The Big Fat Controversy
Posted by , MS, RD, CDE

Both consumers and healthcare professionals struggle with the question of whether or not saturated fats are harmful or neutral to health. Even as I dig into the research, I still have questions. I was fortunate to hear Penny Kris-Etherton, PhD, RD, Distinguished Professor of Nutrition at Penn State University speak on this topic at the Today’s Dietitian Symposium in New Orleans last May. I followed up with a few questions to Dr. Kris-Etherton. Here’s a summary.

Q: Why is there so much controversy about dietary saturated fats and if they are harmful or not?

A: There are a few epidemiological studies suggesting that dietary saturated fats acids (SFA) are not harmful to health.  But, these studies didn’t evaluate what participants consumed instead of eating saturated fats. If people are eating other types of unhealthful foods – like highly processed carbohydrate-rich foods – their health outcomes are no better. Some people interpret this to mean that SFAs do not adversely affect heart health. But, in reality, it just means that foods rich in saturated fats are as unhealthful as other poor choices. More recent research has shown that when monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), whole grains and/or plant protein are substituted for SFAs, the risk for heart disease decreases.

Bottom line: SFAs are harmful to the heart compared to unsaturated fats, whole grains and plant proteins. The total diet matters, not just whether or not an individual consumes hard fats or liquid oils.

Q: What does the science tell us about coconut oil and heart health?

A: A recent review concluded that coconut oil does not benefit the heart.[i] Studies show that coconut oil raises both total cholesterol and LDL-cholesterol levels compared to liquid oils like canola and olive oils, but butter raises these cholesterol fractions even more than does coconut oil. Coconut oil is often touted as healthful because it’s mistakenly compared to medium chain triglycerides (MCTs), which are absorbed predominantly in the portal circulation and metabolized differently in the body than the longer SFAs. But this is a misguided comparison because coconut oil contains very little capric and caprylic acids. The major long chain saturated fatty acid is lauric acid, (C12:0). Scientists question whether lauric acid is even a MCT because while a small proportion is absorbed via the portal circulation, most is absorbed via chylomicrons just like long chain fatty acids. Only about 13% of coconut oils’ SFAs are true medium chains.

Bottom line: Coconut oil unfavorably affects cholesterol levels. Also, it is questionable whether the major fatty acid in coconut oil is even a MCT because most of its major fatty acid is absorbed like a long chain fatty acid. A new American Heart Association Presidential Advisory clearly discourages the use of coconut oil and encourages the use of oils with predominantly unsaturated fats in its place.[ii]

Q: What does the science tell us about dairy fat and diabetes prevention?   

A:  Several studies have shown that dairy fat is protective of diabetes.[iii] But we don’t have enough solid data to recommend whole milk dairy to prevent type 2 diabetes.

Bottom line: Because having type 2 diabetes dramatically raises the risk of heart disease and dying from heart disease, we need more research before recommending high fat diary foods, which may have negative effects on cardiovascular risk factors.

 

 

[i] Eyres L, Eyres MF, Chisholm A, Brown RC.

Nutr Rev. 2016 Apr;74(4):267-80. doi: 10.1093/nutrit/nuw002. Epub 2016 Mar 5. Review.  https://www.ncbi.nlm.nih.gov/pubmed/26946252

[ii] Sachs et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory from the American Heart Association.   http://circ.ahajournals.org/content/early/2017/06/15/CIR.0000000000000510

[iii]  Circulation. 2016 Apr 26;133(17):1645-54. doi: 10.1161/CIRCULATIONAHA.115.018410. Epub 2016 Mar 22. https://www.ncbi.nlm.nih.gov/pubmed/27006479#