Featured article in the Winter 2015 Issue of Nutrition Close-Up; written by David C. Madsen, PhD
This is a short account of science not about how it is done but more about what is done with its results. It is also about learning from our mistakes. Will we?
Nina Teicholz wrote in the Fall 2014 issue of ENCs Nutrition Close-Up1 about the seminal work of Dr. Ancel Keys and colleagues. She recounted their thoughtful and innovative studies on the relationships between diet and health in the 1950s, in this case heart disease (HD). The overall conclusion was that excess dietary fat and cholesterol were strongly linked to HD. Continuing research refined the information and distinguished dietary saturated fatty acids (SFA) as bad fat, while polyunsaturated fatty acids (PUFA) was good fat. Additionally, the negative role of trans fats, an artifact of manufacturing, was deduced.
As is now well known, the good and bad dietary fats are designated as such because of their effects on cholesterol and triglycerides concentrations in the bloodstream. The cholesterol fraction was determined to exist in two states: good cholesterol (in HDL*) and bad cholesterol (in LDL*). A goal of blood health thus came to be: more HDL is better; less LDL is better. The relationships between dietary fats and blood fats (lipids) can be summarized, very simply, for illustrative purposes:
Application The research produced conclusions that, while not exceedingly complex, were nuanced, meaning that attention to detail was important in their interpretation. During the transition from acceptance of research to creation of guidelines (by National Heart, Lung, and Blood Institute, American Heart Association, and others) and subsequently into public messaging, some of the nuance was omitted. Policy makers wanted simple, practical messages, which led to over-simplified statements, such as reduce total fat intake. Doing so, of course, does indeed reduce intake of bad fats. Research and messaging continued on the health benefits of dietary PUFA, but the concept was not communicated well and ran against the low-fat mantra that had been put in place.
As a result, low-fat diet campaigns were launched, which spread to cookbooks. The food industry responded with a myriad of low-fat products. The process of reformulating foods to be low in fat necessarily meant replacement of the fat, typically with carbohydrate, and usually with the least costly types, including maltodextrins and sugars. Thus, even where saturated fat intake was reduced, caloric intake was not (these are generalities, of course). And in the process, ingredients and nutrients got most of the attention, while total calorie intake, balanced diets, and whole foods were de-emphasized.
Today A large analysis published this year by Chowdhury et al.2 in the Annals of Internal Medicine addressed the official recommendations for dietary fat consumption. After reviewing many previous studies the paper concluded: current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fat. This appeared to be in conflict with what had become conventional wisdom.
The Chowdhury study unleashed a feeding frenzy by some in the science press. The cover of Time magazine touted: Eat Butter. Scientists labeled fat the enemy. Why they were wrong. 3 As often happens, the more sensational and inaccurate the stories became, the more attention they got.
Meantime, some inconsistencies were identified in the study, e.g. certain key data were not included. Letters to the editor flew; public and private discussion occurred. Study authors were amazed by the inaccurate or exaggerated reporting, due in part to the wording of the conclusions. The senior author of the Annals study offered that the paper only showed that the story on saturated fat is slightly more complicated than we thought.4 In fact it is clearly presented in the discussion portion of the paper that while conclusions do follow from the data, there are several potential and actual limitations of the data and the analysis that could have accounted for the conclusions.
Lessons This case study illustrates that translation of research into public policy is not easy to do faithfully, or quickly. Confusing recommendations, combined with clever advertising, served in this case to narrow our attention to the level of individual food ingredients, and even to nutrients. And this occurred at the expense of food, diet, and lifestyle. We seem to have forgotten how to eat, and in the process, how to live well.
I contend that the science, in this case, was not wrong. Where we messed up is what we did with the information we erred on how the science was communicated and applied.
There have been attempts recently to put whole foods back at center stage. We are developing more realistic food-based recommendations and dietary patterns. We will be better off talking about foods, and about balance and lifestyle. Have we learned from this experience? Can we now get it right? I finish with two contrasting responses.
- First is the recent storm of attention paid to sugar in its various forms. Scathing attacks paint sugar as something approaching evil, prompting calls at all levels to limit it, or even eliminate it, from all food. Doing so, they say, will result in better health for all. Sound familiar?
- The second is a news story by chef Yotam Ottolenghi, who said: instead of eliminating fat from my diet I revel in it daily a healthy balance alongside lots of green veg and roots; animal protein as well as protein from lentils, nuts and dairy products, fruit, grains, seeds, spices and different beans; and sugar too, sometimes unrefined, in dark chocolate or lightly whipped cream. 5
Perhaps Chef Ottolenghi should write out dietary recommendations. At the very least e can come to my house anytime.. sas look as he cooks.
David Madsen, PhD, has worked in the nutrition, food and pharmaceutical industries for more than three decades, and occasionally writes on topics of interest in those areas.
References
1. Teicholz N, Update: saturated foods not so bad after all. ENC Nutrition Close-up Fall 2014 Internet: https://www.enc-online.org/health-professionals/nutrition-close-up/nutrition-close-up-fall-2014/
2. Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, Franco OH, Butterworth AS, Forouhi NG, Thompson SG, Khaw KT, Mozaffarian D, Danesh J, DiAngelantonio E. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014;160:398-406.
3. Walsh, B. Ending the war on fat. Time, June 23, 2014.
4. Moran, B., Is butter back? Harvard Public Health, Fall, 2014.
5. Ottolenghi, Y., 2014. Fats the way to do it. http://www.theguardian.com/lifeandstyle/2014/oct/10/fenneltarte-tatin-recipe-yotam-ottolenghi-croque-harissa-pommes-dauphine