Vegans need to pay close attention to seven nutrients that are either absent from plant foods or significantly harder to absorb from them: vitamin B12, omega-3 fatty acids, iron, calcium, vitamin D, zinc, and iodine. Selenium and protein round out the list, though they’re easier to get with minimal planning. None of these gaps are dealbreakers, but ignoring them can lead to real deficiencies over months or years.
Vitamin B12
This is the one non-negotiable supplement for vegans. Vitamin B12 does not exist in any reliable, unfortified plant food. The recommended daily intake for adults is 2.4 mcg, which you can get from about two tablespoons of fortified nutritional yeast. But relying on fortified foods alone is risky because intake varies day to day. An oral supplement of at least 250 mcg daily is a more reliable strategy, and many health professionals recommend 500 to 1,000 mcg several times per week.
Deficiency can take years to develop because your liver stores B12, but when it hits, the consequences are serious. Early signs include fatigue, weakness, lightheadedness, and a sore tongue. The more concerning effects are neurological: tingling or numbness in the hands and feet, memory problems, mood changes, difficulty walking, and impaired concentration. These nerve symptoms can appear months before blood tests show anemia, which means you can be deficient without the “classic” signs showing up in routine bloodwork. Long-term deficiency raises levels of a compound called homocysteine, which is linked to neurodegenerative disease.
Omega-3 Fatty Acids
Plant foods like flaxseeds, chia seeds, hemp seeds, and walnuts provide a type of omega-3 called ALA, but your body needs to convert ALA into two other forms, EPA and DHA, to get the full anti-inflammatory and brain-health benefits. That conversion is inefficient. In men, only about 8% of ALA converts to EPA and somewhere between 0% and 4% converts to DHA. Women do somewhat better, converting roughly 21% to EPA and 9% to DHA, likely due to the influence of estrogen.
These conversion rates mean that even if you eat plenty of flax and walnuts, you may still fall short on DHA, which is the form most important for brain and eye health. An algae-based DHA supplement (typically 250 to 500 mg per day) is the most direct solution. Algae is where fish get their DHA in the first place, so it’s effective and entirely plant-derived.
Iron
Plants contain only non-heme iron, which your body absorbs at much lower rates than the heme iron in meat. The good news is that vitamin C dramatically improves absorption. When researchers increased vitamin C from 25 mg to 1,000 mg alongside a meal containing non-heme iron, absorption jumped from 0.8% to 7.1%. That’s nearly a ninefold increase. The catch: the vitamin C needs to be eaten at the same meal. Taking it hours before has little effect.
In practical terms, this means pairing iron-rich foods like lentils, chickpeas, tofu, spinach, and fortified cereals with a source of vitamin C. Squeeze lemon on your lentil soup, add bell peppers to a stir-fry with tofu, or have a glass of orange juice with your oatmeal. Coffee and tea contain compounds that inhibit iron absorption, so spacing those away from iron-rich meals helps too.
Calcium
Dairy is the most concentrated dietary source of calcium, but it’s not necessarily the most absorbable. Cruciferous vegetables actually outperform milk when it comes to absorption rates. Your body absorbs about 52% to 53% of the calcium in kale and bok choy, compared to roughly 46% from milk. Broccoli comes in at about 48%.
The limitation is volume. A cup of cooked kale has far less total calcium than a glass of milk, so you’d need to eat generous servings to match the overall amount. Fortified plant milks, fortified orange juice, tofu made with calcium sulfate, and white beans help fill the gap. Aim for at least 1,000 mg per day from a combination of these sources. One important note: spinach is high in calcium on paper, but it contains oxalates that block most of its absorption, so don’t count on it as a primary source.
Vitamin D
Vitamin D is tricky for everyone, not just vegans, because few foods naturally contain meaningful amounts. Your skin produces it from sunlight, but that depends on latitude, season, skin tone, and sunscreen use. Most people in northern climates fall short during winter months regardless of diet.
The standard vitamin D3 supplement comes from lanolin (sheep wool), but vegan D3 sourced from lichen is widely available and research suggests it’s well absorbed. Vitamin D2, derived from mushrooms exposed to UV light, is another plant-based option, though D3 is generally considered more effective at raising blood levels. A daily supplement of 1,000 to 2,000 IU is a reasonable starting point for most adults, though your ideal dose depends on your current blood levels. Fortified plant milks and cereals contribute small amounts but rarely enough on their own.
Zinc
Plant-based zinc sources include legumes, whole grains, nuts, and seeds, but they all contain phytates, compounds that bind to zinc and reduce how much your body can absorb. Vegans tend to need up to 50% more zinc than the general recommendation because of this lower bioavailability.
Simple food preparation techniques make a real difference. Soaking and sprouting legumes reduces their phytate content by roughly 27% to 35%, and the bioavailability of zinc can increase substantially as a result. In one study on faba beans, sprouting improved zinc availability by 49% to 59% compared to untreated beans. Fermenting grains (as in sourdough bread) also breaks down phytates. Toasting nuts and seeds helps to a lesser degree. Pumpkin seeds, cashews, chickpeas, and oats are among the best plant sources.
Iodine
Iodine is easy to overlook because the main dietary sources for most people are dairy (from iodine-containing sanitizers used on equipment) and iodized salt. If you don’t cook with iodized salt regularly, you may get very little.
Seaweed is the most concentrated plant source, but the amounts vary wildly. Commercially available seaweeds range from 16 mcg per gram to nearly 3,000 mcg per gram. Nori, the type used in sushi, is on the more moderate end, with about 116 mcg in two tablespoons of dried flakes. Kelp, on the other hand, can easily push you over the tolerable upper limit of 1,100 mcg per day if you eat even a small portion. The safest approach is to use iodized salt consistently or take a supplement providing 150 mcg, which is the adult recommended intake.
Selenium
Selenium is found in whole grains, legumes, and sunflower seeds, but the amounts depend heavily on soil conditions where the food was grown. Brazil nuts are by far the richest source, containing 68 to 91 mcg per single nut. The adult recommendation is 55 mcg per day, so just one Brazil nut covers it. But the tolerable upper limit is 400 mcg, meaning eating four or five nuts a day could push you into excess. One to two Brazil nuts daily is a simple, effective strategy. If you don’t like them, a basic multivitamin usually covers it.
Protein
Getting enough total protein on a vegan diet is straightforward if you eat a reasonable variety of legumes, whole grains, soy products, nuts, and seeds. The outdated idea of carefully “combining” proteins at every meal has largely been set aside. What matters is eating a mix of protein sources throughout the day.
The reason variety matters is that different plant foods are low in different essential amino acids. Grains tend to be low in lysine, while legumes tend to be low in methionine. Eating both over the course of a day gives your body the full set of building blocks it needs. Soy is the exception: tofu, tempeh, and edamame contain all essential amino acids in adequate proportions, making them especially useful staples.
A Practical Supplement Strategy
You don’t need a cabinet full of bottles. At minimum, every vegan should supplement vitamin B12 (at least 250 mcg daily) and vitamin D (1,000 to 2,000 IU daily). An algae-based omega-3 supplement covering DHA is a strong addition. Beyond that, whether you need separate supplements for iron, zinc, calcium, iodine, or selenium depends on how well your diet covers them. A well-planned vegan diet built around legumes, whole grains, leafy greens, nuts, seeds, fortified plant milks, and nutritional yeast can cover most of these nutrients through food alone, with B12 and vitamin D as the consistent exceptions.