Seriously? That Sandwich Might Give You Type 2 Diabetes?
From time to time, nutritional epidemiologists take themselves entirely too seriously. This week is one of those times. Health reporting is full of warnings that your lunch sandwich might give you type 2 diabetes. The senior author of the paper in Lancet Diabetes and Endocrinology causing this stir, Professor Nita Forouhi, expresses no caution about confusing correlation with causation when she tells the Guardian:
“Our research provides the most comprehensive evidence to date of an association between eating processed meat and unprocessed red meat and a higher future risk of type 2 diabetes. It supports recommendations to limit the consumption of processed meat and unprocessed red meat to reduce type 2 diabetes cases in the population.”
A Small Effect Size
But hang on, what was the effect size in this study of associations across a massive sample size? A mere 15%. In other words, people who ate a serving of processed meat every day were only 15% more likely to coincidentally develop type 2 diabetes later in life.
We find ourselves wondering if the dullness of a life filled with a bologna sandwich for lunch every day might account for the elevated risk of diabetes. That’s called residual confounding and the possibilities for it are infinite in a study like this. But we digress.
For perspective, it’s worth pausing for a moment to consider the factors that have an effect on diabetes risk. Smoking, for example, has an association with a 30-40% higher risk of diabetes – more than twice the effect size in the lunch meat study du jour. Physical inactivity correlates with twice the risk of developing type 2 diabetes. The association of obesity with diabetes risk is a six-fold increase.
And as new data reminded us this week, treating obesity can do a whole lot to reduce a person’s risk of diabetes.
A Weak Case
In context, this correlation between processed meat and diabetes risk is trivial – even if the argument for causality were clearer than it is. There are much better reasons for reducing excessive processed meat consumption. Risk of cardiovascular disease is a good one.
So no, that sandwich you had for lunch today is not likely to give you diabetes.
Click here for the new study and here for some thoughtful reporting on it.
Coffee and Sandwich, photograph by Geoff Peters, licensed under CC BY 2.0
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August 22, 2024
