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Dear Dr Cannell: Vitamin D status while breastfeeding

Posted on: November 21, 2012   by  John Cannell, MD


Dear Dr. Cannell:

I am due a baby any day now and have been supplementing with D3 throughout my pregnancy 3000 IU/day. My levels are 65ng/ml, which I am happy with. The hospital wants me to give drops to my baby but I will be breast-feeding and feel my levels are high enough for baby.

What is your opinion on this? Should I increase my daily dose?


Cynthia, Ireland

Dear Cynthia:

Please check with your doctor and see if it is 65 ng/ml or 65 nmol/l. There is a big difference. Most of the world uses nmol/l (nanomoles/liter), but the USA and a few other countries use ng/ml (nanograms/milliliter). Ireland uses nmol/l. One ng/ml is 2.5 nmol/l. So multiply ng/ml by 2.5 or divide nmol/l by 2.5 to convert to the other metric.

If you have levels of 65 ng/ml (162 nmol/l) during your pregnancy, that is almost exactly the same levels that pregnant women working outdoors in equatorial Africa have. If you maintain levels like that, your baby needs no extra vitamin D, as your breast milk will be rich in vitamin D.

However, if your level is 65 nmol/l (26 ng/ml), which I suspect is the case with your 3,000 IU dosage, your pregnancy, and the customary metric used in Ireland, then your breast milk probably will not have sufficient vitamin D to maintain adequate levels in your suckling infant. You need to either supplement the child or increase your own supplementation to 6,000 IU per day.

Levels of 65 nmol/l are lower than those seen in most humans living in the natural state, which average about 117 nmol/l or 47 ng/ml. Furthermore, controlled trials by Drs Hollis and Wagner of University of South Carolina show that higher vitamin D levels and supplementation are safe and likely healthier. While we wait the next 20 years to see how all the research turns out, the Vitamin D Council believes it is wise to maintain natural vitamin D levels. Again, those are about 50 ng/ml (125 nmol/l) in non-pregnant adults and about 60 ng/ml (150 nmol/l) in pregnant women.

We do not know what natural levels are for children, as such a study has not yet been done. However, I suspect they are also above 50 ng/ml, as children in the natural state of sun exposure have skin that is very good at making vitamin D. In fact, it would not surprise me if children in the natural state have significantly higher vitamin D levels than adults have, as I suspect children would tend to wear even fewer clothes than their parents do. In addition, many years ago Michael Holick’ s laboratory showed that young skin is twice as good at making vitamin D as is much older skin.

MacLaughlin J, Holick MF. Aging decreases the capacity of human skin to produce vitamin D3. J Clin Invest. 1985 Oct;76(4):1536-8.

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