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Birth weight associated with vitamin D levels

Posted on: December 5, 2011   by  John Cannell, MD


Ask yourself, during the 2 million years of our evolution into humans in equatorial Africa, what kind of babies would the women have? Remember, it was late in our evolution when we became top predator. For most of our evolution, we were eating bugs, roots, and plants, prey to tigers and the like, not killing and eating mastodons. In fact, when we began killing and eating mastodons, our genome likely had already evolved. What kind of babies did we have before we were eating mastodon pancreas?

One thing the baby would have to be is quiet. With predators all around, a whining, crying baby would endanger the entire tribe. I suspect the headman would quickly dispatch a loud infant. Of course, the mothers, who were naked in equatorial Africa, and who never washed (Holmes proved some vitamin D production occurs on the surface of the skin), would have high vitamin D levels, so their breast milk would also have high vitamin D levels, unless nature decided such infants were supposed to sunbathe and attract the eyes and noses of predators. No, I suspect newborns were hidden away, out of the sunlight and getting their vitamin D from nature’s perfect food: the breast milk of vitamin D sufficient women.

What else would Paliolithic (the period when humans became humans, about 2 million to 15,000 years ago) infants need to do? They would need to be born fast. Can you imagine a 10-hour labor? The entire tribe would be in jeopardy. No, these infants had to be born quickly and quietly, like so many prey mammals do today. In order to avoid prolonged labors, the infants would have to be born quite small.

This brings us to Professor Lisa Bodnar’s and colleague’s paper from the University of Pittsburg that has bothered me since I read it last year (I love papers that bother me and make me think). It is free to download in its entirety:

Bodnar LM, Catov JM, Zmuda JM, Cooper ME, Parrott MS, Roberts JM, Marazita ML, Simhan HN. Maternal serum 25-hydroxyvitamin D concentrations are associated with small-for-gestational age births in white women. J Nutr. 2010 May;140(5):999-1006.

On page 1004, you will find the graph that bothers me. A “U shaped curve,” showing lower birth weights with both low and high vitamin D levels. Small for gestational age or SGA, is a category that includes constitutionally small babies and pathologically small babies. Actually, when I asked a number of women, they didn’t seemed to mind having small babies; it sounded like more fun and less work to them.

The first thing to think about is that at 40 ng/ml, breast milk starts to have large quantities of vitamin D in it. Therefore, the mothers who had the best breast milk had babies that were too small and thus unhealthy. I doubt that. Professor Bruce Hollis and Carole Wagner were the ones who discovered normal breast milk is loaded with vitamin D; the problem is that 95% of pregnant women are not “normal.”

Second, I understand why a baby whose mother has a vitamin D level of 10 ng/ml will have an SGA baby; those babies don’t have enough vitamin D to develop properly. When you get to 75 nmol/l (30 ng/ml), the babies are the biggest but the vitamin D levels are still unnaturally low. Biggest is not always best. Levels of 30 ng/ml may mean a prolonged and painful labor, due to a large baby, putting the woman and the entire tribe at risk.

What size babies do the women have with natural vitamin D levels (around 50 ng/ml)? Dr. Bodnar’s data shows they have small babies, probably quickly born due to their small size, and, I guess, quiet and alert. I have only seen three babies born to women who took 5,000 IU throughout pregnancy, and they were all small, quiet, and alert. Moreover, tigers ate not one of them.

1 Response to Birth weight associated with vitamin D levels

  1. Rebecca Oshiro

    Thank you for this absolutely fascinating piece. I’ll be sharing this with my pregnant friends.

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