Supplements for vegetarians and vegans: what is lacking in a plant-based diet and how to supplement

A well-planned plant-based diet can be healthy and complete – but "well-planned" is the key phrase. Without conscious supplementation of several nutrients that a plant-based diet does not provide in sufficient amounts, you risk serious deficiencies that develop over years, often without clear symptoms – until the damage becomes irreversible. This article describes the six most important nutrients that every vegan and vegetarian should pay attention to, with specific doses, forms, and tips on how to avoid common supplementation pitfalls.

KEY INFORMATION
• Vitamin B12 is the only nutrient for which supplementation is absolutely mandatory on a vegan diet – there are no sources in plant products (Pawlak et al., Nutrition Reviews, 2013).
• The conversion of ALA (omega-3 from flax and hemp) to DHA in humans is less than 5–10% – it does not meet the brain's demand for DHA.
• Non-heme iron from plants is absorbed 5–15 times worse than heme iron from meat – vegetarians have a 1.8 times higher iron requirement according to WHO.
• Iodine is often overlooked by most vegans, yet deficiency is the second most common cause of thyroid dysfunction in Poland.

Vitamin B12 – supplementation is mandatory, not optional

Vitamin B12 (cobalamin) is produced exclusively by microorganisms – not by plants or animals. Animal products contain B12 because animals consume bacteria or are given them in supplements (especially in industrial farming). No plant product – neither seaweed, nor nutritional yeast without fortification, nor tempeh – contains bioavailable B12 in amounts sufficient to meet the daily requirement of an adult. Review by Pawlak et al. (Nutrition Reviews, 2013) showed that 52% of vegans are deficient in B12, and 7% have levels below the clinical deficiency threshold leading to megaloblastic anemia and neuropathy.

B12 deficiency is insidious – the liver stores its reserves for 3–5 years. During this time, symptoms (fatigue, tingling in the limbs, memory disturbances, depression) gradually increase. By the time levels drop to clinically critical, neurological damage may already be partially irreversible. This is not scaremongering – it's pharmacology. Therefore, B12 is the only supplement that vegans cannot "put off for later."

Dosage: two options are clinically equivalent. Opcja 1: 50–100 µg of cyanocobalamin daily in a capsule or tablet. Opcja 2: 1000–2000 µg 2–3 times a week (higher doses are necessary with less frequent intake due to the mechanism of passive absorption). The cyanocobalamin form is the cheapest and most stable. Methylcobalamin is more expensive and less stable, but equally effective. Sublingual B12 sprays work and are convenient for those with difficulty swallowing tablets.

Our observations: Many vegans assume that fortified foods (plant milk, cereals) provide sufficient amounts of B12. In practice, the amounts in fortified products are too small and too variable to replace a supplement. Even with regular consumption of several servings of fortified food daily, it is difficult to reliably meet the 2.4 µg daily requirement – and absorption from food is variable. A supplement provides certainty and costs just a few zlotys a month.

DHA z alg – omega-3 bez ryb

Docosahexaenoic acid (DHA) is a key component of cell membranes in the brain and retina. Fish contain DHA because they eat algae and plankton – it is algae that are the primary source of DHA in the food chain. Alpha-linolenic acid (ALA) from flax, chia, and hemp seeds is a precursor to DHA, but the conversion in humans is dramatically low: badanie Burdge i Calder (Reproduction Nutrition Development, 2005) showed ALA conversion to DHA at levels of 0.5–5% in men and up to 9% in women. This is definitely too little to meet the needs of the brain and heart.

A solution for vegans: algal oil. Available in capsule form, it contains DHA that is biologically identical to fish-derived DHA. Schizochytrium and Nannochloropsis are the most common algal species used to produce vegan DHA – both have good safety and bioavailability documentation. An additional advantage: no risk of mercury and dioxin contamination typical of wild-caught fish oil.

Dosage: 250–500 mg of DHA daily for adults. During pregnancy and breastfeeding: 400–600 mg DHA/d (especially important for the development of the child's brain). It is advisable to take the algal DHA capsule with a meal containing fats – absorption is significantly better with food than on an empty stomach. Store in the refrigerator after opening – omega-3 fatty acids are sensitive to oxidation.

Iron – when to supplement and when not to

Iron in a plant-based diet is non-heme iron (Fe³⁺), which is absorbed significantly worse than heme iron from meat. WHO estimates that vegetarians need 1.8 times more iron daily than meat-eaters – due to lower bioavailability. For women of childbearing age, this means 32 mg/d, for men and postmenopausal women – about 14 mg/d.

It is crucial to test ferritin, not just blood morphology. Ferritin below 30 µg/l indicates depletion of iron stores before anemia appears. With ferritin levels of 30–70 µg/l, it is advisable to focus on a diet rich in non-heme iron (beans, lentils, tofu, pumpkin seeds, amaranth) and strategic pairing with vitamin C. With ferritin below 30 µg/l or symptoms of deficiency (chronic fatigue, hair loss, pallor) – supplementation is indicated.

The form of the supplement matters: iron malate, fumarate, and amino acid chelate are better tolerated by the stomach than iron sulfate, although the latter is cheaper. Never combine iron with coffee, tea, calcium, or zinc supplements – they block absorption. Vitamin C (50–100 mg) or acidic foods (fermented foods, tomatoes) taken together increase absorption threefold.

Vitamin D – deficiency is common regardless of diet

Vitamin D is produced by the skin under the influence of UVB radiation. In Poland, during the months of October to March, skin synthesis is practically zero – deficiency affects 70–80% of the population, regardless of whether someone eats meat or not. But vegans have an additional problem: traditional dietary sources of D3 (fatty fish, egg yolks) are excluded from their diet. EFSA (2016) has established a safe level of supplementation for adults at 4000 IU daily.

Vegans need to pay attention to the form of D3: classic D3 comes from sheep lanolin and is suitable for vegetarians, but not for vegans. Alternative: D3 from lichens (e.g., Cladonia rangiferina) – an identical biochemical form, but 100% plant-based. Vitamin D2 (ergocalciferol) is also vegan, but it is converted to the active form in the body less effectively than D3. For optimal effect, supplement with D3+K2 (menaquinone MK-7, vegan from fermentation) – K2 directs calcium to the bones and prevents its deposition in the arteries.

Calcium – does a plant-based diet provide enough?

Calcium is a controversial topic in the context of a plant-based diet. On one hand, vegans avoid dairy – the main source of calcium in the omnivore diet. On the other hand, legumes, tofu (made with calcium coagulant), almonds, broccoli, and fortified plant drinks can provide plenty of calcium – provided that the diet is well-planned. Review by Davey et al. (Public Health Nutrition, 2003) showed that vegans consume on average 20% less calcium than vegetarians who eat dairy.

The problem with calcium in plants is bioavailability. Calcium oxalate in spinach and Swiss chard blocks calcium absorption from these vegetables almost completely (absorption is only 5%). Tofu with calcium coagulant, broccoli, kale, and fortified plant drinks have significantly higher bioavailability (40–60%). If you eat a varied, well-planned plant-based diet with 100–200 ml of fortified plant milk daily, you probably do not need additional calcium supplementation. If your diet is poorer – a supplementation of 500 mg of calcium (citrate, not carbonate, for better absorption) may be justified.

Cynk i jod – dwa zapomniane mikroelementy

Zinc is a cofactor for over 300 enzymes and is essential for the proper functioning of the immune system, DNA synthesis, and hormonal functions. A plant-based diet is rich in zinc (buckwheat, pumpkin seeds, lentils, tofu), but phytic acid in these products blocks its absorption. Hunt Review (Journal of Nutrition, 2003) showed that vegans need 50% more zinc daily than those on a mixed diet. Soaking, sprouting, and fermenting plant products (sourdough bread, tempeh, pickles) significantly increase zinc bioavailability by reducing phytic acid content.

Zinc supplementation: 10–15 mg/d in the form of citrate or picolinate for vegans. Do not exceed 40 mg/d – excess blocks copper absorption and can lead to a deficiency of this element. Take zinc separately from iron (they compete for the same transporters) and from coffee.

Iodine is a nutrient that vegans completely forget about. Sea fish and seafood are the main dietary sources of iodine for most of the population. Vegans do not eat them. Seaweeds (kelp, nori) contain iodine, but in dramatically varying amounts – from deficiency to toxic excess in one serving. The best solution is iodized salt (used regularly) or a supplement with 150 µg of iodine daily (KI or KIO₃). Iodine deficiency is a major reversible cause of hypothyroidism.

How to plan supplementation on a plant-based diet – the minimum set

Instead of buying dozens of supplements, start with a minimal set that guarantees coverage of critical deficiencies. For a healthy adult vegan, the essential minimum is: vitamin B12 (cyanocobalamin 50–100 µg/d or 1000 µg 2×/week), DHA from algae (250–500 mg/d), and vitamin D3 from lichens (2000–4000 IU/d in winter, 1000 IU in spring and summer – if little time in the sun).

Supplement zinc, iodine, and iron selectively based on blood test results. Regularly measuring ferritin, serum zinc, and TSH (thyroid – iodine marker) allows you to avoid both deficiencies and unnecessary supplementation. Get tested once a year, especially if you have been on a plant-based diet for more than 2 years.

A good source of protein in a plant-based diet – and incidentally zinc – is hemp. Hemp seeds contain 31 g of protein per 100 g, a complete amino acid profile, and about 5 mg of zinc/100 g. They will not replace a supplement, but they are a very good dietary component. Hemp oil provides ALA in a good ratio to LA – it is worth including it as a basic oil for salads.

Read more about supplements supporting immunity in the autumn-winter season – a significant challenge for everyone, including vegans – in the article Supplements for autumn and immunity.

When and how to get routine checks on a plant-based diet?

Supplementation without monitoring is shooting in the dark. A blood count with a smear, ferritin, serum vitamin B12, 25-OH-D3, TSH, and serum zinc – this is a panel worth performing once a year on a plant-based diet. If you have deficiencies, check again after 3–4 months of supplementation to see if the doses are appropriate.

Many laboratories in Poland offer testing packages for vegans for 150–200 PLN. It is also worth remembering that reference standards for vitamin D in Poland vary depending on the laboratory – the optimal level of 25-OH-D3 is 40–60 ng/ml (100–150 nmol/l), and not just "above 20 ng/ml", which is the lower limit of many standards. At a level of 20–30 ng/ml, the real risk of deficiency and its consequences (osteoporosis, reduced immunity, worse mood) is increased.

Remember that test results are a starting point, not a verdict. Most deficiencies in vegans can be corrected within 3–6 months of appropriate supplementation and minor dietary modifications. A well-planned vegan diet is safe long-term – but "safe" does not mean "without any supplementation". A comparison of supplements for vegans with supplements for people over 40, where the supplementation priority is different, can be found in the article Suplementy dla kobiet po 40.

Frequently Asked Questions

Do vegans need to supplement vitamin B12?

Yes – without exception. Vitamin B12 is not found in any plant product in amounts sufficient to meet the demand. Pawlak et al. (Nutrition Reviews, 2013) showed a deficiency in 52% of vegans. Deficiency leads to irreversible damage to the nervous system. Dose: 50–100 µg/d or 1000 µg 2× a week.

Where can vegans get DHA from if they don't eat fish?

From marine algae oil (Schizochytrium, Nannochloropsis). Fish derive DHA from algae. The conversion of ALA from flax and hemp to DHA is less than 5–10% and does not meet the brain's demand. Dose: 250–500 mg DHA/d from vegan algae capsules.

Do vegetarians need to supplement iron?

Not everyone, but the risk is higher. Non-heme iron from plants is absorbed 5–15 times worse than heme iron from meat. Test ferritin once a year. With ferritin below 30 µg/l, supplementation is indicated. Vitamin C taken with a meal improves the absorption of non-heme iron.

How much vitamin D should a vegan take?

In the winter season (October–March) 2000–4000 IU of D3 daily. Vegans look for D3 from lichens (not from sheep lanolin) or D2. EFSA considers 4000 IU/d to be safe for adults. It is best to combine with K2 MK-7 (vegan).

Can hemp support a vegan diet?

Yes – especially hulled hemp seeds as a source of complete protein (31 g/100 g), ALA omega-3, and zinc. However, ALA does not replace DHA from algae for brain function – you need both. Hemp oil is a good addition to a daily plant-based diet.

Jaki cynk dla wegan?

Zinc from plants is poorly absorbed due to phytic acid. Soaking and sprouting legumes increases zinc availability. When supplementing, choose zinc citrate or picolinate (10–15 mg/d). Do not exceed 40 mg/d. Do not combine with iron or coffee.

This article is for informational and educational purposes and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.

Author: Michał Waluk · Published: 2026-05-04 · Updated: 2026-05-04