It should come as no surprise to most people that there is dissent in the ranks of those who profess knowledge about the best nutrition for human beings. During the last decade or two views on the healthiest way to eat have branched off in many different directions from which conflicting ideas are hotly, and sometimes even viciously, debated. This state of affairs is not a productive one for anyone trying to make an intelligent decision on healthy eating. The various theories surrounding a definitive optimal human diet are so far apart that it would seem to be impossible to find any common ground.
For example, read the following diet guidelines from some currently popular diets. It’s easy to see that they run the gamut from having no limit on a certain type of food to avoiding it completely (1,2,3,4);
Eat mostly meat VS Eat only wild or grass-fed meat VS Eat no meat at all
Partake in only high fat dairy VS Ingest no dairy at all
Butter is so magical you should add it to milkshakes or coffee
Eat only whole carbohydrates VS Shun most carbohydrates and eat only the bare minimum of non-starchy carbohydrates
Make whole grains an integral part of your diet VS Severely limit intake of all grains VS Skip eating grains completely VS Eat no gluten at all
Enjoy legumes every day VS Never eat legumes
Potatoes are a healthy root vegetable VS Avoid eating potatoes
Eat all the fruit you want whenever you want VS Limit fruit to one or two servings a day
Eat 3 eggs every day VS Limit eggs to 6 a week VS Eat no eggs at all
Everyone with an opinion claims that their viewpoint is based on scientific support. Indeed, in these days of shared information, evidence of benefit for practically any way of eating is available to anyone who looks hard enough. The trouble is, much of this so-called scientific confirmation is not reliable or convincing either due to poorly designed studies or to studies specifically created to deliver a predetermined conclusion.
The most recent chapter of today’s story began in the US on June 15th, 2017 when a Presidential Advisory from the American Heart Association brought out new recommendations for healthy eating. Based on extensive scientific literature review, the advisory suggested that people striving for optimal health should severely cut back on all foods high in saturated fat. This includes all meats, dairy products, cheese and plant-based oils high in saturated fat (coconut oil, palm oil and palm kernel oil) and they should be replaced with whole grains, legumes and polyunsaturated fats instead of refined and processed carbohydrates (5). This recommendation was almost immediately vehemently contested beginning with an article by Kevin Michael Geary which was published on-line. His article, “Is the American Heart Association a Terrorist Organization?”, ranked the American Heart Association on a par with terrorist groups in their ability to propagate misinformation. Who is Kevin Michael Geary? It turns out that he is the founder of Rebooted Body, an affiliate marketing website for the goods and services mentioned on his website. The site offers a way to “reprogram your body for sustainable fat loss, vibrant health, & peak performance in 90 days” (6). An on-line search for the credentials of Kevin Michael Geary reveals no professional training or background in nutrition, weight loss, or psychology.
His article was picked up and reposted by other prominent figures in the great nutrition debate, notably ….
Aseem Malhotra, MD, a cardiologist in the UK, whose views on diet and health have been criticized by the British Heart Foundation as “misleading and wrong” (7). He is also the originator of the “Pioppi Diet” which, according to the British Dietetic Association, was one of the “top 5 worst celeb diets to avoid in 2018” (8)…..
…and Nina Teicholz, investigative journalist and author who in 2014 wrote “The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet”, a book that advised readers to “eat butter; drink milk whole, and feed it to the whole family. Stock up on creamy cheeses, offal, and sausage, and yes, bacon.” (9). Ms Teicholz gained a large following through this book that essentially gave readers permission to eat all the unhealthy foods that they desired. Teicholz has been deeply criticized for her views by the US Department of Health and Human Services. Marion Nestle is a professor of nutrition at New York University and Cornell University who has spent a lifetime in public education about food and its role in culture, society, and personal nutrition. She states that Teicholz’s “strong claims about the benefits of a low-carb high-fat diet go beyond what science can support” and serve only “to make nutrition science appear more controversial than it really is” rather than fostering the health of the public. Ms Teicholz has a degree in American Studies at Stanford University, and completed her masters in Latin American Studies at Oxford University. (10,11)
In spite of such hostile discord, some glimmerings of possible harmony among ideas is appearing. The year 2018 saw dietary leaders from many different versions of the best possible healthy diet coming together in constructive discussion. One of these encouraging meetings came about through an initiative of The BMJ. The BMJ (formerly known as the British Medical Journal) is a weekly peer-reviewed medical journal out of the UK that started up almost 180 years ago and is still striving, through “good science and research”, in its mission to “work towards a healthier world for all” (12). This journal, along with its partner (the Swiss Re Institute, a research and development arm of the insurance industry from Switzerland that focuses on helping people live longer and healthier lives) commissioned a series of articles to be authored by nutrition and research experts towards the goal of fostering “open and honest debate around what we know and, more importantly, what we don’t…” The articles that resulted were published in the June 2018 issue of The BMJ as “Food for Thought: The Science of Politics and Nutrition” (13). One of them brought together four authors with wildly conflicting views of nutrition and resulted in the beginning of some consensus in at least one area of nutritional controversy, the role of dietary fat in human health.
The following is a short background on these four authors.
Professor Nita Gandhi Forouhi is a researcher focused on identifying modifiable risk factors, such as the negative impact of dietary sugars and fats, with the goal of reducing the health burden of a poor diet. She heads the Nutritional Epidemiology program at the University of Cambridge in the UK. She is also Professor of Population Health and Nutrition and the leader of the Diet, Nutrition & Lifestyle Theme of the NIHR Cambridge Biomedical Research Centre (14).
Dr. Ronald M. Krauss, MD is an Endocrinologist who is the Director of Atherosclerosis Research at Children’s Hospital Oakland Research Institute. He is a well-published author in both medical journals and the lay press and his ideas have provided a foundation for the popular view that eating meat, dairy and eggs are not health hazards (15).
Gary Taubes is a journalist who gained prominence in 2002 when he wrote an article for New York Times Magazine called “What if it’s All Been a Big Fat Lie?” (16) and continued in the spotlight with his 2007 book, “Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease” (17). His publications question the health benefits of low-fat diets. In 2012 he and a colleague launched the Nutrition Science Initiative (NuSI) with the goal of solving the obesity problem, however their research has not thus far supported the dietary concepts that Mr. Taubes promotes (18,19). Mr. Taubes’ educational background includes the study of physics at Harvard University and aerospace engineering at Stanford University.
Walter C. Willett M.D. is Professor of Epidemiology and Nutrition at Harvard T.H. Chan School of Public Health and Professor of Medicine at Harvard Medical School. Dr. Willett has published over 1,700 original research papers and reviews focused on lifestyle risk factors for heart disease, cancer, and other conditions. His research and other studies have convinced him that a whole-food plant-based diet is optimal for human health. Walter Willet is said to be the most cited nutritionist internationally (20).
In their article these four authors acknowledge some of the problems that arise in the scientific investigation of the macronutrient known as fat. Dietary fat is really a complex group of nutrients with diverse effects on human health. Fats found in animal-sourced foods are generally high in saturated fat but also contain some monounsaturated and polyunsaturated fats. Similarly, fats in vegetable oils are generally not saturated but consist of mixtures of monounsaturated fats along with polyunsaturated fats which themselves contain varying concentrations of omega-3 and omega-6 fatty acids. Additionally, foods are not isolated nutrients whose benefits and detriments can be attributable to those of each existing nutrient in that food but are in actuality numerous nutrients interconnected within a food matrix with influences of its own. The resulting positive gains and negative harms from a whole food can be much greater than the simple sum of the effects of each individual nutrient. Add to these variables the effects of lifestyle, dietary choices, processing and cooking methods and socioeconomic factors and it becomes clear that the study of the health effects of fat is infinitely complicated (21).
The article then covers major problems arising from the scientific studies on dietary fat themselves. First of all, most studies don’t have enough participants nor do they follow their participants long enough to conclusively prove that alterations in fat consumption cause a reduction in the risk of chronic diseases, conditions that can take decades to manifest. In order to adequately test such a hypothesis clinical studies would require tens of thousands of participants followed for decades until endpoint conditions such as cardiovascular disease, type-2 diabetes, cancer and other chronic diseases actually appear. Additionally there needs to be a standardized definition of diet types. For example, the “low-fat diets” used in many studies often allow more than 30% of calories to come from fat whereas a true “low-fat diet” should constitute, at the very most, 20% of calories from fat. Finally, and perhaps most importantly, the identity of the nutrient replacement food used in a study is often not specified. It is imperative that the comparison food be clearly stated. Is it unsaturated fat? Is it carbohydrate and, if so, what is the quality of that carbohydrate, whole or refined? The attributes of any of these choices bring with them their own benefits or harms and will have a significant effect on the outcome of the study (21).
To sum up, the four authors present their “Key Messages” which encompass the knowledge of the role of fat in the human body that they can agree on (21):
1 For cardiovascular health, substantial evidence supports the importance of the type of fat consumed, not total fat intake, and the elimination of industrially produced trans fats.
2 Much of the evidence suggests that the risk of coronary heart disease is reduced by replacing saturated fat with polyunsaturated fats (including plant oils) but not when carbohydrate is the replacement nutrient.
3 Controversies remain about long term health effects of specific plant oils and of high fat, low carbohydrate diets, and research is needed to resolve these.
4 The focus of dietary advice must be on the consumption of foods and overall dietary patterns, not on single nutrients
In other words;
The four authors agree that intake of trans-fats and saturated fats from animal-sourced foods and certain plant oils (coconut, palm and palm kernel oils) causes increased risk of coronary heart disease. Replacement foods for these harmful fats include polyunsaturated fats. Though their discussions were confined mostly to fats they did agree that using refined carbohydrates to replace trans or saturated fats does not result in health improvement.
They point out the need for long-term clinical trials to definitively illustrate the long-term effects of high fat, low carbohydrate diets although they suggest that these sorts of studies will never be achieved due to their high costs, the necessity for very long follow-up periods and methodological problems.
They recommended that people focus on eating healthy whole foods instead of single nutrients.
While this may not seem like much of a breakthrough it is a vast improvement over the lack of communication and quarrels of the past. Surprisingly there has been virtually no backlash as a result of this article despite the fact that its message is contrary to what some of the authors and their supporters recommend.
Conflicting information about food and health can be extremely frustrating, so much so that many people admit that they simply tune out the latest nutritional news. It is to be hoped that nutritional experts from many contradictory viewpoints can work together to come to an agreement. Maybe soon the turbulence of conflict might be calmed enough to allow the creation of clear and consistent guidelines regarding dietary choices for living a healthy life and preventing chronic disease.
5 Sacks, F.M., Lichtenstein, A.H., Wu, J.H.Y., Appel, L.J., Creager, M.A., et al. Dietary Fats and Cardiovascular Disease: A Presidential Advisory from the American Heart Association. Circulation 15 June, 2017; 136(3): e1–e23.
9 Teicholz, H. The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet. Simon & Schuster; May 13, 2014; ISBN-13: 978-1483014692.
13 Bohn, J.R. (Forward). Food for Thought: The Science and Politics of Nutrition. The BMJ June 2018; 361: ISSN: 2057-0066
17 Taubes, Gary (2007). Good Calories, Bad Calories: Google Book Preview, Notes; pages 469 ff. Knopf. p. 609. ISBN 978-1-4000-3346-1.
18 Hall, K.D. A review of the carbohydrate-insulin model of obesity. Eur J Clin Nutr (Review) 2017. 71 (3): 323–326.
21 Forouhi, N.J., Krauss, R.M., Taubes, G., Willett, W. Dietary fat and cardiometabolic health: evidence,
controversies, and consensus for guidance. BMJ 361 (The Science and Politics of Nutrition): June 2018 Supp1; ISSN: 2057-0066