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Supplements Help Boost Breastmilk Vitamin B12 Levels

A pregnant woman taking a tablet.
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Vitamin B12 is essential for human health, supporting the body with the synthesis of both DNA and red blood cells. In infants, it is also critical for the development of the brain.

Breast-fed infants rely solely on their mothers to provide them with many micronutrients for healthy development, which can prove difficult if women are malnourished.

In a study published in the American Journal of Clinical Nutrition, researchers from George Mason University investigated the effects of pre-natal and post-natal vitamin B12 supplementation on human milk B12 levels.

Vitamin B12 is vital for infants

Vitamin B12 is incredibly important during the first six months of an infant’s life. Deficiency in the micronutrient at this age can lead to neurodevelopmental delays and in some cases brain damage. Although rare, vitamin malabsorption can occur in exclusively breast-fed children when the mother herself is deficient, typically observed in vegans and vegetarians. Both pregnant and lactating women are vulnerable to B12 deficiency due to the toll of providing these nutrients for both themselves and their child. In countries where animal-derived diets are low, vitamin B12 deficiencies are proving to be a concern for public health.

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Using pre-natal and post-natal vitamin supplements

The research team, led by Mason Assistant Professor in the College of Public Health Dr. Dongqing Wang, investigated the optimal time and dosage for vitamin B12 supplementation in pre- and post-natal women in Tanzania.

“In resource-limited settings such as Tanzania, where maternal undernutrition is pervasive, such studies are necessary as they will contribute to the evidence base to inform the optimal timing and dosage of supplementation during pregnancy and lactation,” said Wang.


Four hundred and twelve participants were randomly assigned to receive daily oral multiple micronutrient supplementation or a placebo from recruitment (12–27 weeks of gestation) through to 6 weeks postpartum. A subset of participants were also randomly assigned to a post-natal supplement or placebo. Vitamin B12 levels in breast milk were analyzed at six weeks and seven months post-partum.

Wang and colleagues discovered that participants who took high doses of oral vitamin B12 supplements before childbirth encountered short-term benefits on the levels of B12 in their breast milk. Conversely, those who took high doses of vitamin B12 supplements postnatal experienced these benefits for a longer period of time.

“Understanding the impacts of pre-natal and post-natal vitamin B12 supplements on the level of B12 in breast milk is crucial to design effective nutritional interventions to protect mothers and infants from vitamin B12 deficiencies,” said Wang.


However, the team also observed that, in participants taking both pre-natal and post-natal vitamin supplements, the results were not as expected. When used together, the effects of supplementation on the levels of vitamin B12 in breastmilk decreased.


“It appears that there was a certain plateau in the effect when pre-natal and post-natal supplements were used together,” said Wang. “The plateau does not preclude the need for combined pre-natal and post-natal supplements through pregnancy and breastfeeding to sustain maternal B12 levels in populations with high levels of dietary inadequacy.” 


Reference: Wang D, Shahab-Ferdows S, Lweno ON, et al. The effects of prenatal and postnatal high-dose vitamin B12 supplementation on human milk vitamin B12: a randomized, double-blind, placebo-controlled trial in Tanzania. Am J Clin Nutrit. 2023:S0002916523660708. doi: 10.1016/j.ajcnut.2023.07.023

This article is a rework of a press release issued by George Mason University. Material has been edited for length and content.