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Universal improvement of B12 status appears “to be a nutritional imperative with possibly profound beneficial effects,” particularly at the bookends of life—at old age and infancy. I’ve explained the rationale for my recommendations to take vitamin B12 supplements once a week or once a day, or alternately eat sufficient daily B12-fortified foods. But for those over age 65, those guidelines go out the window. The recommendations change to everyone taking a high daily dose of 1,000 mcg every day.

Starting at age 50, everyone––meat-eaters and vegans alike––should be taking B12 supplements or eating B12-fortified foods. But over age 65, 50 a day may not do it. Even 100 a day doesn’t seem sufficient. Researchers investigated three doses, and found that most didn’t normalize their MMA until after the 1,000 microgram dose. (MMA suppression is a measure of B12 sufficiency.) But they just tested 25, 100, and 1,000. Maybe 250 or 500 would do it?

Researchers set out to find an adequate dose at that age, and it seems we need at least about 650 to 1,000 a day in most people, hence my 1,000-a-day recommendation after age 65.

Okay, what about the other end of the life cycle? The consequences of B12 deficiency and insufficiency can be devastating in infancy and childhood. And this is not just a problem for plant-based pregnancies. “Vitamin B-12 insufficiency during pregnancy is common even in nonvegetarian populations.” About a quarter of all pregnant women aren’t getting enough B12, and that number rises to nearly one in three by the third trimester. But, insufficiency isn’t as bad as frank deficiency, which can manifest in cases like cerebral atrophy, meaning brain shrinkage, in a “Vitamin B12-deficient Infant of a Vegetarian Mother.” Thankfully, even severe brain atrophy can be substantially reversed with B12 supplementation, but better not to become deficient in the first place.

The solution proposed by a group of French pediatricians is to recommend against raising vegan kids at all, since B12 supplementation is necessary. And they’re not alone. To vegan or not to vegan. In 2016, two professional organizations, the U.S. Academy of Nutrition and Dietetics and the German Nutrition Society, issued conflicting statements. The U.S. Academy said that even strictly plant-based diets are appropriate for all stages of the life cycle, whereas the German group echoed the French group, saying since you have to take B12, we can’t recommend a vegan diet for pregnant women, lactating women, infants, children, or adolescents. To confuse the matter further, the American Academy of Pediatrics appeared to have it both ways; in one place repeating the U.S. Academy’s position, while in another place it stated that vegan diets should not be recommended for children. But I think they’re just saying the same thing. Everyone agrees that a non-B12 supplemented plant-based diet is a bad idea—that’s part of what the U.S. Academy means by “well-planned.” Everyone eating plant-based, but especially pregnant and breastfeeding women, must ensure a regular, reliable source of vitamin B12, meaning B12 supplements or B12-fortified foods. But then you may be able to get the best of both worlds.

That’s why there are reviews with titles like this: plant-based pregnancies: danger or panacea? Danger if you don’t take your B12 but “following a plant-[based] diet during pregnancy may be protective against the development of preeclampsia, pre-gravid obesity, and minimize the exposure to [DNA-damaging] agents.” It may also protect our newborns “from the onset of pediatric diseases, such as pediatric wheezing, diabetes, neural tube defects, orofacial clefts, and some pediatric tumors.” “Vegan pregnant women have a lower-than-average rate of cesarean section, less postpartum depression, and lower neonatal and maternal mortality, with no complications or negative outcomes that are higher than average.” In addition, a lower incidence of what used to be called toxemia, a potentially dangerous pregnancy complication known as preeclampsia. “Overall, plant-based diets seem to confer protection to both mothers and newborns” by not only “reducing the risk of several pregnancy-related issues” but decreasing the risk of childhood disease. “Children following plant-based diets might have a lower risk of developing obesity,” obviously are less exposed to drugs used in animal production, and have a favorable anti-inflammatory profile of cell-signaling factors. But again, everyone on a plant-based diet has to get enough B12.

Pregnant and breastfeeding women can just follow my 50 micrograms a day recommendation for nonpregnant adults, or 2,000 a week, though they suggest breaking up those doses into two halves to boost absorption. After infants are weaned, they can start on 5 micrograms a day; from ages 4 through 10 they can take half the adult dose of 25 a day; and then at age 11, they can take 50 a day or 2,000 a week. You don’t have to worry about taking too much. It’s water-soluble and you’ll just end up with expensive pee.

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