Vitamin D Newsletter

Newsletter

Vitamin D Dosage

Robert from New Mexico writes:

Dr. Cannell: How much vitamin D should I give my children?

Dr. Cannell replies:

It depends on their pre-existing blood levels of 25-hydroxyvitamin D. ....It also depends on their genetics

 It depends on their pre-existing blood levels of 25-hydroxyvitamin D. How much sun do your children get in New Mexico? How much do they weigh? Do they use sunblock? How much milk or fish do they consume? Let me add one more thing, a stunner. It also depends on their genetics. Three twin studies—one in osteoarthritis, one is asthma, and one in multiple sclerosis—all found a significant heritability for 25(OH)D. (Heritability should not be mistaken for genetic percentage.)

The heritability of 25(OH)D levels may also explain the enormous variation in 25(OH)D response that people show when they take vitamin D. Some only show slight increases and others more robust increases in 25(OH)D, perhaps due to genetic variations in how quickly 25(OH)D is made and how quickly it is catabolized. Furthermore, Orton, et al found a significant association of 25(OH)D levels with the enzyme that activates vitamin D—which is a mystery, at least to me.

What this probably means is that how much activated vitamin D you have in any tissue of your body is under both genetic and environmental control. It varies between children, explaining why one child gets sick and the other does not. Activated vitamin D almost assuredly varies among organs as well, explaining why one vitamin D deficient-child gets asthma while another frequent infections, heart disease, rickets, diabetes, or cavities. When the vitamin D deficiency occurs in the womb, the results also vary in later life, from autism to type-1 diabetes to cancer.

Children generally need about 1,000 IU for every 25 pounds of body weight. So a 75 pound 9-year-old needs about 3,000 IU per day.

All this is simply another argument for the need for 25(OH)D testing and supplementation to the midpoint of the normal reference range. Do not accept 40 ng/mL as adequate—it is not. However, as a general rule, breast fed infants need 1,000 IU per day, bottle fed infants an extra 600 IU per day. Children generally need about 1,000 IU for every 25 pounds of body weight. So a 75 pound 9-year-old needs about 3,000 IU per day. This is in the absence of significant sun-exposure. That is, they don't need to take it in the summer if they spend time outside without sunblock. However, tremendous individual variation exists in 25(OH)D response to vitamin D.

Page last edited: 07 November 2010