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Vitamin D on a plant based diet: what the doctors say
Vitamin D on a plant based diet: what McDougall, Esselstyn, Barnard, Goldhamer and other doctors say about sun, pills and testing, with sources.
Updated . For education only, not medical advice.
Our view
Vitamin D is less a food nutrient than a hormone the skin produces when sunlight reaches it, a point McDougall, Campbell and Goldhamer all make123. That sets it apart from B12: McDougall, who tells people on his diet to take B12, does not tell them to take D4.
We give most weight to the low-fat clinicians who have treated patients for decades, and on this nutrient their line is sun first, with a blood test and a supplement only when the level is low or sun is scarce5678. Neal Barnard leans further toward a routine pill, mainly because sunscreen and indoor life block what the sun would give9.
The case for pills in people who are not deficient is weaker than the case for B12: McDougall, Nelson and Novick each pointed to trials that found little or no benefit, or even harm with high doses101112. So unlike B12, vitamin D is a question of your own sun, skin and blood level rather than one rule for everyone58.
Where they agree
Sunlight is the natural source, and almost every doctor here names it before any pill: McDougall, Campbell, Rogers, Goldhamer and the Ornish program all prefer the sun5213314. Even Barnard, who favors a supplement, starts from the time in the sun that can supply it9.
They also agree that some people do not get enough from the sun and then need another source: Lisle told strict vegans to make sure of sunshine or something else, and Goldhamer kept a supplement for people whose sun exposure leaves the level short157. Novick listed who is most at risk, among them breastfed infants, the elderly, anyone dark skinned or rarely in the sun and people with obesity or gut problems that block fat absorption8.
Skin color matters to all who discuss it: McDougall said darker skin needs three to ten times as much sun, and Novick counted dark skin as a risk factor58. Lisle traces lighter skin in northern peoples to this very need, an adaptation to make enough of the vitamin and avoid rickets16.
Where they differ
The doctors split on whether a pill is needed at all, how much, how much sun is enough, whether to test, and what the trials show417811.
Whether a pill is needed
McDougall said in 2015 that he advises B12 but not vitamin D, and Nelson said in 2018 that he takes none and sees it as needless for most people411. Barnard, in 2021, said a supplement makes sense for people who wear sunscreen or stay indoors9, and Ornish said in 2019 that he takes about 1,000 units a day18. Campbell has moved back and forth: in 2013 he said he could accept a supplement to be safe when stores drop, in 2021 he saw no need for one himself, and in 2024 he said his own blood level was rated low despite time outdoors192021.
Dose
The amounts named range from about 1,000 units a day for Ornish to 2,000 for Barnard and 2,000 to 4,000 of D3 for the patients Goldhamer supplements181722. Barnard also warned against the high end, saying in 2021 that 5,000 units or more risks an overdose and in 2023 that 5,000 to 10,000 could be toxic1723. On the form, Goldhamer noted that D is usually made from lanolin in sheep’s wool and that a vegan version now exists24.
How much sun
McDougall gave the smallest figure: for a light-skinned person near Boston from spring to fall, a few weekly sessions of five minutes in the midday sun, with face, arms and hands bare5. Barnard spoke of 20 to 30 minutes on the face and arms9, and Rogers said in 2024 that he simply sits outside for half an hour with a book25. The Ornish program’s site puts the yield of 10 to 15 minutes of summer sun at roughly 3,000 to 5,000 IU26.
Testing
Barnard argued in 2021 for routine testing, since a shortfall cannot be felt27, and Esselstyn’s FAQ asks for a blood test with a supplement only to keep the level low normal6. Goldhamer tests supplemented patients every year because the vitamin is fat soluble, so unlike B12 an excess is a concern22. Novick limited testing to people at risk, with a second test about three months after raising a low level8. Campbell and Rogers doubt what the usual test shows: both say the active form made in the kidney and other tissues matters more than the stored form the lab measures2825.
What the trials show
In 2015 McDougall cited a pooled analysis of 46 randomized trials, close to 250,000 people in all, that found no benefit from supplements, plus two big high-dose studies in older adults living independently, where falls and fractures went up1029. In 2019 he told Ornish that recent trials, VITAL among them, had been largely negative for vitamin D pills30. Nelson noted in 2018 that a US task force had just advised against vitamin D to prevent falls in older adults living at home31, while Novick wrote in 2011 that the fracture benefit was found mainly in older adults in institutions taking it with calcium32. Barnard was more hopeful in 2023, linking vitamin D to calcium absorption, possibly lower cancer risk and, in newer data, less Alzheimer’s disease33.
Low levels: cause or sign
McDougall argued in 2015 that illnesses seen more often at high latitudes follow the rich food of those regions rather than the lack of sun, and that a low blood level often reflects inflammation or obesity3435. Campbell suggested in 2013 that an acid state, which diets rich in animal protein can cause, may slow the conversion to the active form36, and Rogers said in 2021 that the heavy calcium load of dairy makes that conversion less likely37.
What each expert says
JMJohn McDougall
McDougall does not advise vitamin D pills: in 2015 he said plants make all but two of the 13 vitamins, and that he recommends B12 from that pair but not D4. He held that brief noon sun a few times a week is enough even at the latitude of Boston, with more for darker skin5. In 2024 he described the vitamin as a hormone made by the skin in sunlight1.
Esselstyn’s FAQ, read in 2026, names no routine dose6. It asks for a blood test and a supplement only as needed to hold the level in the low normal range6.
In 2013 Campbell said the active form of vitamin D matters more than the stored form most studies measure, and that he could accept supplements when stores fall2819. In 2021 he linked vitamin D to sunshine and saw no need to supplement himself20. In 2024 he called the sun the best source while noting that his own level, near 20, was rated low221.
Barnard said in 2021 that sunscreen and indoor life block the sun’s vitamin D, so a supplement of about 2,000 IU a day makes sense, with 5,000 or more risking excess917. He wants testing to be routine27. In 2023 he repeated the dose and linked the vitamin to calcium absorption and possibly lower risk of cancer and Alzheimer’s disease2333.
In a 2019 webinar with McDougall, Ornish said he takes a small amount of vitamin D, about 1,000 units daily18. His program’s site favors sunlight over food, comparing ten minutes of summer sun to some thirty glasses of milk14.
In 2017 Goldhamer described vitamin D as a natural hormone that sunlight lets us form, adding that a simple blood test shows if a person should get more sun or take a supplement3. His patients who take it are tested each year, and most of them need a daily D3 dose in the range of 2,000 to 4,000 units22. In 2022 he again listed it only for people who lack sun7.
Rogers said in 2022 that vitamin D from the sun beats a pill, noting that McDougall kept pills for people unable to get outdoors13. In 2024 he described his half hour of sun with a book and stressed the activated form over the one blood tests report25.
In 2012 Novick did not back routine pills but advised people at risk to test, work with their clinician to lift a low level through sun, UV lamps, pills or a mix, then retest three months later8. In 2011 he wrote that enough vitamin D lowers the risk of broken bones, chiefly for older people who rarely go out, while the evidence for cancer or heart protection was thin12.
In a 2018 video Nelson said he takes no vitamin D and considers it unnecessary except for a small group with specific problems11. He pointed to the 2018 US task force advice against it for preventing falls and to a 56-trial review whose authors warned against using it to promote supplements for longer life3138.
Rip Esselstyn’s PLANTSTRONG site lists vitamin D among the nutrients beginners should watch39. A 2025 podcast post featured the head of the supplement company Complement, who named D3 an essential, while Esselstyn’s own line was that supplements come after a whole food diet40. The post also offered readers a 30% code off Complement products41.
In a 2017 webinar Lisle told strict vegans to secure enough sunshine or another vitamin D source15. In 2021 he said pale skin evolved in the north to let in more sunlight, so people there could make the vitamin and avoid rickets16.
We treat regular sun as the first source of vitamin D, as most of these doctors do572. Whether you need a blood test or a supplement depends on your skin, your latitude, your age and how much time you spend outdoors, so that is a question 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.