Last month Professor Rebecca Mason of the University of Sydney and her co-authors wrote an excellent review of vitamin D.
Mason RS, Sequeira VB, Gordon-Thomson C. Vitamin D: the light side of sunshine. Eur J Clin Nutr. 2011 Jul 6. doi: 10.1038/ejcn.2011.105. [Epub ahead of print]
With two references, she confirmed what I always thought likely: higher calcium intake increases vitamin D levels. It makes sense, as less vitamin D is used up for absorbing calcium if calcium intake is high enough to trigger only passive calcium absorption.
I also liked her reiteration of vitamin A’s ability to interfere with the function of vitamin D, something I have written about in detail. I continue to think cod liver oil is confounding many vitamin D studies.
In several places, Professor Mason questions whether ethical concerns will mean that randomized controlled trials will never be done. After all, do you want to be randomized to the 600 IU/day control group? Not me.
I also liked her brief discussion of a wonderful paper that I wrote about last year on the study of 675 fresh cadavers. The authors compared bone biopsies and vitamin D levels of the cadavers to conclude that vitamin D levels of at least 35 ng/ml are needed for healthy bones, a study the recent FNB must have missed.
My only criticism is her failure to realize that food fortification is essential for large subgroups of the globe’s population. For example, African Americans are unlikely to seek sun exposure or take vitamin D supplements, proven by the fact that so many black women of childbearing age have vitamin D levels less than 10 ng/ml.
It appears as though some food companies are picking this up. Yesterday, Subway (the world’s largest food chain in terms of restaurant units) announced they will begin adding about 100 IU of vitamin D to the bread they use to make their subs.
Subway’s ‘Healthy’ New Bread Will Include Vitamin D, Calcium. Huffington Post, 2nd Aug 2011.
Although 100 IU is a menial amount of vitamin D, every little bit helps. And with Subway’s large and global influence, they might even help spread a little awareness.