What each one does, what the research found, and the form that goes in the scoop.
Vitamin B12
Daily Value 2.4 mcg
B12 is made by bacteria, not plants. Unfortified plant foods contain essentially none of it. This is the least controversial claim in all of plant-based nutrition.
0.24–0.49 mcg
Average daily B12 intake among vegans across 48 studies in a WHO-supported systematic review — against a 2.4 mcg recommendation. That’s a fifth of the target at best.
Bakaloudi et al., Clinical Nutrition, 2021 — read the review →
Every life stage
A review of 40 studies across the full lifecycle found deficiency consistently higher in vegans than in other vegetarians, including in pregnancy and in infants of vegan mothers. The authors concluded unsupplemented vegans are at especially high risk.
Pawlak, Lester & Babatunde, European Journal of Clinical Nutrition, 2014 — read the review →
Fortify or supplement
A 2024 scoping review examined the intervention evidence on closing the B12 gap and found the practical routes are fortified foods and supplements — the nutrient has to come from outside an unfortified plant diet. Fortification is the mechanism, not an afterthought.
Fernandes et al., Nutrients, 2024 — read the review →
What’s in the scoop
Cyanocobalamin. It’s the most stable form in a dry powder matrix, and the form the majority of the B12 research was run on — so what we put in is what was measured.
Iodine
Daily Value 150 mcg
Iodine comes from seawater, seafood, dairy, and iodized salt. Crops grown on inland soil carry very little. Seaweed varies so wildly by species and harvest that it can’t be relied on. This is the best-documented gap of the eight.
5 out of 5
Every study in the meta-analysis that measured urinary iodine found vegans significantly lower than omnivores. Median vegan values ran from 12.2 to 44.0 mcg/L; the WHO adequate range is 100–200. Every vegan group landed in moderate-to-severe deficiency territory, and no dietary group in the review — vegan, vegetarian or omnivore — reached the adequate range at all.
Eveleigh, Coneyworth & Welham, British Journal of Nutrition, 2023 — eleven studies covering 4,421 adults; urinary iodine measured in five of them, across 700 participants. read the meta-analysis →
80%
Share of vegans below the iodine deficiency threshold in a direct urinary excretion study, against 9% of omnivores. A small study — 15 vegans, 31 vegetarians, 35 omnivores — but it measured excretion directly rather than estimating intake.
Krajcovicova-Kudlackova et al., Annals of Nutrition and Metabolism, 2003 — read the study →
What’s in the scoop
Potassium iodide, at a dose set to close the gap without stacking on top of iodized salt. More is not better with iodine — excess causes the same thyroid problems as deficiency.
Selenium
Daily Value 55 mcg
Selenium in plants is entirely a function of the soil they grew in. In selenium-rich regions, plant foods deliver plenty. Across much of Europe and the UK, soils are depleted and plant intake becomes unreliable. Animal foods buffer this because selenium accumulates up the food chain.
24.7 mcg/day
Average selenium intake in vegan women in a UK study — under half the 55 mcg US Daily Value, and below the UK’s own 40 mcg Lower Reference Nutrient Intake, the floor below which intake is considered inadequate for nearly everyone. Vegetarians didn’t clear that floor either. (Two reference frameworks, named so you can check both.)
Eveleigh et al., Frontiers in Nutrition, 2020 — read the study →
12 months, no change
In a controlled 12-month study of 172 people, vegans showed lower Selenoprotein P — a functional marker more sensitive than raw serum selenium — even when total serum selenium looked normal. Optimised plant-based meal plans did not meaningfully improve it over the year.
Klein et al. (NuEva Study), Nutrients, 2023 — read the study →
What’s in the scoop
Sodium selenite. Selenium has one of the narrowest safe ranges of any mineral, so the dose is set conservatively against the 55 mcg DV, not stacked toward the upper limit.
Zinc
Daily Value 11 mg
Zinc is in legumes, grains, nuts and seeds. So is phytic acid, which binds zinc and blocks its absorption. The foods that supply it are the same foods that hold it back — which is why eating more of them only partly helps.
+50%
How much more zinc the Institute of Medicine recommends vegetarians consume compared with omnivores, specifically to offset the lower bioavailability. That’s the official acknowledgement that the gap is real.
Foster & Samman, Advances in Food and Nutrition Research, 2015 — read the review →
Both markers, lower
The NuEva study found zinc intake significantly lower and Phytate Diet Score significantly higher in vegans, with reduced total serum zinc and reduced free zinc — the more sensitive of the two. Women were most affected.
Klein et al. (NuEva Study), Nutrients, 2023 — read the study →
What’s in the scoop
Zinc bisglycinate. Zinc bound to glycine is absorbed through a different route than free zinc ions, so phytate in the rest of your meal has far less opportunity to bind it. Adding cheap zinc oxide to a phytate-heavy diet mostly feeds the phytate.
Vitamin D3
Daily Value 20 mcg
Plant foods contain no meaningful D3. It’s in fatty fish, egg yolks and liver — or it’s made in your skin from sunlight. Which works, until it’s winter, or you work indoors, or you have darker skin, or you wear sunscreen.
3–67% vs 0–6%
Across a systematic review of 141 studies, vitamin D deficiency ran from 3% to 67% in vegans, against 0% to 6% in meat-eaters. The review also found vitamin D intake and status generally lower across plant-based patterns. Disclosure: both authors work at Unilever. It’s peer-reviewed, not a white paper, and we’d rather tell you than have you find it.
Neufingerl & Eilander, Nutrients, 2022 — read the review →
93.7%
Share of a 300-adult Spanish study — omnivores, lacto-ovo vegetarians and vegans together — below the vitamin D sufficiency threshold. Frank deficiency was significantly more common in the vegans than in the other two groups. Note the first number: this is close to universal, and the vegan disadvantage sits on top of a population-wide problem.
Gallego-Narbón et al., Nutrients, 2024 — read the study →
Named by the NIH
The NIH Office of Dietary Supplements states outright that vitamin D deficiency is more common in people following vegan or ovo-vegetarian diets, because the highest-density food sources are all animal-derived. It notes the only natural plant sources are certain mushrooms, in small and variable amounts.
NIH Office of Dietary Supplements, Vitamin D Fact Sheet — read the fact sheet →
The honest caveat
Blood vitamin D is driven more by sunlight than by diet, and some cohort studies find little difference between vegetarians and omnivores for exactly that reason. So we’re not claiming diet is the main lever. Our position is narrower: the dietary contribution on a vegan diet is essentially zero, which leaves you wholly dependent on sun exposure that most people in temperate climates can’t reliably get for four to six months a year.
What’s in the scoop
Cholecalciferol (D3), not ergocalciferol (D2). D3 raises and holds blood levels better than D2. Most commercial D3 is extracted from lanolin, which comes from sheep’s wool and is not vegan. Ours is lichen-derived, so the whole bag stays plant-based.
Iron
Daily Value 18 mg
Lentils, spinach and tofu are loaded with iron. Vegans eat plenty of it. Anyone telling you plants don’t have iron is wrong — and that’s not our argument. Our argument is about what happens after you swallow it.
The finding most iron labels won’t show you
The WHO-supported systematic review of 48 studies concluded that vegan diets are not related to deficiencies in iron. On intake, vegans are fine. We’re publishing that because it’s true, and because the next number is the one that matters. Read it yourself →
−29.7 mcg/L
And yet: pooling 24 studies, adult vegetarians carry significantly lower serum ferritin — the marker for iron stores — than omnivores. The gap is real and statistically solid (95% CI −39.7 to −19.7, p<0.01). Intake is fine. Stores are not. The difference is that plant iron is non-heme iron, absorbed at a fraction of the rate of heme iron, and actively blocked by the phytates and polyphenols in the same meal.
Haider et al., Critical Reviews in Food Science and Nutrition, 2018 — read the meta-analysis →
12–79%
Range of ferritin deficiency among female vegetarians across 13 studies in 10 countries — consistently above non-vegetarian controls. Premenopausal women carry the most risk.
Craig, American Journal of Lifestyle Medicine, 2018 — read the review →
What’s in the scoop
Iron bisglycinate, and absorption is exactly why. Chelated to glycine, it bypasses much of the phytate interference that limits ordinary non-heme iron, and it’s markedly gentler on the gut than ferrous sulfate. Since the problem is absorption rather than intake, the right answer is a better-absorbed form at a sensible dose, not a megadose of a cheap one.
Choline
Adequate Intake 550 mg / 425 mg
Choline is concentrated in eggs, liver, fish and beef. Soybeans, broccoli and wheat germ have some. Hitting the adequate intake from plants alone is possible but takes real planning, and most people don’t do it — vegan or not.
205 vs 270 mg
Daily choline intake in pregnant vegetarians and vegans versus pregnant omnivores in a study of 283 women (p<0.0001). Worth noting: only 7% of all the women hit the adequate intake. The plant-based group was lower still, from an already low baseline.
Müller et al., Nutrients, 2022 — read the study →
All animal foods
A BMJ analysis identified every primary dietary source of choline as animal-derived — beef, eggs, dairy, fish, poultry — with plant foods supplying small amounts only. It argued the shift away from animal products carries an under-recognised choline cost, most acute in pregnancy.
Derbyshire, BMJ Nutrition, Prevention & Health, 2019 — read the analysis →
Where we draw the line
What’s documented here is an intake shortfall, not a clinical deficiency — and we’re labelling it that way rather than blurring the two. The case is strongest exactly where the requirement spikes: pregnancy and fetal brain development.
What’s in the scoop
Choline bitartrate. Choline is bulky — a full DV would dominate the scoop — so this is a meaningful contribution toward the target, not the whole thing. We’d rather say that than imply otherwise.
Vitamin A
Daily Value 900 mcg RAE
Plants contain zero retinol. What they contain is beta-carotene, which your body converts into retinol. Every reassuring vitamin A statistic you’ve read assumes that conversion works. Two separate things decide whether it does — how the vegetable was prepared, and which genes you inherited — and they stack.
What the intake data says
The WHO-supported systematic review states that vegan diets are not related to deficiencies in vitamin A. On population intake, that’s correct, and we’re not going to claim a deficiency epidemic that doesn’t exist. But that data counts beta-carotene at a flat exchange rate, applied to everyone equally. Read it yourself →
12 to 1
The Institute of Medicine’s conversion figure: 12 mcg of dietary beta-carotene yields 1 mcg of retinol activity. Hitting 900 mcg RAE that way means about 10.8 mg of beta-carotene daily, eaten with enough fat to absorb it. The IOM itself notes this varies with fat intake, cooking method, food matrix and individual physiology.
Institute of Medicine, Dietary Reference Intakes, 2001 — read the DRI report →
3% → 39%
How much beta-carotene was released from carrots in a lab digestion model: 3% from raw pieces, 21% pulped, 27% cooked, 39% cooked with oil. This is bioaccessibility in vitro, not absorption in a person — but it shows how much of the conversion question is settled by how the vegetable was prepared, before genetics enter the picture at all.
Hedrén et al., European Journal of Clinical Nutrition, 2002 — read the study →
About 45%
Estimated share of the population carrying common variants of the BCO1 gene — R267S and A379V — which encode the enzyme that performs the conversion. Carriers produce meaningfully less retinol from the same beta-carotene. Cooking your carrots in oil helps everyone; it doesn’t change which enzyme you inherited.
Borel & Desmarchelier, Nutrients, 2017 — read the paper →
What’s in the scoop
Vitamin A palmitate — preformed retinol, ready to use, no conversion step required. Our claim is precise: not that vegans are deficient in vitamin A, but that a large subset converts beta-carotene poorly, and preformed retinol removes that variable entirely.
