Breast milk: not enough vitamin D3 in it

Although it is considered a "perfect" food, breast milk does not contain sufficient amounts of vitamin D. Therefore, exclusively breastfed infants are at risk of deficiency, especially if they are not adequately exposed to the sun. A new study reveals that taking far higher than recommended doses of vitamin D during the breastfeeding period allows new mothers to avert the risk of vitamin D deficiency and provides a viable alternative to direct infant supplementation.

This is according to a study conducted by researchers at the Medical University of South Carolina (USA) and published in the journal Pediatrics.

Breast milk does not contain enough vitamin D

Colostrum, the milk produced during the first few days of lactation, is particularly rich in nutrients needed by the infant. The nutritional content of breast milk then continues to change during the course of lactation and is highly variable from woman to woman. Although it is considered a "perfect" food, breast milk does not contain sufficient amounts of vitamin D to maintain the proper level of 25-hydroxy-vitamin D, an intermediate of the biologically active form, in infants. 

Therefore, exclusively breastfed infants are at risk of deficiency, especially if they are not exposed to the sun, which is known to stimulate the production of vitamin D in the skin from one of its precursor molecules. It seems, moreover, that children belonging to some ethnic groups with dark skin are particularly prone to this deficiency. 

Vitamin D is valuable for bone health and therefore essential for preventing rickets, and it is essential for the proper development of the infant's skeleton. To fully meet infant needs for vitamin D, supplements can be given directly to the infant or maternal supplementation can be used and vitamin D content in milk can be increased.

Supplementation with 6400 IU vitamin D prevents deficiency in breast milk

In the study, the researchers compared the effectiveness of maternal supplementation with 160 micrograms per day, and maternal and infant supplementation with much lower doses of vitamin D. The data obtained showed that the higher amount was able to ensure the optimal amount of vitamin D for the infant during breastfeeding. 

Going into detail, the analyses conducted showed that mothers who had received 400 International Units (IUs) of vitamin D, equivalent to 10 micrograms, or 2400 IUs (60 micrograms), were more likely to be deficient in the vitamin than those who had received 6,400 IUs, an amount equal to 160 micrograms. In addition, during breastfeeding, blood concentrations of 25-hydroxy-vitamin D had decreased in the women who had received 400 IU, while they had increased in the group of mothers who had taken the highest dose. 

After the first month of life, more than 70 percent of the infants had vitamin D concentrations below the recommended level (50 nanomoles per liter). One of the most important findings was to observe that blood vitamin D concentrations were similar between breastfed infants whose mother had consumed 6400 IU per day of vitamin D, and those who had directly received 400 IU orally.

Some highlights of the research

The women involved in this study, 334 paired with their children, were selected from 2 distinct latitudes of America with such strong diversity among ethnicities that the results can be generalized to a wide range of mothers. In addition, the doses of vitamin D used in this study caused no side effects and are considered safe by the authors of the research, as no adverse effects are known. 

In this regard, the IOM (Institute of Medicine) the academic association that offers health advice and counseling, has increased the limit to 4,000 IU per day, and the Endocrine Society (an international homone research society) has set the upper limit at 10,000 IU per day.

Moms should take more vitamin D

This study points out that the amounts of vitamin D taken in by mothers and exposure to sunlight are often insufficient, and as a result the composition of breast milk may not provide the optimal amount to infants. 

As is the case with omega-3: low consumption of fatty fish in pregnancy can cause a deficiency in human milk of fatty acids that are important for the child's development. Adequate vitamin D consumption and supplements can, therefore, ensure that lactating women have optimal levels of the vitamin in their milk and thus in their babies. To stay up-to-date on the latest news from scientific research on Omega-3, subscribe to our newsletter. 

Sources: Hollis BW, Wagner CL, Howard CR, Ebeling M, Shary JR, Smith PG, Taylor SN, Morella K, Lawrence RA, Hulsey TC. Maternal vs infant vitamin D supplementation during lactation: A randomized controlled trial. 2015 Pediatrics. Luzwolda MF, Kuipers RS, Koops J-H, Muller S, de Graaf D, Dijck-Brouwer DAJ, Muskiet FAJ. Interrelationships between maternal DHA in erythrocytes, milk and adipose tissue. Is 1 wt% DHA the optimal human milk content? Data from four Tanzanian tribes differing in lifetime stable intakes of fish. 2013 Br J Nutr.