Vitamin B-12 Deficiency and Breastfeeding

by Anne Eglash MD, IBCLC, FABM

Can infants become vitamin B-12 deficient while exclusively breastfeeding? The vitamin B-12 level in breastmilk depends on a normal maternal vitamin B-12 level. If a breastfeeding mother has a low B-12 level, her infant will not receive sufficient vitamin B-12 through breastmilk. A breastfeeding mother may be deficient in vitamin B-12 for several reasons. Her diet may be low in B-12, particularly if she is a vegan, or if she has a nutritionally poor diet. Many individuals have trouble absorbing vitamin B-12, such as those with a history of gastric bypass, intestinal surgery, ongoing intestinal inflammation, celiac sprue, or pernicious anemia. Certain medications inhibit vitamin B-12 absorption, especially metformin.

Fetuses store vitamin B-12 in their livers, and these vitamin B-12 stores will often provide sufficient B-12 until about 4 months of age. At that point, if the breastmilk is low in B-12, the infant will start to display symptoms of vitamin B-12 deficiency.

The article for this week’s Clinical Question of the Week highlights a case of an infant who had several illness symptoms, and eventually was found to be vitamin B-12 deficient.

What do you think are infant signs and symptoms of low vitamin B-12, according to the authors of this article? Choose one or more:

Weakness
Recurrent infections
Anemia
Low muscle tone
Failure to thrive
Bald, smooth tongue

See the Answer

The answer is all of the above

Read the Abstract

Frequent Infections, Hypotonia, and Anemia in a Breastfed Infant

Kamoun F1, Guirat R, Megdich F, Ben Ameur S, Kallel C, Hachicha M. J Pediatr Hematol Oncol. 2017

Vitamin B12 deficiency may be responsible of serious hematologic and neurodevelopmental abnormalities. We report the case of an infant who was hospitalized because of recurrent infections, failure to thrive, hypotonia, and weakness. He was 8 months old and had been exclusively breastfed. Blood cell count showed pancytopenia with megaloblastic bone marrow. The serum IgG concentration was low. Vitamin B12 level was very low and associated with increased urinary methylmalonic acid. Cobalamin deficiency was caused by mother’s unrecognized pernicious anemia. Vitamin B12 supply led to rapid clinical and hematologic improvement.

Milk Mob Comment by Anne Eglash MD, IBCLC, FABM

Lactation specialists need to consider the possibility of vitamin B-12 deficiency when managing a breastfeeding infant who appears weak at the breast, low tone, and is not gaining weight well.

In fact, in the initial evaluation of a breastfeeding dyad, asking about maternal diet as part of her medical and social history would help to identify the possibility of a vitamin B-12 deficiency for the mother and infant. It would be reasonable to check a vitamin B-12 level in a mother who has a history of gastric bypass, intestinal inflammation, chronic anemia, veganism, metformin use, or an admittedly terrible diet (ie living on chips, donuts, candy, etc). Identifying pernicious anemia, which is an autoimmune disease causing inability to absorb B-12 adequately, would be difficult to diagnose, unless the mother has symptoms of a low B12, such as a sore tongue, fatigue, and numbness/tingling of fingers and toes. Individuals with low vitamin B-12 levels often lack classic symptoms until their levels are low for a significant period of time. I have met many adults in my family medicine practice who have no symptoms of their low vitamin B-12 levels., despite elevated methylmalonic acid levels. An elevated methylmalonic acid level verifies that the low vitamin B-12 level is significant.

For mothers who may have a restrictive diet, sharing good dietary sources of vitamin B-12 is important. These include animal products, such as dairy, meat, eggs, poultry, and fish. Nutritional yeast has vitamin B12, and many cows’ milk substitutes are fortified with vitamin B12, such as soy, coconut and almond milk.

Mothers who are taking metformin would likely benefit from taking a vitamin B-12 supplement. I monitor all of my patients who take metformin by checking a vitamin B-12 level at least every 12 months, and a large percentage require vitamin B-12 supplementation to keep their levels in a normal range.