Saturday, March 02, 2013

Sugar! The Relationship of Sugar to Population-Level Diabetes Prevalence: An Econometric Analysis of Repeated Cross-Sectional Data

A little bit of sugar reduction helps the (diabetes) medicine go down. 

Over at the New York Times, nutrition writer Mark Bittman has just reported on an extensive statistical study which suggests a stand-alone relationship between sugar and diabetes. The study is published in full on PLOS ONE. It is wide in scope and has been well-conducted, with one of the authors (Sanjay Basu) writing a nice supplementary blog piece on understanding the data, methods and findings. I view this kind of study as interesting because it isn't ground breaking but ground building. It's the type of work that helps steer our understanding toward somewhere new. 

From the abstract conclusion:

"No other food types yielded significant individual associations with diabetes prevalence after controlling for obesity and other confounders. The impact of sugar on diabetes was independent of sedentary behavior and alcohol use, and the effect was modified but not confounded by obesity or overweight. Duration and degree of sugar exposure correlated significantly with diabetes prevalence in a dose-dependent manner, while declines in sugar exposure correlated with significant subsequent declines in diabetes rates independently of other socioeconomic, dietary and obesity prevalence changes. Differences in sugar availability statistically explain variations in diabetes prevalence rates at a population level that are not explained by physical activity, overweight or obesity."

Adjusted association of sugar availability (kcal/person/day) with diabetes prevalence (% adults 20–79 years old). Regression line is adjusted for all control variables, including time-trends (period-effects)
On the extent of the effect, the authors write:

"a 150 kilocalories/person/day rise in sugar availability (one 12 oz. can of soft drink) was associated with a 1.1% rise in diabetes prevalence"

It's a shame about those really high 5-6 points on the chart that are clustered together just on the sugar reduction side of the scale. Nevertheless, an upward sloping line is evident.

On his blog, Sanjay Basu concludes:

"The bottom line is that this is one of several studies from independent scientific groups that have questioned the old mantra that “a calorie is a calorie”. Some calories may be more metabolically harmful than others, and sugar calories appear to have remarkably potent properties that make us concerned about their long-term metabolic effects. This study also suggests that obesity alone may not be the only issue in diabetes pathogenesis. The study was conducted to understand a statistical theory, using a statistical approach. It doesn’t say anything about any specific person’s diabetes risk or provide any kind of dietary advice. This data cannot distinguish between types of sugars (like high fructose corn syrup versus other types of sugars), nor does it establish more insight into the mechanisms that are at play, which need to be pieced together in laboratory and experimental research studies."

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