Friday Favorites: The Optimal Vitamin B12 Dosage and Type

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Some of the most common questions I get are about the dosage and type of vitamin B12. Check out the video for some answers.

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.

Compared to non-vegetarians, those removing meat from their diets tend to have healthier body weights, cholesterol, blood sugars, and blood pressures, with a lower mortality rate due to ischemic heart disease, the #1 killer of men and women. However, underestimating the importance of correct supplementation of vitamin B12 can nullify these benefits. Currently, the official position of associations and governmental agencies is categorical and unequivocal: in the case of a vegetarian diet, even if you eat eggs and dairy—and, in fact, I would extend that to flexitarians eating a few servings of meat a week—supplementation of vitamin B12 is required.

Now, it’s not just those eating plant-based that should be concerned about getting enough B12. About one in three nonvegetarians aren’t getting enough for optimal health, and that may exceed half in women, especially when they’re pregnant. But this number could run as high as nearly 9 out of 10 among those eating strictly plant-based, and 10 out of 10 doing it long-term.

There are three groups of people who should ensure they have a regular, reliable source of vitamin B12 by supplementing their diet with vitamin B12-fortified foods or B12 supplements: those who’ve had bariatric surgery (which can sometimes impair absorption), those eating plant-based diets, and the more than a hundred million Americans older than age 50.

Why can’t you get regularly tested for signs of functional B12 deficiency, like getting your homocysteine or methylmalonic acid (MMA) level tested? Though those are nearly always elevated in cases of B12 deficiency, there are rare cases of severe B12 deficiency manifesting with normal B12 levels in the blood, normal MMA levels, and normal homocysteine. How do we know it was B12 deficiency? Because within months of B12 treatment, they made a remarkable recovery. So, best to just take it and not wait for symptoms to arise. The question is: how much, and how often?

Some recommend a single dose of 50 to 100 micrograms a day or a thousand micrograms twice a week. Others suggest 50 to 150 micrograms a day. Some even recommend 500 micrograms a day. It all depends on the target levels you want in your body. For those with normal absorption capacity, meaning being under age 50 with an intact gastrointestinal system and without diseases like pernicious anemia, we normally lose about one microgram of vitamin B12 a day; so, that’s how much we have to replace, on average, every day. So, why is the Recommended Daily Allowance 2.4 micrograms a day? Well, we only absorb about half of the tiny doses of the B12 we get in our diet; so, by eating 2.4, we can make sure we absorb the one microgram into our body to replace the one microgram we’re losing every day.

Taking larger doses, like in supplement form, an even smaller fraction is absorbed. So, it might take a single oral dose of 10 micrograms to get that one microgram absorption. But just 10 a day failed to sufficiently lower homocysteine levels to under 10 even after a year; so, maybe we need to absorb more than that 1.6 micrograms every day for optimal health. The current RDA is primarily based on a 1958 study that just looked at a small number of patients, and only measured their blood counts. Absorbing one microgram a day may be enough to maintain blood cell production, but may not be sufficient for all the other things that vitamin B12 does.

“Based on the data of several vitamin B12 status biomarkers studies,” maybe the recommended intake for most adults should be raised to more like four, which is what you see for example in Europe, suggesting they want people to absorb at least two into their body every day. In that case you’d need to take more than 50 a day. And, now we have data suggesting getting seven a day may be even better. So, if you wanted to absorb 3.5 micrograms, half of the intake that may optimize functional B12 status, how much would you need to take in a single daily dose? This chart isn’t granular enough, but there’s a formula you can use to calculate it. U stands for uptake––absorption into your body––and D is your single daily dose. To absorb 3.5, you’d theoretically need to take a single daily dose of about 225, which I round in my recommendations to 250 a day.

Now, that’s just one of three methods you can use. A simpler and cheaper way is to take a single dose a week. If you want 3.5 in you a day, then you’d want to get at least 24.5 in you in a week. To get that in a single dose you’d have to theoretically take about 2,600, which I round in my recommendations to 2,500. Okay, but that’s theoretical. Maybe you need even more? On the contrary, a new study showed you can get away with even less. Just 50 a day (not 250, or 2,000 once a week, not 2,500) reliably bought blood levels up, and more importantly, normalized methylmalonic acid and homocysteine levels within a matter of months. So, based on this new study, I dropped my supplement recommendations down to that 50 a day or 2000 a week.

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• Rizzo G, Laganà AS, Rapisarda AM, et al. Vitamin B12 among Vegetarians: Status, Assessment and Supplementation. Nutrients. 2016;8(12)
• Smith AD, Warren MJ, Refsum H. Vitamin B. Adv Food Nutr Res. 2018;83:215-279.
• Waldmann A, Koschizke JW, Leitzmann C, Hahn A. German vegan study: diet, life-style factors, and cardiovascular risk profile. Ann Nutr Metab. 2005;49(6):366-72.
• Langan RC, Goodbred AJ. Vitamin B12 Deficiency: Recognition and Management. Am Fam Physician. 2017;96(6):384-389.
• Graber JJ, Sherman FT, Kaufmann H, Kolodny EH, Sathe S. Vitamin B12-responsive severe leukoencephalopathy and autonomic dysfunction in a patient with "normal" serum B12 levels. J Neurol Neurosurg Psychiatry. 2010;81(12):1369-71.
• Obeid R, Herrmann W. Vitamin B12 supplementation, how much, how often, how long? In: Herrmann W, Obeid R, eds. Vitamins in the Prevention of Human Diseases. Walter de Gruyter; 2011. 7-39.
• Sukumar N, Saravanan P. Investigating vitamin B12 deficiency. BMJ. 2019;365:l1865.
• Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood. 2008;112(6):2214-21.
• Deshmukh US, Joglekar CV, Lubree HG, et al. Effect of physiological doses of oral vitamin B12 on plasma homocysteine: a randomized, placebo-controlled, double-blind trial in India. Eur J Clin Nutr. 2010;64(5):495-502.
• Bor MV, Von castel-roberts KM, Kauwell GP, et al. Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population. Am J Clin Nutr. 2010;91(3):571-7.
• Darby WJ, Bridgforth EB, Le brocquy J, et al. Vitamin B12 requirement of adult man. Am J Med. 1958;25(5):726-32.
• Ströhle A, Richter M, González-gross M, et al. The Revised D-A-CH-Reference Values for the Intake of Vitamin B : Prevention of Deficiency and Beyond. Mol Nutr Food Res. 2019;63(6):e1801178.
• EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2015. Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12). EFSA Journal 2015; 13( 7):4150, 64 pp.
• Pentieva, K., Hughes, C., Askin, N., Hoey, L., Molloy, A., Scott, J., & McNulty, H. (2012). An intervention trial to determine the response of vitamin B12 biomarkers to chronic supplementation with low dose vitamin B12 after folate repletion. Proceedings of the Nutrition Society, 71(OCE2), E138.
• Berlin H, Berlin R, Brante G. Oral treatment of pernicious anemia with high doses of vitamin B12 without intrinsic factor. Acta Med Scand. 1968;184(4):247-58.
• Del bo' C, Riso P, Gardana C, Brusamolino A, Battezzati A, Ciappellano S. Effect of two different sublingual dosages of vitamin B on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial. Clin Nutr. 2019;38(2):575-583.
• Green R, Allen LH, Bjørke-monsen AL, et al. Vitamin B deficiency. Nat Rev Dis Primers. 2017;3:17040.
• Macfarlane AJ, Shi Y, Greene-finestone LS. High-dose compared with low-dose vitamin B-12 supplement use is not associated with higher vitamin B-12 status in children, adolescents, and older adults. J Nutr. 2014;144(6):915-20.
• Rajan S, Wallace JI, Brodkin KI, Beresford SA, Allen RH, Stabler SP. Response of elevated methylmalonic acid to three dose levels of oral cobalamin in older adults. J Am Geriatr Soc. 2002;50(11):1789-95.
• Eussen SJ, De groot LC, Clarke R, et al. Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency: a dose-finding trial. Arch Intern Med. 2005;165(10):1167-72.
• Smith AD, Warren MJ, Refsum H. Vitamin B. Adv Food Nutr Res. 2018;83:215-279.
• Sukumar N, Rafnsson SB, Kandala NB, Bhopal R, Yajnik CS, Saravanan P. Prevalence of vitamin B-12 insufficiency during pregnancy and its effect on offspring birth weight: a systematic review and meta-analysis. Am J Clin Nutr. 2016;103(5):1232-51.
• Kocaoglu C, Akin F, Caksen H, Böke SB, Arslan S, Aygün S. Cerebral atrophy in a vitamin B12-deficient infant of a vegetarian mother. J Health Popul Nutr. 2014;32(2):367-71.
• Lövblad K, Ramelli G, Remonda L, Nirkko AC, Ozdoba C, Schroth G. Retardation of myelination due to dietary vitamin B12 deficiency: cranial MRI findings. Pediatr Radiol. 1997;27(2):155-8.
• Lemale J, Mas E, Jung C, Bellaiche M, Tounian P. Vegan diet in children and adolescents. Recommendations from the French-speaking Pediatric Hepatology, Gastroenterology and Nutrition Group (GFHGNP). Arch Pediatr. 2019;26(7):442-450.
• Pawlak R. To vegan or not to vegan when pregnant, lactating or feeding young children. Eur J Clin Nutr. 2017;71(11):1259-1262.
• Piccoli GB, Clari R, Vigotti FN, et al. Vegan-vegetarian diets in pregnancy: danger or panacea? A systematic narrative review. BJOG. 2015;122(5):623-33.
• Baroni L, Goggi S, Battaglino R, et al. Vegan Nutrition for Mothers and Children: Practical Tools for Healthcare Providers. Nutrients. 2018;11(1)
• Pistollato F, Sumalla cano S, Elio I, Masias vergara M, Giampieri F, Battino M. Plant-Based and Plant-Rich Diet Patterns during Gestation: Beneficial Effects and Possible Shortcomings. Adv Nutr. 2015;6(5):581-91.

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