Biophotonic rhythms are an essential factor for human health

... synthesis depends upon UVB radiation, which effectively penetrates only the epidermal (outer) layers of the skin. Vitamin D deficiency is a current epidemic in our society today, affecting 90% of our world's population. According to vitamin D expert ...

http://www.naturalnews.com/043282_biophotonic_rhythms_sunlight_vitamin_D.html