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Sugar isn´t sweet: Junk Science or Junk Food?

Comment by Uwe Nixdorff, EAPC Secretary

Diabetes and the Heart

 It is evidence that a diet rich in carbohydrates with a high glycaemic index resembles relevant cardiovascular risk mainly by being the pathophysiologic background of the deleterious effects of the metabolic syndrome. Representative of high glycaemic carbohydrate is glucose, not only being the content of sweets and soft drinks but also processed within various ready to go dishes for quick cookery. Insulin is stimulated to high extents, consecutively decreasing as fast as originated which induced hunger for the next sugar nutrition and the vicious circle for overweight and obesity is initiated. Also AGE = advanced glycogenated end products are known to have direkt effect on endothelium and vessel walls stimulating the atherosclerotic process.

The 2016 European Guidelines on cardiovascular disease prevention in clinical practice clearly summarizes in so far that “regular consumption of soft drinks has been associated with overweight, metabolic syndrome and type 2 DM. … sugar-sweetened beverages was associated with a 35% higher risk of CAD in women, …” (1).

Thus, in contrast to this acknowledgement a recent systematic review on guidelines on sugar intake ended up with the conclusion that the quality of evidence for any recommendation on dietary sugar is low to very low (2). The aim of this review has been to assess consistency of recommendations in guideline papers on sugar intake, look for methodological quality of those guidelines, and the quality of evidence supporting each recommendation. MEDLINE, EMBASE, and Web of Science have been the basis for data sources, published between 1995 and 2016. Instruments for this have been the “Appraisal of Guidelines for Research and Evaluation (AGREE II)” as well as “Grading of Recommendations Assessment, Development and Evaluation (GRADE)” methods. Nine guidelines offering 12 recommendations have been found. Guidelines scored poorly on AGREE II criteria, specifically in rigor of development, applicability, and editorial independence. Recommendations were based on nutrient displacement, dental caries, and weight gain.

Conclusions have been that common Guidelines on dietary sugar do not meet criteria for trustworthy recommendations and are based on low-quality evidence. Furthermore this is followed by the statement that “public health officials (when promulgating these recommendations) and their public audience (when considering dietary behavior) should be aware of these limitations”.

In my personal opinion those kinds of oecotrophologic studies underlying those guidelines are always problematic because even in prospective studies it is very hard to control for confounders. However, furthermore there has been an Editorial by Schillinger (3) pointing out further critical remarks, especially the bias of industry support. He has published another paper in which he concludes that studies are more likely to conclude on no relationship between sugar consumption and health outcomes when investigators receive financial support from the food and beverage (F&B) industry (4).

He has some concerns of selecting papers which might be biased as well as AGREE II which in principal is limited to practice guidelines in the treatment of illness. At least, the editorial author believes that this review is an example of the “politicization of science” (5).

At least the disputable review paper has been followed by press reactions, for instance by The New York Times by the heading “Study Tied to Food Industry Tries to Discredit Sugar Guidelines” pointing out quick elicited sharp criticism because the authors have ties to food and sugar industries. Looking back to the original paper discloses indeed those financial support and disclosures. Especially the International Life Sciences Institute paid into this work, funded by multinational food and agrochemical companies including Coca-Cola, Mars, Nestlé, General Mills, Hershey´s, Kellogg`s; Kraft Foods and Monsanto. Barry Popkins, a professor of nutrition at the University of North Carolina at Chapel Hill, has been quoted by The Times, who has been stunned that the paper has been published at all because its authors “ignored the hundreds of randomized controlled trials that have documented the harms of sugar.

Just to underline the official recommendations of the WHO from 1989 as well as the WHO/FAO (Food and Agriculture Organization of the United Nations) from 2002 the healthy proportion of sugar intake should be less than 10% of calories (6)
Notably, may be even more paradoxically, biased publications tried to neglect the harmful effect of smoking as well as passive smoking on the cardiovascular system (7)
This “systematic” review should remind us as well as editorial boards of journals to always recognize any disclosure which is also meanwhile a correct requisite of any lecture at any ESC meeting as well as publication.

Note: The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology