much cow milk, also cheese dishes such as pizza, mac n cheese, pastas,etc are not a staple indian cuisine. South Indian cuisine does not usually have many cheese dishes and its not the main part of meal besides one cheese called paneer which is usually only added to maybe spinach dishes.

    That leaves out butter and oils for the most part, a comparison won’t be easy.

  17. Jack Norris RD Says:

    Alex,

    Check out Michael Greger’s videos about the Mediterranean diet:

    http://nutritionfacts.org/video/which-parts-of-the-mediterranean-diet-extended-life/

    In this one, he says, “If you look at the baseline adherence to Mediterranean diet principles, and control for things like smoking and exercise, there were only two factors significantly associated with reduced heart attack and stroke risk, more vegetables and more nuts….No significant association with the olive oil or the wine or the fish or cutting back on soda and cookies….Maybe this is just because people may eat nuts instead of meat, eggs, and dairy, and that’s why they live longer? No, since vegetarians that frequently eat nuts also have a dramatically reduce risk compared to those that don’t.”

    My main point being that it’s possibly the nuts.

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