Some Data on Vitamin D Supplementation

Vitamin D has been known to be involved in many physiologic functions and vitamin D deficiency can cause a whole spectrum of diseases, including heart disease, diabetes and cancer.

For people who do not get exposed to sunlight professionally, a supplementation of 4000 to 6000 IUs of vitamin D is recommended by the most knowledgeable experts on this vitamin.

However many people are worried about the safety of vitamin D used at this level because this dosage is more than 20 times higher than the Adequate Intake for vitamin D recommended by the Institute of Medicine.

The Food and Nutrition Board of the Institute of Medicine in 1997 recommended that the adequate intake for vitamin D is 5 mcg (200 IU) per day for all people under the age of 50 inclusive. For those who are between 51 and 70, 10 mcg or 400 IUs is recommended.  For adults at the age of 71 or older, 15 mcg or 600 IU per day are recommended.  The Institute does not recommend that pregnant women and breastfeeding mother, regardless of their ages, increase their intake of vitamin D. That is, they recommend 5 mcg or 200 IU per day. These "adequate intakes" are believed by the Institute to maintain serum 25(OH)D levels of at least 37.5 nmol/L or 15 ng/ML, according to Linus Pauling Institute.  These recommendations have drawn criticism from vitamin D experts.

In a comment published in the May 1999 issue of American Journal of Clinical Nutrition, Dr. Vieth R, one of most knowledgeable experts on vitamin D and diseases, says that 5 mcg or 200 IU per day of vitamin D may prevent osteomalacia in the absence of sunlight, but not enough to help prevent osteoporosis and secondary hyperparathyroidism. Dr. Vieth is a professor at the University of Toronto in Canada.

The known adverse effect associated with vitamin D supplementation is hypercalcemia.  But Dr. Vieth says published cases of vitamin D toxicity with hypercalcemia all involve intake of > or = 1000 microg (40000 IU) per day.

Those who are worried should remember that exposure to sunlight can get them 250 microg (10000 IU) vitamin D per day.

Dr. John Cannell, a vitamin D expert and director of Vitamin D Council suggests the following on his website:

If you use suntan parlors once a week or if you live in Florida and sunbathe once a week, year-round, do nothing. However, if you have little UVB exposure, my advice is as follows: healthy children under the age of 1 years should take 1,000 IU per day - over the age of 1, 1,000 IU per every 25 pounds of body weight per day. Well adults and adolescents should take 5,000 IU per day. Two months later have a 25-hydroxyvitamin D blood test, either through ZRT or your doctor.

Dr. Cannell suggests that one needs to maintain 50 to 80 ng/ml to fight diseases.

By David Liu and editing by Rachel Stockton