A closer look at a recent debate on sugars at the World Diabetes Congress

The August 2016 issue of Canadian Journal of Diabetes included two separate commentaries by Dr. Robert Lustig, MD (University of California, San Francisco, USA) and Dr. John Sievenpiper, MD, PhD (University of Toronto and St. Michael's Hospital, Canada) on the subject of sugar and diabetes. The articles summarize the points from their debate on the Health Impacts of Sugars held at the December 2015 World Diabetes Congress hosted by the International Diabetes Federation.

Lustig: Sickeningly Sweet: Does Sugar Cause Type 2 Diabetes? Yes

Sievenpiper: Sickeningly Sweet: Does Sugar Cause Chronic Disease? No

Using the diagram of the hierarchy of scientific literature, we took a closer look at the quality of sugars-related research publications that Drs. Lustig and Sievenpiper each used to reach such drastically different conclusions. 

Dr. Lustig used 1 meta-analysis of prospective cohort studies, 2 randomized controlled trials, 1 uncontrolled intervention study and 1 econometric study (based on food availability data and disease prevalence by country) related to sugars, which does not represent the highest quality or the totality of scientific evidence for his conclusion that sugar is a direct cause of type 2 diabetes.

Dr. Sievenpiper used 13 systematic reviews and meta-analyses of randomized controlled trials, and 6 systematic reviews and meta-analyses of prospective cohort studies related to sugars, in addition to other individual randomized controlled trials and cohort studies to support his conclusion that sugars is not a direct cause of chronic disease.

When reviewing the scientific literature, the hierarchy of evidence is a critical factor to consider.