The ongoing, seemingly endless nutrition debate about what constitutes a healthy diet just got a little hotter. In recent weeks a new book entitled The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet  hit bookstore shelves, and was followed by an article in the current issue ofTime magazine called “Ending the War on Fat.” The primary message of both the book and the article is that the past fifty years or so of diet advice dispensed by various health agencies, and countless research studies performed on the diet/heart disease relationship, have been mostly flawed. And before you discount these two recent sources as the work of lay authors, it should be pointed out that a couple of well-done, albeit controversial, meta analyses out of UC-Berkeley  andCambridge University  in England largely support the principal conclusions of the book and the Time article -that current evidence does not support low consumption of saturated fats or cholesterol as antidotes to cardiovascular disease (CVD).
How did this change in thinking come about, and where might it lead us in the future? Regarding the former, the realization that fifty years of dietary advice (that was mostly adhered to by a large segment of the population) suggesting we eat less red meat, fewer eggs and less dairy products has done little to limit the rate of CVD in the U.S. and that at the same time we were becoming more and more overweight and obese as a nation, has caused many health experts to re-evaluate the data on which these recommendations were based. And what this re-analysis indicates, among other things, is that the majority of the studies on which macronutrient intake recommendations are based were epidemiological studies, which are great for hypothesis generation but marginal for establishing cause-and-effect. Worse yet, information gleaned from some of these studies have been extrapolated or inferred to help create a story that may not exist. Both the aforementioned book and Time article tell the story of how some of the data from Ancel Keys’ well-known Seven Countries Study was apparently cherry-picked so that only data from countries that supported a saturated fat/CVD relationship were included in Keys’ analysis, and countries that did not fit this paradigm were excluded.
Another point worth noting is the possible unintended consequence of food substitution: if a person adheres to dietary advice suggesting less saturated fat and cholesterol consumption, what would he/she likely add into the diet to make up for the nutritional and caloric shortfall created by removing fats? The answer is, of course, carbohydrates. Primarily refined carbs and sugars. And newer research indicates that many of the consequences of a low fat/high refined carb diet – elevated triglycerides, decreased insulin sensitivity, more small, dense LDL particles, greater vascular inflammation, increased body weight, etc. may be the real culprits in elevated CVD risk. Ironic, isn’t it, that the foods once promoted as a healthier alternative to higher fat fare may turn out to be “the bad guys” after all?
Where will this new information lead? Still too early to tell. As any nutrition professional can tell you, diet research is fickle, and alternative hypotheses on what constitutes the healthiest diet will undoubtedly change many times in the future as new data become available. One thing that seems obvious is our need for more diet-based studies, and less single-nutrient research. When single nutrients are studied outside the context of the entire diet, misinterpretations are bound to occur. For example, dietary cholesterol as a part of a diet loaded with fruits and vegetables, whole grains, and various healthy fats and proteins may be largely innocuous; the same amount of cholesterol in a high calorie, high sugar and refined carb diet may be disease-promoting.
A healthy re-evaluation of the data on which we’ve based many of our dietary beliefs is certainly in order if we’re ever to move closer to understanding what constitutes a truly healthy diet.
1. Teicholz N: The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.Simon & Schuster; 2014.
2. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM: Saturated fat, carbohydrate, and cardiovascular disease. The American Journal of Clinical Nutrition 2010, 91:502-509.
3. Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, Franco OH, Butterworth AS, Forouhi NG, Thompson SG, et al: Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Annals of Internal Medicine2014, 160:398-406.