To Cut or Not to Cut Saturated Fat Intake: What Do Evidence-Based Data Say?

Lawrence J. Appel, MD, MPH; Alice H. Lichtenstein, DSc


June 29, 2015

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Lawrence J. Appel, MD, MPH: Hello. My name is Dr Lawrence Appel, and I am the C. David Molina Professor of Medicine in the Department of Epidemiology and Clinical Research at Johns Hopkins University. I am here with a colleague of mine, Dr Alice Lichtenstein, who is the Stanley N. Gershoff Professor of Nutrition Science and Policy and the Director of the Cardiovascular and Nutrition Laboratory at Tufts University. Both of us were speakers at the American Diabetes Association Scientific Sessions held in Boston, and both of us participated in a session on controversies in nutrition. We are going to discuss the major findings that we wanted to convey to the audience. Alice, you spoke about saturated fats. Will you tell us what the key messages were?

Alice H. Lichtenstein, DSc: One of the things I wanted to address was the controversy over saturated fats. For many years, we've had a recommendation to limit saturated fat intake to decrease the risk for cardiovascular disease. Some recent meta-analyses[1] have questioned the wisdom of that advice. What I did was really delve down to what the basic facts were from some of the early literature, where a lot of what we know about saturated fat and dietary fat emerged, and what really contributed to our current recommendations.

One of the most important points is that when saturated fat in the diet is changed, some other component of the diet is changed as well. One needs to take into consideration both the change in saturated fat as well as what it has been replaced with. Early data indicated that by replacing saturated fat with polyunsaturated fat, there was a clear benefit with respect to cardiovascular disease risk. Replacing saturated fat with carbohydrate, which is a recent phenomenon, does not have a benefit.

Many of the meta-analyses that questioned the wisdom of the current recommendation to restrict saturated fat did not distinguish between the macronutrients that were used to substitute. That is why we currently have so many mixed messages. That is why we see people saying, "Butter is back. We don't have to restrict saturated fat. The scientists were wrong." And that is an unfortunate occurrence. We need to provide very clear and concise recommendations to the American public, and that is to replace saturated fat with unsaturated fat—primarily polyunsaturated fat—and not carbohydrates, particularly refined carbohydrates.

Dr Appel: I just wanted to pick up on one thing. The studies that you said were older were actually clinical trials, weren't they?

Dr Lichtenstein: They were. They were intervention studies in which people were counseled and in some cases provided with some of the components, the fat. The endpoints were actually hard endpoints, so there were coronary heart disease events and cardiovascular deaths.

Dr Appel: And some of the studies that contributed to the meta-analyses were observational studies, cohort studies.

Dr Lichtenstein: In some cases that was true as well.

Dr Appel: For carbohydrates, especially.

Dr Lichtenstein: Yes. I know that you addressed issues related to dietary patterns, and that dovetails quite well with what I was addressing about having to take multiple components of the diet into consideration for dietary change and intervention studies. Could you tell me a little bit about the highlights of what you spoke about?

Dr Appel: I spoke about dietary patterns, and they're important because that's what individuals eat. They eat a whole diet. Although nutritionists have often focused on individual nutrients, that's not how people eat. I spoke about dietary patterns that have been recommended: the DASH diet, a variant to that called the OmniHeart diet, and the Mediterranean diet. I also discussed the studies that supported them.

I spent a lot of time on the PREDIMED study,[2] a randomized trial conducted in Spain in which individuals received counseling on how to follow the Mediterranean diet. They were also given large quantities of extra virgin olive oil. Another group got a fairly large quantity of nuts. A third group, the control group, didn't get either of those. It was remarkable because the groups that were advised on the Mediterranean diet and were given the extra virgin olive oil or the nuts both did better in terms of cardiovascular outcomes, particularly stroke. Based on the evidence that was presented, it looked like it could be a blood pressure effect because of how fast it occurred.

I also wanted to point out that these dietary patterns that are presented as distinct are actually quite similar. There is a lot of overlap in terms of the components. For example, they all were reduced in saturated fat. They often emphasized fruits, vegetables, dairy (low fat, if it's consumed), seeds, nuts, and legumes. They had very, very few sugar-sweetened beverages, very few desserts, and not much red meat. These dietary patterns are actually quite similar and not dissimilar, even though we tend to put them in separate buckets.

Dr Lichtenstein: You do talk about dietary patterns but not very prescriptively. Would you say that they could be adapted to individual personal preferences or cultural backgrounds?

Dr Appel: I think that is quite true. There was a wide range of macronutrients that could be consumed, so some could be pretty high in olive oil. Others could be higher in desirable carbohydrates but not added sugars. There is quite a bit of flexibility, although I wouldn't say that food from a deep fryer enters into any of those diets.

Dr Lichtenstein: So generally something high in vegetables, fruits, whole grains, fish, low- or nonfat dairy, legumes, nuts, and seeds.

Dr Appel: Right. Plant-based, for the most part.

Dr Lichtenstein: Although fish could probably be very beneficial.

Dr Appel: Sure. There is some controversy about that, and we didn't necessarily cover it in detail today, but fish and fish oil are a bit under the microscope as well.

Dr Lichtenstein: But perhaps to replace the meat that is high in saturated fat or cheeses that are high in saturated fat?

Dr Appel: Sure.

Dr Lichtenstein: So again, it goes back to: If you're not eating one thing, what are you substituting it with?

Dr Appel: And that's typically what happens. If somebody has fish, they're not eating a steak.

It has been a pleasure chatting with you, Alice. I hope today's session was of interest to the listeners on Medscape. It certainly was an informative session, and I hope we conveyed the excitement and interest in the topics that we covered. Thank you.

Dr Lichtenstein: Great talking with you, Larry.


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