Fat in the diet is a highly complicated issue. For decades, we have adopted the notion that fat may be the enemy and, therefore, we should eat a low-fat diet. But is this really true? The answer is that we all need fat, but the sources are important.
The cover of Time magazine’s June 23 edition exclaimed in big yellow letters to “Eat Butter. Scientists labeled fat the enemy. Why they were wrong” (1). It also included a picture of a curl of butter, in case you had forgotten what butter looked like. This cover is provocative and tantalizing. However, it does a disservice to the article itself and to the general population who may have seen it.
The article, itself, is well written. Its focus is not mainly on butter, but rather on different types of fats, saturated and unsaturated. The author Bryan Walsh does make salient points, but my objection is mainly that many of these points are buried deep within a five-page, three-column, single-spaced article among comments that are not necessarily substantiated. You have to wade through paragraph after paragraph to get to some these points. Reading the first page is not good enough.
Let’s look at a few studies presented in the article.
Study: Different types of fat — saturated and unsaturated with heart disease.
There was a recent meta-analysis (a group of 72 studies including both observational and randomized controlled trials) that looked at whether different types of fat had an impact on cardiovascular health (2). The results showed that saturated fats, omega-6 polyunsaturated fats and monounsaturated fats were most likely not harmful and that omega-3 polyunsaturated fats were potentially beneficial. However, trans fatty acids were shown to be potentially harmful, with a 17 percent increased risk of cardiovascular disease outcomes such as heart attacks and heart disease.
While this is an interesting study, there are some significant flaws that need to be highlighted.
1. The conclusions in the study don’t match or only partially match. Let me explain. There is a conclusion in the abstract (a synopsis or summary of the study) and a conclusion in the body of the study. The abstract concludes that polyunsaturated fats, including omega-3 fatty acids, are not necessarily beneficial while saturated fat may not be harmful. In the body of the study, the authors conclude that omega-3 fatty acids significantly reduce cardiovascular events. Why is this important? Many physicians are bombarded by studies and may only have time to read the abstract. Thus, this could wrongly influence the physician.
2. The source of fat is never differentiated in the study. In other words, the saturated fats which are deemed harmless may be from foods or supplements that contain both unsaturated fats and saturated fats or from foods that contain only saturated fats. We see benefit in plant-based foods that have multiple types of fats — saturated and unsaturated — such as olive oil, nuts, seeds and avocado. However, most animal fats, like red meat, pork and chicken, contain only saturated fats. The exception is fish, which contains multiple types of fats.
Also, unlike the Time cover story, the study NEVER mentions butter, cheese or red meat. Therefore, the commentary by the press is based on an extrapolation that cannot and should not be made: that eating butter, cheese and red meat maybe harmless and possibly beneficial.
3. The populations of the studies differed at the starts of the different trials. In other words, some were healthy participants, some were high-risk patients and some already had cardiovascular disease. The main thing these studies had in common was that cardiovascular disease outcomes were an endpoint, but it did not have to be the primary, or main, endpoint. Thus, cardiovascular disease outcomes may not have been the main thrust of all the studies that made up the meta-analysis.
4. A meta-analysis by definition is difficult to perform because researchers combine results from studies that were designed and performed differently from one another. In this meta-analysis, the authors combine the results of observational trials that may have used different types of fat intake from food or from supplements. Usually, supplements, like fish oil, involve both saturated and unsaturated fats, and they may have different effects than food.
5. Finally, the study does not tell us what those who ate lower saturated and unsaturated fats ate instead. For example, it compared those who ate high saturated fats to those who ate low saturated fats. What did the group who ate lower saturated fat eat instead of fat? Was it carbohydrates? If so, were they fries, whole grains or sweet potatoes?
The Time cover article goes on to mention the Mediterranean diet and its beneficial effects with heart disease. There was a recent randomized controlled study, the gold standard of studies, called the
PREDIMED trial, with results that showed that participants who ate a Mediterranean diet with added olive oil or mixed nuts had a 30 percent decreased risk of cardiovascular disease than those in the control arm who were advised to follow a “low-fat” diet (3).
The Mediterranean diet emphasizes vegetables, fruits, whole intact grains, beans, legumes and fish, as well as olive oil and nuts. This was not a low-fat diet. It contained both saturated and unsaturated fats, including polyunsaturated and monounsaturated fatty acids. The caveat to these results is that the “low-fat” group was not actually able to maintain a low-fat diet, but instead ate more like the standard American diet with no restrictions.
Interestingly, researchers using the same Mediterranean diet study, PREDIMED, showed that higher dietary intake of magnesium reduced the risk of cardiovascular mortality risk by 34 percent (4). They compared those in the highest intake of dietary magnesium with those in the lowest. These participants had a high risk of cardiovascular disease. Foods rich in magnesium include dark green leafy vegetables, such as spinach, as well as nuts, seeds, fish, beans, lentils and avocados.
In conclusion, the sources of fats matter. To run out and eat a cheeseburger, without the bun of course, would be to have misunderstood this article and the flaws in the meta-analysis and to have focused only on the cover of the Time magazine article.
The take-home message should be that we need some fats in our diet, but that the sources of these fats are critical. Diet quality is of the utmost importance in reducing disease (5), so put that cheeseburger out of your mind. Many studies have shown that the Mediterranean diet helps reduce the risk of cardiovascular events. For some, this may include the addition of more olive oil and nuts.
(1) Time.com. (2) Ann Intern Med. 2014;160:398-406. (3) N Engl J Med. 2013;368:1279-1290. (4) J Nutr. 2014;144:55-60. (5) Lancet. 2014;383:1999-2007.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website medicalcompassmd.com or consult your personal physician.