Vitamin B12 on a plant based diet: what the doctors say
Vitamin B12 on a plant based diet: what McDougall, Esselstyn, Campbell, Barnard and other doctors say, where they agree and differ, with sources.
Updated . For education only, not medical advice.
Our view
Vitamin B12 is not made by plants or by animals but by bacteria; meat, eggs and milk carry it only because animals store what microbes produced12. People once swallowed some of those microbes with soil and unwashed food, and modern hygiene has largely taken that source away34.
So B12 is the one nutrient on which a fully plant based diet needs a plan, and almost every doctor on this site says so, from John McDougall and Caldwell Esselstyn to Neal Barnard and Alan Goldhamer5637. The body keeps a large reserve, so a shortfall builds over years, not weeks, which is why it is easy to ignore until it does harm18.
We give most weight to the clinicians who have fed thousands of patients this way for decades, and they agree on the core point: take a reliable source of B12910. Even the doctors who doubt the case for supplements, T. Colin Campbell and, for a while in 2026, Peter Rogers, ended up taking B12 themselves1112.
Where they agree
Bacteria make B12, not plants or animals; McDougall, Barnard and Campbell all start from that point1213. They also agree the body hoards the vitamin: McDougall put the time to run out at 20 to 30 years without good sources, while Ornish and Rogers speak of a reserve lasting several years1814.
On what to do, the agreement is broad: McDougall, Esselstyn, Barnard, Ornish, Goldhamer, Novick and Rip Esselstyn all tell people who eat no animal foods to have a dependable B12 source, usually a supplement51538161718. Walter Willett and Doug Lisle put it more briefly: someone fully vegan has to watch B121920.
They also agree that a real shortfall is serious when left alone; Goldhamer has treated anemia and nerve damage from it, mostly in people on extreme vegan or fruit-only diets, and saw them recover with supplements10. McDougall described the early signs as mild and reversible, with lasting nerve damage possible if the lack goes on5. Barnard adds that low B12 is not only a vegan issue: it also shows up in meat eaters past 50 and in people taking metformin or acid blockers21.
Where they differ
The doctors part ways on the details: how much to take, in what form, from pills or fortified foods, whether to test, and for a few, whether supplements are needed at all222311.
Dose
The amounts they name span a thousandfold: McDougall chose 5 micrograms a day as a safety margin above the fraction of a microgram that has cured the anemia24, and still gave that figure in 2022 while noting that shop pills hold 500 to 5,000 micrograms25. Goldhamer’s center gives 1,000 micrograms of methylcobalamin daily16, and Jeff Nelson went back to 500 micrograms two or three times a week26. The Ornish program explains part of the gap: from a 500 microgram pill a healthy person absorbs only about 1027.
Form and route
Rogers prefers methylcobalamin, the form he calls active, dissolved under the tongue to bypass the gut’s slow absorption route2829. McDougall, having read two papers that disagreed on the best form, suggested mixing methyl, hydroxy and cyano forms or taking them in turn22. On injections, Goldhamer favors pills, which he sees as low risk because the body passes the excess in urine30, and Barnard says supplements are well absorbed even in people short of stomach acid21.
Pills or fortified foods
The Ornish site points to fortified cereals and nutritional yeast31, and Rip Esselstyn’s PLANTSTRONG brand sells plant milks fortified with B1232. Jeff Novick does not trust nutritional yeast for B12, since not every brand adds it and the vitamin degrades in light, for example in bulk bins33. Barnard’s group calls a daily supplement simpler and more reliable than fortified foods34.
Testing
Nelson advises a blood test now and then, because levels can end up too high as well as too low23. Rogers suggested aiming for roughly 500 to 1,500 on the blood test35.
Whether everyone needs it
Campbell is the main skeptic: in 2017 he said he follows his clinician friends on B12 while doubting the science is settled, and in 2024 he said he takes it at his wife’s request without being sure everyone needs it3611. Rogers stopped B12 in March 2026 after reading a book that calls it a myth, resumed within weeks at a lower dose, and by May said he could not advise anyone to go without it373812.
Older views
Some positions belong to their dates: in a 1996 article Campbell argued that plants, especially organic ones, carry B12 from soil microbes, then wrote in a later note dated 2008 that Michael Greger and Alan Goldhamer had convinced him vegans can run short3940. In 1982 Nathan Pritikin said he had added back small amounts of animal food because he saw no other way to get B1241. In 2019 Ornish described B12 as coming only from animal foods, a view the other doctors here correct by pointing to bacteria82.
What each expert says
JMJohn McDougall
McDougall saw B12 as the one fair criticism of his starch-based diet, while rating the risk of disease from it on a sensible vegan diet as tiny42. For decades the front of his books asked anyone pregnant, nursing or past three years on his diet to take at least 5 micrograms daily9. In 2022 he admitted he takes his own only every few months, when he remembers22.
Esselstyn’s heart program, in its 2014 report on 198 patients, encouraged a B12 supplement along with a multivitamin6. His site’s FAQ, read in 2026, still asks for B12 while calling a multivitamin unneeded for people who eat plenty of leafy greens15. In a 2009 talk he listed B12 with folate and B6 as the vitamins that keep homocysteine, a heart risk marker, under control43.
Campbell’s view moved over time, from B12 in organic plants (1996) to deferring to clinicians on supplements (2008)3940. He accepts that blood B12 falls on an all plant diet across many studies44, and in 2021 named it the only single-nutrient supplement with some evidence behind it45. He still questions whether everyone needs it11.
Barnard calls a B12 pill insurance and encourages every vegan to take one3. He points out that the US advice to supplement after 50 applies to meat eaters too, because many lack the stomach acid to free B12 from food21.
In 2019 Ornish said B12 matters mainly for strict vegans, that body stores last five to seven years, and that vegans should still supplement8. His program’s site warns that a low-fat vegan diet may contain none and lists fortified foods as sources31.
At Goldhamer’s TrueNorth Health Center the daily B12 is a 1,000 microgram dose of methylcobalamin16. In his view the B12 in food comes from bacteria on it, which we now wash and peel away, so vegans need a supplement7. Over some 40 years he has seen more deficiency than most doctors10.
In 2021 Rogers expected every full vegan, himself included, to run low eventually and recommended sublingual methylcobalamin1429. After his 2026 pause and restart he settled on a tiny intake, roughly a tablet each two months, and called the question open46. In July 2026 B12 was the only supplement he said he takes47.
Novick wrote in 2012 that anyone who eats no animal foods has created a need for a reliable B12 source, likely a supplement17. He also skips nutritional yeast for its calorie density, about 1,700 calories per pound48.
Nelson paused B12 in 2019 after a test showed his level far above the range, and a February 2020 video on high levels was widely read as advice to stop4950. A month later he said he does recommend B12 for vegans and was taking it again5126.
Rip Esselstyn’s PLANTSTRONG site lists B12 among the nutrients beginners should watch and suggests a supplement18. His company also sells plant milks fortified with B12, vitamin D3 and calcium, still sold that way after a 2026 update3252.
When Chef AJ logged a day of her meals in a tracker in 2019, B12 was the only nutrient she came up short on, and she said she covers it with a supplement53. In 2024 she said she still takes B12 and vitamin D54.
Lisle sees B12, with vitamin D, as the deficiency a strict vegan should watch, and lists it among the possible causes when someone on a plant based diet feels tired2055.
On a fully plant based diet, we treat a reliable B12 source as part of the plan, as nearly all of these doctors do573. Which dose, which form and whether to test are the points where they differ, so those are questions for your own doctor. This page is education, not medical advice.
Each small number links to its reference below: the video at the exact second, or the page where it was said.