The chart below demonstrates the profound influence that season can have on vitamin D levels and risk of deficiency. During the summertime, for example, there is a 70% decreased risk of vitamin D deficiency compared to the winter time.

This chart was created from data presented in a 2008 paper from Melamed et al., 25-hydroxyl Vitamin D Levels and the Risk of Mortality in the General Population. The researchers analyzed vitamin D levels and mortality using health data of 13,331 adults from the National Health and Examination Survey (NHANES) III (1988 – 1994).

gorham deficiency by season

Seasonal trends have been observed in several diseases.  In an effort to maintain a target serum level of 40-60 ng/ml (100-150 nmol/L) throughout the year, GrassrootsHealth recommends measuring the vitamin D serum level at the end of summer (October) and at the end of winter (March), and adjusting intake or vitamin D routine accordingly.


25-hydroxyl Vitamin D Levels and the Risk of Mortality in the General Population

Michal Melamed et al.

Archives of Internal Medicine

August 2008

Read Paper

Vitamin D Deficient - Hispanic Couple Smiles

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