The nutrients most often missing in vegan diets are vitamin B12, vitamin D, the long-chain omega-3s EPA and DHA, iron, zinc, calcium and iodine, with protein worth planning but rarely short. Vitamin B12 is the one vegans must get from fortified foods or a supplement, because plants do not naturally contain it. The others can usually be covered with fortified foods, well-chosen plant foods and, where needed, a targeted supplement.
Key Takeaways
- Vitamin B12 is not naturally present in plant foods. The Academy of Nutrition and Dietetics says vegans need a reliable source, such as fortified foods or supplements.
- A review of 141 studies found that vegans and vegetarians generally had lower intake and status of vitamin B12, vitamin D, iron, zinc, iodine and calcium than meat-eaters, and lower EPA and DHA intake.
- Plants supply the omega-3 ALA, but the body converts less than 15% of it to EPA and DHA. Algal oil supplements provide DHA directly.
- Vegetarians need about 1.8 times as much iron as meat-eaters, because plant iron is absorbed less well.
- Iodine is low in most plant foods; iodized salt or a measured supplement is more reliable than seaweed, whose iodine varies widely.
- Protein intake in plant-based eaters was lower than in meat-eaters but still within recommended levels.
Evidence grade: Strong. Based on established NIH reference values, an Academy of Nutrition and Dietetics position paper, and a systematic review of 141 studies comparing nutrient intake and status in plant-based eaters and meat-eaters.
Can a Vegan Diet Cover Every Essential Nutrient?
Yes, with planning. The Academy of Nutrition and Dietetics states that appropriately planned vegetarian diets, including vegan diets, are healthful and nutritionally adequate for all stages of life, including pregnancy, childhood, older age and for athletes. The key words are "appropriately planned." Removing animal foods also removes the main natural sources of a few nutrients, so those need a deliberate replacement.
A 2021 systematic review of 141 studies compared plant-based eaters with meat-eaters. Plant-based eaters took in more fiber, folate, vitamin C, vitamin E and magnesium, but their intake and status of vitamin B12, vitamin D, iron, zinc, iodine and calcium were generally lower. Vegans had the lowest B12, calcium and iodine intakes. Every eating pattern, including meat-based diets, had some gaps, so the lesson is planning. The authors work for a company that sells fortified foods and supplements.
The Nutrients to Plan For at a Glance
| Nutrient | Adult daily target (NIH) | Vegan food and fortified sources | Why vegans run short |
|---|---|---|---|
| Vitamin B12 | 2.4 mcg | Fortified nutritional yeast (about 8 to 24 mcg per quarter cup, check the label), fortified breakfast cereals | Natural sources are limited to animal foods |
| Vitamin D | 15 mcg (600 IU); 20 mcg (800 IU) over 70 | Fortified soy, almond and oat milks (2.5 to 3.6 mcg per cup), UV-exposed mushrooms, fortified cereals | Few foods contain it naturally; most are animal foods |
| Omega-3s | ALA: 1.6 g (men), 1.1 g (women) | Flaxseed oil (7.3 g ALA per tbsp), chia seeds (5.1 g per oz), walnuts (2.6 g per oz); algal oil for DHA | EPA and DHA come mainly from seafood; ALA converts poorly |
| Iron | 8 mg (men, women 51+), 18 mg (women 19 to 50); about 1.8 times higher for vegetarians | Fortified cereals, white beans (8 mg per cup), lentils, firm tofu and cooked spinach (about 3 mg per half cup) | Plant (nonheme) iron is absorbed less well |
| Zinc | 11 mg (men), 8 mg (women) | Fortified cereals, cooked oats (2.3 mg per cup), pumpkin seeds (2.2 mg per oz), lentils | Phytates in legumes and grains reduce absorption |
| Calcium | 1,000 mg; 1,200 mg for women 51+ and everyone 71+ | Calcium-fortified orange juice and soymilk (about 300 to 350 mg per cup), calcium-set firm tofu (253 mg per half cup), kale, bok choy | Dairy is the main source in most diets |
| Iodine | 150 mcg | Iodized salt (78 mcg per quarter teaspoon), nori and other seaweeds (highly variable) | Seafood, eggs and dairy are the main sources; plant milks contain little |
| Protein | Varies with body size | Beans, lentils, chickpeas, tofu, tempeh, quinoa, nuts and seeds | Rarely short; intake is usually within recommendations |
Vitamin B12: The One Nutrient Vegans Must Supplement or Get From Fortified Foods
Vitamin B12 is needed for healthy red blood cell formation, DNA synthesis and normal nervous system function. The NIH Office of Dietary Supplements (ODS) explains that natural food sources of B12 are limited to animal foods, so vegans, and to a lesser degree vegetarians, are more likely to run low. Fortified foods and B12 supplements substantially reduce that risk. The Academy of Nutrition and Dietetics puts it simply: vegans need a reliable source of B12, such as fortified foods or supplements.
Fortified nutritional yeast and fortified cereals are well-absorbed sources, but amounts vary by brand, so read the label. Absorption from a single dose drops above 1 to 2 mcg, which is why supplements often contain far more than the 2.4 mcg target. No upper limit has been set for B12 because of its low potential for toxicity.
Breastfed infants of vegan mothers with low B12 are especially vulnerable, so B12 needs extra attention during pregnancy and breastfeeding. For forms and absorption, see our vitamin B12 guide.
Vitamin D
Vitamin D supports calcium absorption and normal bone maintenance. Few foods contain it naturally, and most that do are animal foods, such as fatty fish and egg yolks. ODS notes that low vitamin D intake is more common in people who follow vegan diets. Sun exposure helps, but it varies with season, latitude, skin tone and sunscreen use.
Plant-based options include vitamin D-fortified soy, almond and oat milks, which supply about 2.5 to 3.6 mcg per cup, and mushrooms exposed to UV light. Supplements come as vitamin D2, made from yeast, or vitamin D3, which is usually made from lanolin in sheep's wool. An animal-free vitamin D3 made from lichen is also available, so vegans who want D3 should check the source with the manufacturer.
Omega-3s: ALA From Plants, EPA and DHA From Algae
There are three main omega-3s. ALA is found in plants and is essential, which means you must get it from food. EPA and DHA are the long-chain forms found mainly in fish, but fish get them from microalgae at the base of the marine food chain. The body can turn ALA into EPA and DHA, but ODS reports the conversion is very limited, at less than 15%.
Flaxseed oil, chia seeds and walnuts cover the ALA target easily (see the table). For DHA and EPA, algal oil supplements usually provide around 100 to 300 mg of DHA, and some add EPA. A small study found DHA from algal oil was absorbed as well as DHA from cooked salmon. Plant-based eaters in the 2021 review had lower EPA and DHA intakes than meat-eaters. Read more in our guide to the benefits of omega-3 fatty acids.
Iron
Iron is part of hemoglobin, the protein that carries oxygen in red blood cells. Plants contain only nonheme iron, which is absorbed less well than the heme iron in meat. ODS estimates iron absorption at about 14% to 18% from mixed diets and 5% to 12% from vegetarian diets. For that reason, the iron requirement for vegetarians is about 1.8 times higher than for people who eat meat.
Good vegan sources include fortified breakfast cereals, white beans, lentils, firm tofu and cooked spinach. Vitamin C enhances nonheme iron absorption, so pairing beans or lentils with peppers, tomatoes or citrus is a simple habit. Phytates in grains and beans, and certain polyphenols in some plant foods, reduce absorption, which is part of why variety and vitamin C pairings help. Our article on iron and energy levels covers why iron matters for feeling energetic.
Zinc
Zinc is needed by hundreds of enzymes and supports normal immune function, protein synthesis and wound healing. ODS lists people who follow vegetarian or vegan diets among those more likely to have low zinc intake, because legumes and whole grains contain phytates that bind zinc. Soaking beans, grains and seeds for several hours before cooking, and eating fermented foods may improve zinc absorption. Fortified cereals, oats, pumpkin seeds and lentils are useful sources.
Calcium
Calcium makes up much of the structure of bones and teeth. People who avoid dairy, including vegans, are more likely to have low calcium intake. In the 2021 review, vegans had the lowest calcium intake and lower bone mineral density than other groups.
Calcium-fortified orange juice and soymilk provide about 300 to 350 mg per cup, and calcium-set firm tofu provides about 253 mg per half cup. Kale, bok choy and turnip greens add more. Spinach contains calcium, but its oxalic acid limits how much is absorbed, so it is not a reliable calcium source. If you use a supplement, absorption is highest with doses of 500 mg or less at a time.
Iodine
Iodine is needed to make thyroid hormones, which regulate metabolism. The best sources are seafood, eggs and dairy, while most fruits and vegetables are poor sources, and soy and almond beverages contain little. ODS notes that vegans and people who eat few dairy products, seafood and eggs might not get enough.
A quarter teaspoon of iodized salt provides about 78 mcg, about half the 150 mcg adult target. Sea salt and most salt in processed foods are not iodized. Seaweed is a rich source, but its iodine content ranges from 16 to nearly 3,000 mcg per gram, so it is hard to dose. Too much iodine can cause problems, so stay under the 1,100 mcg daily upper limit. Learn more in our article on iodine and thyroid function.
Protein
Protein is the nutrient people worry about most, yet it is rarely the real gap. In the 2021 review, protein intake in plant-based eaters was lower than in meat-eaters but well within recommended levels. Beans, lentils, chickpeas, tofu, tempeh, quinoa, nuts and seeds are good sources. Eating a variety of them across the day, with enough total food, is the simplest approach.
Building a Day That Covers the Gaps
- Every day: a B12-fortified food or a B12 supplement, and fortified plant milk or juice for vitamin D and calcium.
- At most meals: legumes or tofu for protein, iron and zinc, with a vitamin C food for better iron absorption.
- In the pantry: ground flaxseed, chia or walnuts for ALA, pumpkin seeds for zinc, and iodized salt for cooking. Consider algal oil for DHA and EPA.
Where a Multivitamin Fits
A multivitamin can help cover several nutrients at once, but check what it contains and whether it suits a vegan diet. OPA Women's Daily Multivitamin lists vitamin B12 in its B-vitamin complex, along with 10 mcg of vitamin D3, 15 mg of zinc, 50 mg of magnesium, 150 mg of vitamin C and 13.5 mg of vitamin E per 2-capsule serving, plus botanical, immune and antioxidant blends. Its 10 mcg of vitamin D3 is two-thirds of the 15 mcg adult target, and its 15 mg of zinc is above the 8 mg target for women but well under the 40 mg upper limit. The product listing does not state the B12 amount, does not list iron, iodine, calcium or omega-3s, and does not say whether the capsule or the vitamin D3 is animal-free. It lists no fish or shellfish ingredients. If you follow a strict vegan diet, check the full label or ask before buying.
Safety and Interactions
Getting these nutrients from food is safe. With supplements, more is not better, and several have upper limits set by the National Academies:
- Vitamin D: upper limit 100 mcg (4,000 IU) a day for adults. Orlistat, statins, steroids and thiazide diuretics can affect it.
- Iron: upper limit 45 mg a day. High doses can upset the stomach. Iron interacts with levodopa and levothyroxine, and acid-reducing medicines can lower iron absorption.
- Zinc: upper limit 40 mg a day. Taking 50 mg or more for weeks can lower copper absorption. Zinc interacts with quinolone and tetracycline antibiotics and penicillamine, and some diuretics increase zinc loss.
- Calcium: upper limit 2,500 mg a day for ages 19 to 50 and 2,000 mg from age 51. Calcium supplements can interact with levothyroxine, lithium, dolutegravir and quinolone antibiotics.
- Iodine: upper limit 1,100 mcg a day. Excess iodine can disrupt thyroid hormone production in susceptible people. Iodine supplements can interact with antithyroid medicines, ACE inhibitors and potassium-sparing diuretics.
- Vitamin B12: no upper limit. Metformin and acid-reducing medicines such as proton pump inhibitors can lower B12 absorption.
- Omega-3s: high-dose fish oil might affect clotting time with warfarin, although most research at 3 to 6 g a day found no significant effect.
If you take any of these medicines, are pregnant or breastfeeding, or are planning a vegan diet for a child, talk to your doctor, pharmacist or a registered dietitian first.
Frequently Asked Questions
What are the most common nutrient gaps in a vegan diet?
Vitamin B12, vitamin D, EPA and DHA, iron, zinc, calcium and iodine. Of these, B12 is the one vegans cannot get from unfortified plant foods.
Do vegans need to take supplements?
Vegans need a reliable B12 source, either fortified foods or a supplement. Vitamin D, iodine and algal omega-3s are often worth considering too, depending on diet, sun exposure and life stage.
How can vegans get enough protein?
Eat a variety of legumes, soy foods such as tofu and tempeh, quinoa, nuts and seeds, and eat enough total food. Research shows plant-based eaters usually meet protein recommendations.
How can vegans absorb more iron from plant foods?
Pair iron-rich foods like beans, lentils, tofu and fortified cereals with vitamin C foods such as peppers, tomatoes or citrus. Vitamin C enhances the absorption of plant iron.
Is seaweed a good way for vegans to get iodine?
Seaweed is rich in iodine, but the amount varies so widely that it is hard to dose. Iodized salt or a measured supplement is more predictable.
Sources
- NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. Updated 2025.
- NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. Updated 2025.
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. Updated 2025.
- NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. Updated 2025.
- NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. Updated 2026.
- NIH Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals. Updated 2026.
- NIH Office of Dietary Supplements. Iodine: Fact Sheet for Health Professionals. Updated 2024.
- Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016.
- Neufingerl N, Eilander A. Nutrient Intake and Status in Adults Consuming Plant-Based Diets Compared to Meat-Eaters: A Systematic Review. Nutrients. 2021.
Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.
Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: · How OPA researches and writes
