B12 is settled. The rest is a real spectrum, not a coin flip
This page reports what the evidence and the named dietetic and health bodies actually say, attributed to whoever says it. It isn't a recommendation of what you personally should take, and it isn't medical advice. For pregnancy, lactation, infancy, a diagnosed deficiency, or an existing health condition, the standing position from every body cited below is the same: get individual guidance from a registered dietitian or doctor rather than deciding from a supplement label.
| Nutrient | What's genuinely settled | Who says it |
|---|---|---|
| Vitamin B12 | A supplement or fortified food is necessary; no plant food is a reliable source | Academy of Nutrition and Dietetics, NIH Office of Dietary Supplements, British Dietetic Association |
| Omega-3 (EPA/DHA) | Algae oil is the reliable route to preformed EPA/DHA; not established as universally required | Academy of Nutrition and Dietetics, British Dietetic Association |
| Iodine | A genuine risk without iodized salt or fortified foods; both too little and too much cause harm | Academy of Nutrition and Dietetics, British Dietetic Association |
| Vitamin D | Shortfall is common in winter and at high latitudes for everyone, not specifically vegans | Academy of Nutrition and Dietetics |
| Iron and zinc | No adverse health consequences found from lower status in adult vegetarians; absorption adapts | Academy of Nutrition and Dietetics |
Vitamin B12: the one with no real debate
Three different bodies converge on the same point from three different angles. The Academy of Nutrition and Dietetics' position paper on vegetarian diets states plainly: Vegans need reliable sources of vitamin B-12, such as fortified foods or supplements. The NIH Office of Dietary Supplements explains why: vegans have a higher risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods. The British Dietetic Association puts it just as directly in its own fact sheet: The exception is vitamin B12. This nutrient is not available from plants. You will need to get this from fortified foods or a supplement. Fermented foods, spirulina, and nutritional yeast that isn't fortified do not reliably close this gap, whatever the label implies. For the full sourced picture, including the actual studies, see our evidence page on vitamin B12.
Where the other four actually stand
None of the remaining four deserves either the reassurance or the alarm this topic usually gets. Omega-3 is the clearest middle case: the Academy of Nutrition and Dietetics notes that evidence suggests the n-3 needs of healthy individuals can be met with ALA alone (found in flax, chia, walnuts, and their oils), with the body's own conversion to EPA and DHA sufficient to keep levels stable over years. The same body describes low-dose algae-based DHA supplements as available for those with increased needs, such as pregnancy or lactation, or reduced conversion ability, rather than as a default for everyone. Iodine sits on firmer ground as a real risk: both the Academy and the British Dietetic Association flag it, and the BDA is explicit that because excess iodine is also unhealthy, anyone considering a supplement should speak to a dietitian rather than estimate a dose alone. Iron and zinc land the other way. The Academy's review found no adverse health consequences in adult vegetarians attributable to lower zinc status, and that non-heme iron absorption adapts substantially over time in people eating a varied plant diet, evidence that does not support routine supplementation for either.
Vitamin D: the shortfall that isn't really a vegan story
Vitamin D status depends mainly on sunlight exposure, latitude, season, and skin coverage, not diet, according to the Academy of Nutrition and Dietetics, and the Academy recommends supplements when sun exposure and fortified foods aren't enough, especially for older adults, as a general population recommendation rather than a vegan-specific one. The vegan-relevant detail is narrower: vitamin D3 (cholecalciferol) in supplements and fortified foods is frequently sourced from lanolin in sheep's wool, so a vegan checking a label needs to look for D2 (ergocalciferol) or lichen-derived D3 specifically, a labeling question more than a nutritional one.
When this page genuinely isn't enough
Pregnancy, breastfeeding, infancy, older age, a restrictive diet layered on top of veganism, or an existing diagnosis all change these answers in ways a general page cannot responsibly cover. A blood test, not a guess from an ingredient panel, is what tells you whether your own B12, iron, or vitamin D status needs attention, and a registered dietitian or doctor is positioned to weigh your actual levels against your actual life, which this page is not.