How a mother’s Vitamin D status influences her breastmilk levels

Nothing in the human body works in isolation. Vitamin D helps regulate the amount of calcium and phosphate in our body and is needed to keep our bones, teeth and muscles healthy.

As it’s essential for calcium absorption in the body, in a relatively small number of cases its deficiency can also lead to rickets in children. It’s been reported worldwide that there’s been a recent re-emergence of Vitamin D deficiency (VDD) and rickets among breastfed babies - without adequate sunlight exposure and Vitamin D supplementation.

It makes sense that breastfeeding mothers with a Vitamin D deficiency themselves would have a reduced amount of Vitamin D in their breastmilk, resulting in Vitamin D deficiency in their breastfed baby. This prevalence of Vitamin D deficiency in breastfed babies differs vastly between studies and nations at 0.6% - 91.1%!

Breastfed babies are (can be) ‘particularly vulnerable’ because breastmilk doesn’t naturally contain high levels of Vitamin D. Combine this with a mother having low Vitamin D levels herself, it further reduces the amount that passes through breastmilk.

Then add in less sunlight exposure (and overuse of sunscreens), limited natural dietary sources of the other fat-soluble vitamins (A, K) foods (egg yolk, beef liver, oily fish), magnesium and zinc.

There is now a movement (via international guidelines) to “give breastfed babies a Vitamin D supplement of 400 IU/day during the 1st year of life”.

Yet research shows that high-dose maternal vitamin D supplementation (eg. 4000-6400 IU/day) “can enrich breastmilk adequately for babies.”

So why aren’t pregnant women given this information?

100% of the pregnant mothers I work with would rather ensure their Vitamin D levels are optimal throughout their pregnancy than give their babies an oral Vitamin D supplement every day for their first year of life!

Maternal Vitamin D levels really should be tested before pregnancy (if possible), then once in each trimester.

As a Naturopath I like levels to be around 120nmol/L throughout pregnancy. I find women getting pregnant towards the end of winter will often need additional supplementation as their stores have dropped over the season. Plus, having adequate Vitamin D in pregnancy also lowers rates of gestational diabetes!

If a mother’s level is very low, I often use a calcifediol form of Vitamin D supplement for its potency and bioavailability. This works to raise levels quickly in the body. I then support the maintenance of healthy levels using a cholecalciferol form of Vitamin D, alongside healthy doses of sunlight and dietary sources.

Being proactive in the preconception phase, or at the very least throughout pregnancy can support healthy maternal Vitamin D levels. This in turn, enriches a mother’s breastmilk for their baby, reducing the need for supplementing baby directly.