Vegans need to pay close attention to a handful of nutrients that are either absent from plant foods or poorly absorbed from them. Vitamin B12 is the most critical, with over half of vegans who don’t supplement showing signs of deficiency. Beyond B12, the shortlist includes vitamin D, omega-3 fatty acids, iron, zinc, calcium, iodine, choline, and vitamin K2. Most of these can be managed through smart food choices, but a few genuinely require supplements.
Vitamin B12: The Non-Negotiable Supplement
No plant food naturally contains a reliable amount of B12. This is the one nutrient every vegan must supplement, full stop. A study of Czech vegans found that 52.9% of those who didn’t use B12 supplements were deficient, compared to just 5.6% of those who supplemented regularly. Even irregular supplementation left nearly 18% deficient.
B12 is essential for nerve function and red blood cell production. Deficiency develops slowly, sometimes over years, and early symptoms like fatigue and brain fog are easy to dismiss. Left untreated, it can cause irreversible nerve damage.
The two most common supplement forms are cyanocobalamin and methylcobalamin. Cyanocobalamin is synthetic, more stable, and cheaper. Your body absorbs it slightly better (about 49% of a small dose versus 44% for methylcobalamin), though methylcobalamin may be retained in the body more effectively. In practice, the difference is small. Cyanocobalamin is the more widely recommended option for vegans because of its stability and the larger body of research behind it. Fortified plant milks, nutritional yeast, and breakfast cereals can contribute, but most nutrition experts consider them insufficient as a sole source.
Vitamin D: Sunshine Isn’t Always Enough
Your skin makes vitamin D from sunlight, but if you live above about 37 degrees latitude (roughly the line from San Francisco to Richmond, Virginia), you won’t produce meaningful amounts during winter months. Darker skin, sunscreen use, and indoor lifestyles reduce production further.
Two forms exist in supplements: D2 and D3. Vitamin D3 is more effective at raising blood levels than D2. Historically, D3 came only from animal sources like lanolin or fish oil, but lichen-derived D3 is now widely available and fully vegan. Look for “vegan D3” or “lichen-derived D3” on the label. Fortified plant milks typically contain D2, which works but requires higher doses to achieve the same result.
Omega-3s: The Conversion Problem
Plant foods like flaxseeds, chia seeds, and walnuts are rich in ALA, a short-chain omega-3. Your body needs to convert ALA into the long-chain forms EPA and DHA, which support brain and heart health. The problem is that conversion is inefficient. In men, roughly 8% of ALA converts to EPA and somewhere between 0% and 4% converts to DHA. Women do better, converting about 21% to EPA and 9% to DHA, likely due to the influence of estrogen.
Those conversion rates mean that even generous ALA intake may not produce enough DHA, particularly for men. Algae-based DHA supplements bypass the conversion issue entirely. Algae is where fish get their omega-3s in the first place, so going straight to the source is both effective and vegan.
Iron: Absorption Matters More Than Quantity
Plants contain only non-heme iron, which your body absorbs less efficiently than the heme iron found in meat. But the real issue isn’t how much iron is on your plate. It’s what you eat alongside it.
Polyphenols in tea, coffee, and cocoa dramatically reduce iron absorption. Black tea inhibits absorption by 79% to 94%. Peppermint tea blocks 84%, and cocoa cuts it by 71%. Even at lower concentrations, beverages with 20 to 50 milligrams of polyphenols per serving reduce absorption by 50% to 70%. Vitamin C, on the other hand, is the most powerful enhancer of non-heme iron absorption. Pairing iron-rich foods like lentils, chickpeas, or spinach with a source of vitamin C (bell peppers, citrus, tomatoes) at the same meal makes a significant difference. Drinking tea or coffee between meals rather than during them is one of the simplest changes you can make.
Zinc: Phytates Change Your Target
Legumes, whole grains, nuts, and seeds are good zinc sources on paper, but they’re also high in phytates, compounds that bind to zinc and reduce absorption. This means vegans need more zinc than omnivores to absorb the same amount.
The German, Austrian, and Swiss nutrition societies now set zinc recommendations based on phytate intake. For a high-phytate diet (typical of many vegan eating patterns), the recommended intake rises to 16 mg per day for men and 10 mg per day for women, compared to 11 mg and 7 mg on a low-phytate diet. That’s roughly a 45% increase. Soaking, sprouting, and fermenting grains and legumes reduces their phytate content and improves zinc availability.
Calcium: Plant Sources Can Compete
Dairy products have a calcium absorption rate of about 30%. Plant foods like leafy greens actually have higher bioavailability than dairy, meaning your body absorbs a greater percentage of the calcium they contain. The catch is that most plant foods contain less total calcium per serving, so you need to eat more of them or choose fortified options.
Low-oxalate greens are your best bet. Kale, bok choy, and broccoli are excellent choices. Spinach, despite being calcium-rich on paper, is high in oxalates that bind calcium and make it largely unavailable. Fortified plant milks, calcium-set tofu, and fortified orange juice can fill the gap. If you rely heavily on fortified plant milk, shake the carton well because calcium tends to settle at the bottom.
Iodine: Easy to Overlook, Easy to Fix
Iodine is essential for thyroid function, and vegans who don’t use iodized salt or eat seaweed are at risk of getting too little. Dairy is a significant iodine source for omnivores (largely because of iodine-based sanitizers used in dairy farming), so dropping dairy removes a major contributor.
Seaweed is the most concentrated plant source. Dried nori provides about 116 micrograms per two-tablespoon serving, which is close to the adult recommendation of 150 micrograms per day. Kelp, however, can contain wildly excessive amounts and may push you past safe upper limits if eaten regularly. The simplest approach is using iodized salt in cooking or taking a supplement with a controlled dose. Many vegan multivitamins include iodine for this reason.
Choline: The Overlooked Nutrient
Choline supports liver function, brain development, and muscle movement. The adequate intake is 550 mg per day for men and 425 mg per day for women. Most people, vegan or not, don’t get enough, but plant-based diets make it harder because the richest sources are eggs and liver.
The best vegan source is roasted soybeans, with 107 mg per half cup. Cruciferous vegetables contribute smaller amounts: Brussels sprouts provide 32 mg per half cup, broccoli 31 mg, and cauliflower 24 mg. Reaching the target through food alone requires deliberate effort, eating generous portions of soy products and cruciferous vegetables daily. Quinoa, beans, and peanuts also contribute. If your diet doesn’t consistently include these foods, a choline supplement is worth considering, especially during pregnancy when demands increase to 450 mg per day.
Vitamin K2: Fermented Foods or Supplements
Vitamin K1 is abundant in leafy greens, but vitamin K2 is a different story. K2 helps direct calcium into bones and teeth rather than arteries, and it’s found primarily in animal products and fermented foods. The richest vegan source by a wide margin is natto, a Japanese fermented soybean dish that delivers about 150 micrograms per tablespoon, roughly twice the recommended intake. Sauerkraut contains a much smaller amount at 2.75 micrograms per half cup.
If you enjoy natto, your K2 needs are easily covered. If you don’t (and many people find its sticky texture and strong flavor challenging), a vegan K2 supplement in the MK-7 form, typically derived from fermented chickpeas or natto extract, is the most practical alternative.
Putting It Together
Not every nutrient on this list requires a pill. A well-planned vegan diet rich in legumes, leafy greens, nuts, seeds, fortified foods, and fermented soy can cover most of the bases. The nutrients that almost always require supplementation are B12 (universally), vitamin D (for most people, especially in winter), and omega-3 DHA (particularly for men). The rest depend on your eating habits. If you eat plenty of calcium-fortified foods, use iodized salt, soak your grains, and pair iron-rich meals with vitamin C, you can meet most targets through food. A well-formulated vegan multivitamin can serve as a safety net for the gaps that are harder to track day to day.