How Much Vitamin D Is Enough?

New review focuses on the many benefits of vitamin D and inadequate levels in the US.

The Mayo Clinic Proceedings has just published a review of the benefits of vitamin D. The author of this review, Dr Michael Holick, PhD, MD, not only describes the many benefits vitamin D provides, but reviews the current vitamin D status of the average American and examines the health implications of the high prevalence of vitamin D inadequacy in this country.

Vitamin D prevents rickets in children. Rickets is characterized by skeletal deformities caused by overproduction of bone and inadequate calcification of that bone. The mechanism by which this occurs was worked out through scientific experimentation and an RDI for vitamin D was established. Fortification programs were subsequently introduced in the US, essentially eliminating this vitamin deficiency disease.

Dr Holick reviews the vast body of scientific evidence that indicates that inadequate vitamin D, in addition to causing rickets, prevents children from attaining their genetically programmed peak bone mass, contributes to osteoporosis in adults and causes the painful bone disease osteomalacia.

We now know that vitamin D is involved in many other systems and diseases. Vitamin D is intimately involved in regulating gene expression for many fundamental cell functions, such as production, growth, and death. It is necessary for proper muscle function, and may help prevent diabetes, hypertension and many common cancers.

He reports that approximately 36% of otherwise healthy young adults have inadequate vitamin D levels. This percentage increases to 57% of the general medicine inpatients in the United States. There is also a high prevalence of vitamin D inadequacy in elderly patients and people with osteoporosis.

He suggests that this vitamin inadequacy is caused by infrequent exposure to sunlight, the use of sunscreens, age-related decreases in vitamin D production in the skin, and diets low in vitamin D. He concludes that supplemental doses of vitamin D and sensible sun exposure could prevent vitamin D deficiency in most of the general population.

With this knowledge, we should seriously reconsider the recommended daily intake of vitamin D. Virtually the entire population has vitamin D levels that are substantially lower than the levels that would have been present in our equatorial ancestors. We know only a small portion of the benefits of vitamin D - but we do know that supplementing vitamin D intake will provide these many benefits. Why not add more vitamin D to your wellness regimen today?

Holick, MF, High Prevalence of Vitamin D Inadequacy and Implications for Health. Mayo Clin Proc. 2006