Receptors for vitamin D are found in most of the cells in the body and research during the 1980s suggested that vitamin D contributed to a healthy immune system, promoted muscle strength, regulated the maturation process and contributed to hormone production.
During the last ten years, researchers have made a number of exciting discoveries about vitamin D. They have ascertained, for example, that vitamin D is an antioxidant that is a more effective antioxidant than vitamin E in reducing lipid peroxidation and increasing enzymes that protect against oxidation.
PCOS (Polycystic Ovarian Syndrome) has been corrected by supplementation of D and calcium.
Vitamin D plays a role in regulation of both the "infectious" immune system and the "inflammatory" immune system.
Low vitamin D is associated with several autoimmune diseases including multiple sclerosis, Sjogren's Syndrome, rheumatoid arthritis, thyroiditis and Crohn's disease.
Infertility is associated with low vitamin D. Vitamin D supports production of estrogen in men and women. PMS has been completely reversed by addition of calcium, magnesium and vitamin D. Menstrual migraine is associated with low levels of vitamin D and calcium.
Full article: http://www.westonaprice.org/basicnutrition/vitamindmiracle.html
