Vegan Nutrition Science

Key nutrients

Nutrients that need attention on a vegan diet

Vitamin B12 — the essential supplement

Vitamin B12 is produced by microorganisms and is found reliably only in animal products and fortified foods. B12 deficiency is the only genuine nutritional risk that vegans consistently face without supplementation — and it can cause irreversible neurological damage if left untreated.

• Recommendation: Take a B12 supplement — 2,000 mcg cyanocobalamin once weekly, or 25–100 mcg daily. Both are effective.
• Fortified plant milks, nutritional yeast, and some breakfast cereals contain B12, but amounts are often insufficient as a sole source.
• Blood levels decline slowly — deficiency symptoms may not appear for years after dietary sources are eliminated, which is why many vegans feel fine without supplementing initially.

Protein

Plant proteins are often described as "incomplete" because individual sources may be low in one or more essential amino acids. In practice, this is easy to address:

• Eat varied protein sources throughout the day — legumes (beans, lentils, chickpeas), tofu, tempeh, edamame, seitan, and whole grains all contribute.
• Soy protein (tofu, tempeh, edamame) is a complete protein with a quality score equivalent to meat.
• Slightly higher total protein intake (1.0–1.2g/kg vs. 0.8g/kg for omnivores) is often recommended to account for lower digestibility of some plant proteins.
• Legumes at every meal is a practical shortcut: lentils (18g protein/cup), chickpeas (15g), black beans (15g), firm tofu (20g/cup).

Omega-3 fatty acids

EPA and DHA — the long-chain omega-3s important for brain and heart health — are found mainly in oily fish and algae. ALA (from flaxseed, walnuts, chia seeds) converts to EPA/DHA in the body, but conversion rates are low (typically 5–10% for EPA, less for DHA).

• Recommendation: Take an algae-based EPA/DHA supplement (250–500 mg/day). Algae is where fish get their omega-3s — the algae supplement skips the middlefish.
• Also eat ALA-rich foods daily: ground flaxseed, walnuts, chia seeds, hemp seeds.

Iron

Plant foods contain non-heme iron, which is absorbed less efficiently than heme iron from meat. However, vegan diets are typically high in iron — the issue is bioavailability.

• Good sources: Legumes, tofu, tempeh, fortified cereals, pumpkin seeds, cashews, dark leafy greens.
• Pair iron-rich foods with vitamin C to dramatically increase absorption (e.g., lemon juice on lentils, peppers with beans).
• Avoid coffee/tea with iron-rich meals — tannins reduce absorption.
• Studies show most long-term vegans are not iron deficient, though women and athletes should monitor levels.

Calcium

Dairy is the most common calcium source in omnivore diets — but many plant foods are excellent calcium sources when consumed in adequate quantities.

• Good sources: Fortified plant milks (choose ones with 120mg+ calcium per 100ml), calcium-set tofu, kale, bok choy, broccoli, fortified orange juice, tahini.
• Target 1,000 mg/day (1,200 mg for over 50s). A glass of fortified soy milk + calcium-set tofu + leafy greens reaches this easily.
• Vegans who avoid fortified foods and greens are at higher fracture risk — studies showing slightly higher fracture rates in vegans are largely explained by inadequate calcium intake.

Vitamin D

Vitamin D deficiency is common across all dietary patterns in northern latitudes — not a vegan-specific issue. Most people benefit from supplementation, especially in winter.

• Recommendation: 1,000–2,000 IU vitamin D3 daily (vegan D3 from lichen is available) or D2. Sun exposure (10–30 minutes, skin exposed) when available.
• Fortified plant milks and some mushrooms contain D, but rarely enough as sole sources.

Iodine

Iodine in vegan diets is often overlooked. Dairy is iodized in many countries via cow feed and equipment cleaning products — plant milks typically don't replicate this.

• Options: Use iodized salt; eat seaweed occasionally (nori is lower in iodine, kelp is higher — but kelp can provide too much); take a supplement providing 150 mcg/day.

Zinc

Zinc absorption from plants is lower due to phytates. Vegans tend to have slightly lower zinc levels but rarely deficiency-level values.

• Good sources: Legumes, tofu, tempeh, nuts, seeds, whole grains.
• Soaking and sprouting legumes and seeds reduces phytate content and improves absorption.

Practical guide

A simple supplement protocol

Most vegans need only a few supplements to cover all nutritional bases: