02:05am Wednesday 18 October 2017

Conflicts of financial interests can bias scientific analyses when linking sugar-sweetened drinks and obesity

Ms. Maira Bes-Rastrollo, from the Preventive Medicine and Public Health Department, prime author of the research which was led by Miguel Ángel Martínez-González, stated that it is five times more likely that those systematic reviews where their authors admit the existence on their part of a potential conflict of financial interests, point to links between consumption of soft drinks and weight gain being inconclusive, in comparison to those reviews that do not have conflict of interests.

Systematic reviews identify, analyse and summarise all the research available on a topic. They use standardised methodology in order to be thoroughgoing and minimise possible bias, and are commonly used when drawing up health policies as being the best available data. In this research, which likewise used systematic review methods, researchers identified 17 published systematic reviews that had evaluated links between the consumption of soft drinks with weight gain and obesity. In six of these, the authors declared themselves as being affiliated to or receiving funding from the food and drinks industry.

Opposing results

The researchers found that, while 83.3% of “clean” systematic reviews (with no conflict of interest) concluded that consuming soft drinks was a potential risk for weight gain, 83% of the reviews in which the authors admitted links with the industry gave the result that the scientific evidence for associating such consumption with weight increase was insufficient. “These findings, underlined Ms. -Rastrollo, increase concern about the exactitude of the results from research financed by the food and drinks industry, although it is true that this research cannot evaluate which available interpretation is correct. In any case, this concern is supported by random and controlled trials amongst both children and adults, and in which a risk association between the consumption of soft drinks and weight gain was observed”.

The researchers from the University of Navarra point out that “for authors stating they do not have a conflict of interest, systematic reviews financed by the drinks or sugar industry normally express a lack of association between consumption of soft drinks and obesity, giving rise to contradictory results on comparing them with the original studies included in the systematic review”. They continued: “Our findings help to call attention to possible errors present in the scientific evidence from food industry-funded research”.

The German Institute for Human Nutrition also cooperated in this research.

Dietetika/Elikagaiak, Ekonomia, Osasuna, Unibertsitateak 

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