diet wars magazine cover

A recent New York Times article about how the sugar industry manipulated research starting in 1965 is getting some attention. The article is largely based on a recent JAMA Internal Medicine article that reviews historical documents revealing how the Sugar Research Foundation (SRF) (based largely on revealed internal documents) put their thumb on the scale of diet research starting in 1965 in an attempt to shift the blame for heart disease from sugar onto fat.

The diet wars

I think this latest round of information can only be understood in the context of the longstanding diet wars. Heart disease has become the number one cause of death, as life expectancy has increased and we have reduced many other causes of mortality.

Overweight and obesity are also diseases of modern civilization which is characterized by abundance and an increasingly sedentary lifestyle. Further, the food industry is driven by market forces which favor tasty foods, which often means being high in fat and/or sugar.

The public, understandably, simply wants to know what diet is optimal for reducing cardiovascular risk and maintaining a healthy weight. Ironically, we already have the answer, in my opinion, at least the “90% answer.”

I also think that most people know the answer – engage in regular exercise and eat a moderate, varied diet with plenty of vegetables. If you do that you are most of the way to an optimal diet, and all the controversy is essentially over that last few percentage points of minimizing risk by optimizing diet.

Self-help and food industries

The people who seem to have the highest stake in those last few percent are the self-help industry and the various food industries. The self-help industry want to sell you the optimal diet, and so they have a vested interest in coming up with some diet schtick and selling it – the Atkins diet, the Zone diet, the South Beach diet, etc.

The one diet that seems to have the most science behind it is the Mediterranean diet. That is probably because it is a moderate diet, nothing extreme. Even then, a recent systematic review gave it a soft recommendation:

The limited evidence to date suggests some favourable effects on cardiovascular risk factors. More comprehensive interventions describing themselves as the Mediterranean diet may produce more beneficial effects on lipid levels than those interventions with fewer dietary components. More trials are needed to examine the impact of heterogeneity of both participants and the intervention on outcomes.

The research on diet has been controversial, allowing for ongoing multiple opinions, I think because they are playing with those last few percentage points. There simply isn’t enough of a difference to show up as a strong signal. Other differences in the participants, such as amount of exercise, weight, stress, and sleep, likely overshadow the dietary changes being studied.

A recent study comparing high fat, high sugar, and a “prudent” diet (essentially a moderate diet) also reveals this basic pattern of not seeing much difference. They looked at all-cause mortality, heart deaths and heart events. The high fat diet was associated with increased overall mortality, but not heart deaths or events. The high sugar diet was associated with a borderline but not significant trend toward higher heart deaths and events but not overall deaths. The prudent diet had no increased risk.

There are also various food industries that would love for the research to show that the food they produce is the healthiest – for example, the sugar industry, the dairy industry, and the meat industry. All these industries fund research hoping to show that their product is healthful.

Sugar industry tampering

The recent NYT article and the JAMA article on which it is based detail how the SRF engaged in a clever campaign, not so much to exonerate refined sugar, but to shift the focus onto fat. They funded research, provided papers for review, and participated in reviews that emphasized saturated fat and cholesterol as primary cardiovascular risk factors.

There is nothing necessarily wrong with industry funding research. This is pretty much a necessity as the amount of research that can be funded with public dollars is limited. Over the years, however, standards have emerged to mitigate the problem of bias in industry-funded research.

These standards include total transparency. Researchers have to reveal the source of their funding and any potential conflicts of interest, including ties to industry. Journals also have to reveal industry ties. Human trials also have to be registered, so industry cannot later hide them if they don’t like the results. Further, reviewers are encouraged to weigh independent research more heavily than industry funded research.

This is a bit of an ongoing game of cat and mouse, where industry tries to find ways to put their thumb on the scale, and the scientific community tries to stop them. Vigilance is required, and exposés like the JAMA article are all part of the picture.

However, I think the NYT article failed to put this episode into the full context of the diet wars over the last 50 years. Scott Alexander wrote an article making the same point.

The dairy industry and meat industry also funded research over this time. It is actually not clear what the net effect of industry research was. Further, the research is complex. Researchers are looking for what I think is a small signal and there are many ways to conduct research and look at the data.

In the end I think it’s clear that eating too much sugar and eating too much fat are both risk factors for obesity and heart disease. Again – moderation is the answer.

Bottom line for the consumer

Despite all the complexity in the research, the many factions pushing their special diet, and those trying to exonerate the food they produce or point the finger at a competitor, we are back to a simple recommendation – eat a varied moderate diet with plenty of vegetables and exercise regularly.

I always have to add the caveat that for those with medical conditions, like diabetes, they may need to eat a modified diet with another layer of complexity. Some people may also have specific nutrient deficits. But for most people, the above advice is really all they need to know.

Further, there is no magic optimal food, or bad food to avoid, or “zone” of balance of macronutrients, or superfood, or special diet that will have a significant positive impact on your health. In fact, such diets can be a net negative when they deviate from a moderate diet with extreme recommendations. Special diet tricks and supplements also will not compensate for an overall bad diet or lifestyle.

People sometimes lose the 90% benefit of a moderate diet while pursuing an apparent few percentage points of advantage from a special diet.

What this episode also reveals, and is something that I think most people already know, is that you should not believe marketing hype. Foods plastered with labels that they are “all natural,” “low fat,” “low sugar,” “organic,” “clean,” “free of something,” or whatever will not benefit your health. These are nothing but marketing ploys.

(Oh, and whatever you do, don’t listen to celebrities or take advice from People magazine.)


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.