Vitamin D Newsletter


Should I Supplement With Vitamin A?

John from California writes:

Dr. Cannell:

Are you saying no vitamin A at all or just not too much of a good thing?

Dr. Cannell replies:

No extra vitamin A unless you have a bowel disease that impairs absorption of vegetables and transportation of carotenoids. The paper referenced at the end of this paragraph discusses how Americans are getting too much of a good thing. Vitamin A is like vitamin D, it has a U-shaped curve, too much or too little will harm you. Too much is the rule, not too little, in developed countries. Furthermore, it gives a mechanism by which excessive doses of vitamin A will impair brain development and, although I can't put my finger on the reference right now, at least one author has proposed that excessive vitamin A intake may worsen autism. The vitamin D theory of autism would predict just that.

Page last edited: 16 June 2011