A well-planned vegan diet covers most nutritional bases, but several nutrients are harder to get without animal products. The ones that matter most are vitamin B12, omega-3 fatty acids (specifically EPA and DHA), zinc, calcium, iodine, choline, and the amino acid lysine. Some of these require supplements, others just require deliberate food choices.
Vitamin B12
This is the one non-negotiable supplement for vegans. No plant food naturally contains meaningful amounts of B12, and your body needs it for nerve function and red blood cell production. The recommended daily amount for adults is 2.4 mcg (2.6 mcg during pregnancy, 2.8 mcg while breastfeeding).
You can get B12 from fortified nutritional yeast, fortified plant milks, and fortified cereals, but relying on these alone makes it easy to fall short. A B12 supplement is the most reliable approach. Deficiency develops slowly, sometimes over years, which makes it deceptive. By the time symptoms appear (numbness, fatigue, cognitive fog), nerve damage may already be underway.
Omega-3 Fatty Acids
Your body needs two specific omega-3s that are difficult to get from plants: EPA and DHA. These are critical for brain health, heart function, and managing inflammation. Flaxseeds, chia seeds, and walnuts provide ALA, a precursor omega-3, but humans convert ALA into EPA and DHA at a rate of only about 5% to 8%. That conversion drops another 40% to 50% if your diet is high in omega-6 fats, which are abundant in vegetable oils like sunflower and corn oil.
For most vegans, a microalgae-based omega-3 supplement is the practical solution. Algae oil provides EPA and DHA directly, bypassing the conversion problem entirely. A dose of 100 to 300 mg of DHA per day is a common target, with pregnant and breastfeeding women aiming for the higher end of 200 to 300 mg combined EPA and DHA.
Zinc and the Phytate Problem
Zinc is involved in immune function, wound healing, and protein synthesis. The standard recommendation is 11 mg per day for men and 8 mg for women, but these numbers assume a mixed diet. Vegan diets are rich in phytate, a compound found in whole grains, legumes, nuts, and seeds that binds to zinc and reduces how much your body absorbs.
The impact is substantial. Modeling research published in The Journal of Nutrition found that consuming 1,000 mg of dietary phytate per day roughly doubles the amount of zinc you need, and 2,000 mg triples it. At 2,000 mg of daily phytate, a man’s effective zinc requirement jumps from 11 mg to around 32 mg, and a woman’s from 8 mg to about 24 mg. People who eat large amounts of unrefined grains and legumes (which describes many vegans) can easily reach 2,000 to 2,500 mg of phytate daily.
You can reduce phytate’s effects through food preparation. Soaking beans and grains before cooking, sprouting seeds, and fermenting foods like sourdough bread all break down phytate and free up more zinc. Pairing zinc-rich foods with something acidic, like lemon juice, also helps. Good vegan sources include pumpkin seeds, lentils, chickpeas, cashews, and tofu.
Calcium and Bone Health
Getting enough calcium on a vegan diet is entirely doable, but which plant foods you choose matters more than you might expect. The issue isn’t just how much calcium a food contains on paper. It’s how much your body actually absorbs.
Low-oxalate greens are calcium superstars. Bok choy has a fractional absorption rate of about 52%, broccoli around 48%, and kale about 41%. Compare that to fortified plant milk at roughly 36%, or dairy milk at about 45%. So cup for cup, bok choy and broccoli actually deliver calcium to your bloodstream more efficiently than fortified soy milk. High-oxalate greens, on the other hand, are nearly useless for calcium. Spinach and rhubarb have absorption rates below 10%, meaning your body gets almost nothing from the calcium they contain.
Fortified plant milks are still a convenient daily source, and tofu made with calcium sulfate is another strong option. The key is eating low-oxalate greens regularly and not assuming that any green vegetable is a good calcium source.
Iodine and Thyroid Function
Iodine is essential for thyroid hormones that regulate metabolism, and vegan diets can be very low in it. Dairy and seafood are the main sources in most Western diets, so removing them creates a gap. The recommended daily intake for adults is 150 mcg.
Seaweed can fill this gap, but the iodine content varies wildly by type. Nori, the kind wrapped around sushi, contains about 18 mcg per gram. Wakame has roughly 172 mcg per gram. Kombu contains a staggering 2,267 mcg per gram on average, which means a single gram delivers more than 15 times the daily recommendation and pushes well past safe limits. Eating kombu regularly without measuring portions is a real risk for iodine toxicity, which can suppress thyroid function just like deficiency can.
The safest and most consistent approach is a supplement providing 150 mcg of iodine, or using iodized salt (about half a teaspoon covers the daily need). If you eat seaweed, stick with nori and use wakame sparingly.
Choline
Choline doesn’t get much attention, but it’s essential for liver function, brain development, and cell membrane integrity. The adequate intake is 550 mg per day for men and 425 mg for women. Most people fall short regardless of diet, but vegans face a steeper challenge because the richest sources are eggs, liver, and fish.
Plant foods that contribute meaningful amounts include shiitake mushrooms (58 mg per half cup), wheat germ (51 mg per ounce), Brussels sprouts (32 mg per half cup), and almonds (15 mg per ounce). Cruciferous vegetables and beans collectively provide roughly 10% of the daily requirement. Soybeans and quinoa also contribute, but reaching 425 to 550 mg from plants alone takes real effort. If your diet doesn’t consistently include multiple choline-containing foods every day, a supplement is worth considering.
Lysine and Protein Quality
Total protein is rarely a problem on a vegan diet, but lysine, a specific essential amino acid, can be. Lysine requirements sit around 35 mg per kilogram of body weight per day, which works out to about 2,450 mg for a 70 kg (154 lb) person. Grains, which form the backbone of many plant-based diets, are notably low in lysine.
The fix is straightforward: eat legumes. Lentils, chickpeas, black beans, and soy products like tofu and tempeh are all rich in lysine. Seitan (wheat gluten) is high in protein but very low in lysine, so it shouldn’t be your primary protein source. Pistachios, pumpkin seeds, and quinoa also contribute. You don’t need to combine proteins at every meal, but your overall daily diet should include legumes or soy at least once or twice.
Selenium
Selenium acts as an antioxidant and supports thyroid and immune function. The daily recommendation is 55 mcg for adults, with an upper limit of 400 mcg. For vegans, Brazil nuts are uniquely powerful. The average selenium concentration in Brazil nuts is about 31 mcg per gram, though it varies enormously depending on where the nuts were grown, ranging from 8 to 83 mcg per gram.
A single Brazil nut weighs roughly 4 to 5 grams, putting its selenium content anywhere from 32 to over 400 mcg. Eating just one or two Brazil nuts per day is typically enough to meet your selenium needs. Eating a handful daily, however, can push you past the upper limit and cause selenosis, a toxicity syndrome marked by brittle nails, hair loss, and garlic breath. This is one nutrient where more is genuinely dangerous, so keep it to one to three nuts per day.
Putting It All Together
Three nutrients realistically require supplements for most vegans: B12, omega-3 DHA from algae oil, and iodine (unless you’re careful with iodized salt). Choline and selenium may need supplementation depending on your food choices. Zinc, calcium, and lysine are achievable through food, but only with deliberate planning, especially soaking and sprouting to reduce phytate and choosing low-oxalate greens for calcium.
A simple daily checklist: take B12 and algae-based omega-3 supplements, use iodized salt or an iodine supplement, eat legumes or soy for lysine, include low-oxalate greens or fortified plant milk for calcium, eat one to two Brazil nuts for selenium, and make sure mushrooms, soy, or cruciferous vegetables show up regularly for choline. None of this is complicated once it becomes routine.