Alternative Medicine Review 2005; 10 (2): 94–111 ~ FULL TEXT
William B. Grant, PhD, and Michael F. Holick, PhD, MD
Vitamin D sufficiency is required for optimal health. The conditions with strong evidence for a protective effect of vitamin D include several bone
diseases, muscle weakness, more than a dozen types of internal cancers, multiple sclerosis, and type 1 diabetes mellitus. There is also weaker evidence for several other diseases and conditions. There are good reasons that vitamin D sufficiency be maintained during all stages of life, from fetal development to old age. Adequate calcium intake is also recommended. The current vitamin D requirements in the United States are based on protection against bone diseases.
These guidelines are being revised upward in light of new findings, especially for soft-tissue health. The consensus of scientific understanding appears to be that vitamin D deficiency is reached for serum 25-hydroxyvitamin D (25(OH)D) levels less than 20 ng/mL (50 nmol/L), insufficiency in the range from 20-32 ng/mL, and sufficiency in the range from 33-80 ng/mL, with normal in sunny countries 54-90 ng/mL, and excess greater than 100 ng/mL. Solar ultraviolet-B (UVB) irradiation is the primary source of vitamin D for most people. In general, the health benefits accruing from moderate UV irradiation, without erythema or excess tanning, greatly outweigh the health risks, with skin pigmentation (melanin) providing much of the protection. In the absence of adequate
solar UVB irradiation due to season, latitude, or lifestyle, vitamin D can be obtained from fortified food, oily fish, vitamin D supplements, and artificial sources of UVB radiation.
There is a growing awareness that vitamin D sufficiency is required for optimal health. The role of vitamin D in calcium absorption and metabolism for
bone health is well known.  Research during the past two decades has illustrated the importance of vitamin D in reducing the risk of cancer, [2–4] multiple sclerosis, [5, 6] and type 1 diabetes mellitus.  A number of reviews on the role of vitamin D and prevention of disease and maintenance of optimal health have appeared in the past 2-3 years, [8–21] and several recent conferences have been devoted solely to exploring the role of vitamin
D in health and disease prevention. [22–24] Finally, organizations in Australia and New Zealand have recognized a sufficiently high prevalence of vitamin D
deficiency, even in these sunny lands, to have issued guidelines for solar UVB irradiation. [25, 26]
This article discusses the importance of vitamin D sufficiency at various stages of life as a guide to health practitioners, policy makers, and interested