A new PLoS ONE twin study on the seasonal genetic influence on serum 25-hydroxyvitamin D levels finds
Half of the variability in 25-hydroxyvitamin D during the summer season was attributed to genetic factors. In contrast, the winter season variation was largely attributable to shared environmental influences (72%; 95% CI 48-86%), i.e., solar altitude.
The authors have probably missed our earlier communication in the Lancet. Although our heritability estimates were somewht higher we arrived at the same unexpected conclusion. Here comes the plot that the Lancet stripped from our letter in 2006.
It may be one of the very first example of gene effects that only come into play when the system is under heavy load, yea, yea.