Do non-diabetics need to monitor their glucose?
Continuous glucose monitoring (CGM) is essential diabetics: approximately 9 million people depend on it for daily diabetes management around the world. Track glucose at home means diabetics know how their blood sugar responds to meals—their postprandial glycemic response (PPGR).
CGM devices have become increasingly popular with non-diabetics in recent years. The biohacking community latched onto them as a way to continuously track blood sugar in their quest for optimal (and long-term) health. One CGM subscription service, Levels, promises to help you identify an “ideal diet,” as well as “smart swaps for more stable glucose.” Their service also offers “comprehensive blood tests” to offer even more AI-powered nutrition advice.
Does this science hold up, however?
A new editorial, published in The American Journal of Clinical Nutrition, questions the efficacy and necessity of such constant monitoring for non-diabetics.
A highly variable product
The main issue lies in the day-to-day variability of an individual's blood sugar responses, or intraindividual variation (iiV). This variability is significant enough to cast doubt on the accuracy of using CGM for personalized nutrition advice, writes Thomas Wolever, professor emeritus in the Department of Nutritional Sciences at the University of Toronto.
Here are his key findings:
The variability in blood sugar responses can be quite large, with coefficients of variation ranging from 14% to 40%
This variability differs based on factors such as diabetes status, what exactly is being measured, and the method used to analyze glucose levels
One recent study found that the variability in blood sugar responses was so high that it could lead to incorrect rankings of how different foods affect blood sugar levels
The authors of that study write:
Individual postprandial CGM responses to duplicate meals were highly variable in adults without diabetes. Personalized diet advice on the basis of CGM measurements requires more reliable methods involving aggregated repeated measurements.
Wolever notes what this high variability in non-diabetics means for personalized nutrition:
A single CGM test may not accurately predict how a food will affect an individual’s blood sugar
To be confident in the rankings of how different foods affect blood sugar, multiple tests (potentially dozens) would need to be conducted for each food
An obsessive tracking of food intake can result in an eating disorder known as orthorexia, as I wrote in Teen Vogue earlier this year. While tracking health status and having goals is important, there’s always the possibility of mental and emotional health issues arising from food anxiety.
Orthorexia is especially challenging to diagnose since biohacking predominantly appeals to men, and men are less likely to admit to experiencing eating disorders. Such disorders are also harder to physically identify with men, since historically EDs present in women as an obsession with thinness while men often focus on bulking up—a socially sanctioned sign of “true health.”
Orthorexia a disorder in which people continually eliminate foods from their diet due to purity or health reasons. If a CGM causes people to eliminate foods due to high variability, they could be removing necessary nutrients from their diet.
Some critics argue that non-diabetics can maintain tight blood glucose regulation without monitoring. And since CGMs only measure glucose in the interstitial fluid between skin layers, and not the more reliable method finger prick method which measures blood in the bloodstream, accuracy remains an issue.
The irony: in their quest for optimal health, CGMs could make non-diabetics less healthy.
