Last week, a review published in JAMA Internal Medicine undertook an historical analysis of a set of documents related to research on sugar and its role in the etiology of heart disease. Over the past week, this report has received widespread popular media coverage. The set of documents in question consists largely of correspondence to and from the Sugar Research Foundation (SRF) during the 1960s and 1970s. According to Glantz et al., beginning in 1965, the SRF sponsored research on the relationship between sugar consumption and heart disease, and was directly involved in the direction and publication of the research.
The authors concluded that the SRF sponsored research with a pre-determined goal to downplay sugar’s role as a risk factor in heart disease. This conclusion is backed up by correspondence between sugar industry representatives and the scientists who published a 1967 review in the New England Journal of Medicine entitled “Dietary Fats, Carbohydrates and Atherosclerotic Disease.” They write: “the review concluded there was ‘no doubt’ that the only dietary intervention required to prevent coronary heart disease (CHD) was to reduce dietary cholesterol and substitute polyunsaturated fat for saturated fat in the American diet.” A main grievance with the 1967 review article is that the SRF’s sponsorship was not disclosed anywhere as a potential conflict of interest, although this was not inconsistent with research integrity standards of that time.
In the decade before this report, an increase in the rates of CHD in American men led to an increase in studies investigating the potential role of dietary factors in its etiology. At the time, multiple dietary factors were being examined, including fats, carbohydrates, protein, and excessive caloric intake, in an attempt to elucidate the single nutrient responsible for the rise of CHD in the American population. Nutrition researchers of the time took a narrow approach to their investigations, focusing on individual macronutrients, as opposed to embracing the complexity and interrelatedness of dietary factors that we acknowledge today.
By the 1960s, there were two leading scientific camps: those blaming sugar for the rise in CHD, and those blaming fat and cholesterol. Predictably, the sugar industry unilaterally supported those blaming fat and cholesterol. What was not known at the time, however, was that Ancel Keys, the major nutrition researcher pointing to fat as the sole risk factor for heart disease, had received financial support from the sugar industry as early as 1944.
Glantz et al. argue that, due in part to the influence of the SRF, blame was placed almost solely on saturated fat and dietary cholesterol as the culprits for heart disease. The 1980 USDA Dietary Guidelines for Americans similarly pointed to saturated fat and cholesterol as the main dietary factors that increase the risk of heart attack. In the USDA dietary guidelines, there is no explicit mention of sugar consumption as a factor in heart disease etiology, but rather only a warning against excess consumption in order to prevent tooth decay.
When examining the complex series of events that led to the 1980 USDA dietary guidelines, it is worth mentioning a few key caveats. First, the guidelines failed to specify what saturated fat and cholesterol could be replaced with in the American diet in order to achieve a more heart-healthy diet. Simply limiting saturated fat and cholesterol could have contributed to increased consumption of carbohydrates and refined sugars. Second, sugar intake in 1980 was much lower than recent levels, and evidence on the etiology of heart disease was as of yet inconclusive. So while still flawed, it is possible to understand the rationale behind the development of the 1980 dietary guidelines through an historical lens. It is clear that the funding role of the sugar industry should have been more transparent, and much more rigorous research into the effects of both fat and sugar intake should have been pursued. Nonetheless, the lack of emphasis on sugar is perhaps not quite as conspiratorial as a modern perspective with twenty-twenty hindsight makes it appear.
Today, the role of dietary sugar in the etiology of obesity, metabolic syndrome, and Type 2 diabetes is well established, and these factors are all known to be major risk factors for heart disease. Much to the excitement of many in the nutrition community, the 2015-2020 Dietary Guidelines for Americans, a recommended limit of no more than 10% of calories per day should come from added sugars. This new guideline change helped catalyze an update to the standard nutrition label in the next few years. Among other changes, the new label will list “added sugars” as its own subcategory.
In a recent online article, Dr. David Katz wrote that, with implication of sugar in worsening health, we must be careful not to simply replace fat with sugar in our blame: “The bottom line about diet for health is that it really does come down to the overall diet and the foods that make it up, not substituting today’s scapegoat for yesterday’s.”
The SRF is not the only member of the food industry that has historically played a heavily influential role in research and food policy. The meat and dairy industry, for example, strongly influences federal dietary guidelines. The importance of industry influence and conflict of interest disclosure cannot be overstated in food policy. One would hope that the NEJM requirement that authors disclose conflicts of interest, imposed in 1984, would prevent influence without transparency. However, it would perhaps be naive to assume the possibility of billion-dollar industries’ influence has entirely disappeared. While disclosure policies are more stringent today, the need for transparency in disclosing conflicts of interests remains pressing.
An important takeaway from the recent buzz around sugar is that we should move away from these formulations of single nutrient “scapegoats.” We should instead focus on patterns of food consumption and overall diet, instead of shaming single nutrients. Ultimately, a good diet should not be high in added sugar or saturated fat, but it should also emphasize food that is unprocessed or minimally processed.
Unfortunately, a healthy diet cannot come down to solely one ingredient, so while it is indisputably crucial to discuss and be exposed to the harms of sugar, let us not let this outrage drown out the rest of the conversation.