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Trying to explain why “Diabetes most often begins in March,” researchers speculate about “cold weather, inactivity, and overeating.” Did they consider the possible role of a seasonal deficiency of vitamin D?

Joseph Dewhirst
Sharon, Mass.

Vitamin D would logically be at its most depleted level in the body in March and at its most concentrated level in the body in August, due to people’s sun exposure. It would be interesting to find out if cases of diabetes are less likely as people move nearer the equator. In general, the extent to which vitamin D has been ignored as an inhibitor of human diseases is astounding.

David E. Mosteller
Shreveport, La.

The study, which focused on type 2 diabetes, didn’t examine vitamin D. Studies have shown that type 1 diabetes is less common near the equator than near the poles .—B. Harder