In the most rigorous review on sugar and weight, for instance, only five trials lasting six months or longer could be found, on a total of just 1,245 people. According to the Annals authors, this review portrayed the data as more consistent than it actually was and failed to adequately account for evidence indicating that studies in which sugar was shown to have no detrimental effect may have been suppressed from publication.
Moreover, less rigorous data from observational studies was widely found to be “inconsistent.” Sometimes sugar was associated with health problems—weight gain, Type 2 diabetes, and tooth decay—but sometimes it wasn’t.
“Overall, I would say the guidelines are not trustworthy,” Bradley Johnston, the study’s lead author and an assistant professor of clinical epidemiology and biostatistics at McMasters University told me.
The study’s finding should come as a surprise to anyone who has been avoiding sugar for years already. Sugar is a potent source of glucose, which, over time, does appear to wreak havoc on one’s metabolism and pave a direct path to obesity and diabetes. A large body of trial evidence has shown that when carbohydrate consumption is reduced, these diseases start to reverse themselves. Also, given all the recent headlines about sugar’s ill effects, from Katie Couric’s movie Fed Up to the passage of soda taxes in several cities, one could be forgiven for assuming that the evidence condemning sugar must be a done deal.
Yet here were the Annals authors saying it’s not. Reaction to the paper from nutrition experts and advocacy groups was swift, with criticism focused on the paper’s Achilles heel: It had been paid for by the International Life Sciences Institute, which receives 60 percent of its funding from 400 industry members, including some, like Coca-Cola, PepsiCo, and Mars, that very much stand to benefit from a study questioning caps on sugar.
“This is a classic example of industry-funded research aimed at one purpose and one purpose only: to cast doubt on the science linking diets high in sugars to poor health,” Marion Nestle, a prominent professor of nutrition at New York University, told National Public Radio. Dean Schillinger, the chief of the division of general internal medicine at San Francisco General Hospital, told the New York Times: “They’re hijacking the scientific process in a disingenuous way to sow doubt and jeopardize public health.”
Schillinger, with his colleague Cristin Kearns, also penned an editorial in Annals, which likened the sugar-review authors to lackeys hired by the tobacco industry to be “merchants of doubt” about the health hazards of smoking.
Industry manipulation of the science is obviously an ongoing, serious concern. It was, in part, why the editor-in-chief of Annals, Christine Laine, invited this editorial. “I wanted to show both sides of the issue,” she told me, although she said that she considered the editorial to be unusually “strident and hostile” for an academic journal. Indeed, Schillinger and Kearns both part-time advocates against sugar; they write articles and do other work for Sugar Science, a group devoted to educating the public about sugar’s health dangers. “It’s shown me that conflicts of interest are not only financial but also intellectual,” said Laine, who added disclosures about the authors’ Sugar Science affiliations to the editorial after a reader brought them to her attention, she says.