From the Harvard School of Public Health: Butter is not back: Limiting saturated fat still best for heart health

Excerpt:

People who replace saturated fat (mainly found in meats and dairy foods) in their diets with refined carbohydrates do not lower their risk of heart disease, according to a new study led by researchers at Harvard T.H. Chan School of Public Health. On the other hand, those who replace saturated fats with unsaturated fats (found in vegetable oils and nuts) or whole grains lower their heart disease risk.

In February, the 2015 Dietary Guidelines Advisory Committee submitted the Scientific Report of the 2015 Dietary Guidelines Advisory Committee which gives recommendations to the U.S. Department of Health and Human Services (HHS) and the U.S. Department of Agriculture (USDA) for the upcoming Dietary Guidelines. The Advisory Report is not the final Dietary Guidelines.

Of note, the Advisory Committee removed the advice to reduce dietary cholesterol and the advice to include lean meat. Ginny Messina, RD wrote a good summary of what this means for animal advocacy in her article, The 2015 Dietary Guidelines: What Will They Mean for Vegans?

On February 20, the New York Times ran an opinion piece, The Government’s Bad Diet Advice, by Nina Teicholz. It’s the typical Weston Price-type, pro-animal-product piece, in the same vein as writings by Nina Planck (no, they are not the same person).

David L. Katz, MD, MPH wrote a fun response to Teicholz’s piece, We’re Fat and Sick and The Broccoli Did It!

And speaking of Dr. Katz, he recently wrote a thoughtful piece on the Paleo diet, Paleo for a Shrinking Planet?

Nutrition-wise, I have been working on a resource on zinc for the Vegetarian Nutrition Dietetic Practice Group.

The only new info from that research that I had not been considering before is that people who eat a lot of soy and who take calcium supplements might have higher zinc needs. Since I fall into both those categories, I’m wondering if that’s why I seem to benefit so much from zinc. I’m happy to report that I still have not gotten more than the mildest and shortest of colds since starting zinc supplements a number of years ago.

Many links I’ve wanted to share with readers have been building up and so I’m going to knock them all out in one post right here.

Regarding the report suggesting saturated fat intake has no bearing on heart disease (see Saturated Fats in the News), Dr. Rose Marie Robertson of the American Heart Association wrote a response worth sharing: Chief Science Officer ‘sets record straight’ about diet, science, AHA.

Examine.com is a website with a panel of health writers who research a wide array of nutrition supplements and other topics. They appear to do an excellent job of assessing the research. Along with the Linus Pauling Institute at Oregon State University and the Office of Dietary Supplements, I can see Examine.com as being one of my go-to sites for seeing what research is out there.

Speaking of go-to sites, Dr. Michael Greger of NutritionFacts.org has just released Latest in Clinical Nutrition: Volume 19.

On March 10, the Washington Post ran an article (originally appearing in NewScientist) suggesting that many species of invertebrates feel pain: Do lobsters and other invertebrates feel pain? To summarize the article: octopi, squid, lobsters, crabs, and shrimp: yes. Insects: no.

Speaking of invertebrates and pain, there is a movement among some animal protectionists to promote bivalveganism. See The Ethical Case for Eating Oysters and Mussels – Part 2 at Sentientist. The author, Diana Fleischman, argues that bivalveganism can solve many of the nutrition dilemmas posed by vegan diets such as B12, iron, omega-3s, and zinc. It does seem like a decent solution for people who find it hard to thrive on vegan diets.

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.

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