Infants of well-nourished mothers with adequate vitamin B12 intake do not need vitamin B12 supplements.
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It is recommended that mothers who do not eat animal proteins or who are otherwise at risk for vitamin B12 deficiency get adequate amounts of vitamin B12 during pregnancy and lactation via supplements or fortified foods.
Since vitamin B12 (cobalamin) is widely present in foods from animal sources, dietary deficiency is rare except in those eating a strict vegan diet (no fish, meat, poultry, eggs or dairy products). Most infants, children and adults in the United States get the recommended amounts of vitamin B12. If a breastfeeding mother has an adequate B12 status, her baby will receive sufficient amounts of vitamin B12 via her milk. A simple blood test can diagnose current vitamin B12 deficiency.
In the US, the DRI for vitamin B12 for adults is 2.4 µg per day, 2.6 µg during pregnancy, 2.8 µg during lactation; the DRI is proportionally less for children. The DRI has a significant margin of safety built in. Unlike other B vitamins, small amounts of vitamin B12 are stored in the liver so daily consumption is not necessary.
Who is at risk for vitamin B12 deficiency?
- Anyone who is on a strict vegetarian or vegan diet (no fish, meat, poultry, eggs or dairy products) and is not getting adequate amounts of vitamin B12 through supplements or fortified foods.
- Anyone who has had gastric bypass surgery, has pernicious anemia or has certain gastrointestinal disorders and is not getting adequate amounts of vitamin B12 through supplements or fortified foods. Some medications may also decrease absorption of vitamin B12.
- An infant born to a mother who has been a strict vegetarian or vegan for at least 3 years and who is vitamin B12 deficient herself.
- An infant born to a mother who is vitamin B12 deficient due to any other dietary or medical reason.
- An exclusively breastfed baby of a woman who is vitamin B12 deficient.
According to Nutrition During Lactation (Hamosh 1991, p. 157-58), a full-term infant of a well-nourished mother will be born with a store of vitamin B12 sufficient to meet his needs for about 8 months. If the mother is not vitamin B12 deficient herself, then her milk is an excellent source of vitamin B12 and is more than sufficient for baby’s needs through the first year.
There is evidence that babies born to vitamin B12 deficient mothers have low stores of vitamin B12 at birth. Studies have shown that mothers who are vitamin B12 deficient have low levels of vitamin B12 in their milk.
Breastfed infants may develop clinical signs of vitamin B12 deficiency before their mothers do. Vitamin B12 deficiency may develop in the breastfed infant by 2 – 6 months of age, but may not be clinically apparent until 6 – 12 months. Signs and symptoms of vitamin B12 deficiency in infants include vomiting, lethargy, anemia, failure to thrive, hypotonia (low muscle tone), and developmental delay/regression.
There have been anecdotal reports of low milk supply in vitamin B12 deficient mothers, which improved when the B12 deficiency was corrected. Mothers with pernicious anemia are also at higher risk for thyroid problems, which can affect milk supply.
For mothers who are vitamin B12 deficient, increasing vitamin B12 intake increases the amount of the vitamin in her milk.
The Vegan Diet During Pregnancy and Lactation by Reed Mangels, PhD, RD
Hamosh M, Dewey, Garza C, et al: Nutrition During Lactation. Institute of Medicine, Washington, DC; National Academy Press 1991, pp. 133-140. This book is available free from the HRSA Information Center (look under Nutrition publications).
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Institute of Medicine, Washington, DC; National Academy Press 1998, pp. 322-326. This book is available free from the HRSA Information Center (look under Nutrition publications).
General (non-lactation) information:
Dietary Supplement Fact Sheet: Vitamin B12 from the Office of Dietary Supplements, National Institutes of Health
Vitamin B-12 from the American Society for Nutritional Sciences