Sexual frequency down 20 percent in 20 years (decreased vitamin D not mentioned)
Declines in Sexual Frequency among American Adults, 1989–2014
Archives of Sexual Behavior, pp 1–13
Jean M. TwengeEmail authorRyne A. ShermanBrooke E. Wells

Click here for full study online @ publisher (cannot be downloaded or printed)
Review of the study in New Y.ork Times
Possible reasons include:
1) Lower Vitamin D ==> poorer health, fatigue, pain ==> less interest in sex, exercise, etc
2) Lower Vitamin D ==> Reduced Testosterone ==> less interest in sex
This study only looked at American Adults, but suspect decreased sex around the world
See also Vitamin D Life
Fertility and Sperm category listing has items along with related searches
Testosterone levels increased after vitamin D supplementation (342 from 320) – June 2015
Incidence of 22 health problems related to vitamin D have doubled in a decade
3X increase in UK children who are vitamin D deficient in just 5 years – Nov 2015
Reasons for Vitamin D deficiency 35+ reasons
