What vitamins do vegans tend to lack? A comprehensive guide

October 29, 2025 •

5 min read

According to a systematic review published in 2021, vegans generally have significantly lower intakes and blood levels of vitamin B12, vitamin D, and iodine compared to meat-eaters. Understanding what vitamins do vegans tend to lack is crucial for maintaining optimal health and preventing long-term deficiencies on a plant-based diet. A well-planned vegan diet is healthy, but awareness and proactive measures are key to addressing potential nutritional shortfalls.

Quick Summary

A vegan diet can be deficient in key nutrients found primarily in animal products, including vitamin B12, vitamin D, and specific minerals. Strategic meal planning, consumption of fortified foods, and appropriate supplementation are essential to prevent and manage potential deficiencies for those on a plant-based diet.

Key Points

Vitamin B12 is essential for vegans: This vitamin is not naturally present in plant foods, making supplementation via tablets or fortified foods mandatory for nervous system health and red blood cell production.
Monitor Vitamin D levels: Vegans, like many non-vegans, can be low in vitamin D, particularly in colder climates with less sunlight. Supplementation and fortified foods are key for bone health and immunity.
Increase iron absorption with Vitamin C: While plant foods like lentils and greens are good iron sources, the iron (non-heme) is less bioavailable. Pairing these with Vitamin C-rich foods significantly boosts absorption.
Consider an algal oil supplement for Omega-3s: Conversion of plant-based ALA to the active omega-3s EPA and DHA is inefficient. Algae-based supplements are the most reliable vegan source for brain and heart health.
Ensure adequate zinc and iodine intake: Phytates in plant foods can hinder zinc absorption, while iodine content varies in plants based on soil. Use iodized salt or consider supplements for these crucial minerals.
Plan your diet strategically: A diverse diet rich in whole plant foods, including fortified options, is essential to cover a wider range of nutrients. Relying solely on unprocessed plant foods may not be enough.
Supplementation is a proactive measure, not a failure: Taking targeted supplements to address potential gaps is a smart strategy to ensure optimal health on a plant-based diet, just as it can be for omnivores.

Essential Vitamins and Nutrients to Monitor on a Vegan Diet

Transitioning to a vegan diet offers numerous health and environmental benefits, but it also removes common sources of certain vitamins and minerals. The key to a healthy plant-based lifestyle is careful planning and awareness of these potential gaps. The following are the most common nutrients that vegans need to monitor and actively manage.

Vitamin B12

Vitamin B12 is arguably the most critical vitamin for vegans to monitor. It is produced by bacteria and is found almost exclusively in animal products, with no reliable, naturally occurring plant-based sources.

Why it's important: Vitamin B12 is essential for healthy nerve function, red blood cell formation, and DNA synthesis. A deficiency can lead to severe and irreversible nerve damage, megaloblastic anemia, and fatigue.
Vegan sources: Since B12 does not come from plants, vegans must get it from reliable sources. These include:
- Fortified foods: Plant-based milks, cereals, and nutritional yeast are often fortified with B12.
- Supplements: A daily or weekly B12 supplement is the most reliable method. Dosages can vary, so it's best to consult a healthcare provider.

Vitamin D

Often called the 'sunshine vitamin,' vitamin D plays a crucial role in the body, yet dietary intake is often limited for vegans and omnivores alike.

Why it's important: Vitamin D helps the body absorb calcium, supporting bone health and immune function. Deficiency can increase the risk of conditions like osteoporosis.
Vegan sources: While sunlight is a primary source, dietary options for vegans include:
- Fortified foods: Some plant-based milks, orange juices, and cereals are fortified with vitamin D.
- UV-exposed mushrooms: Some mushrooms that have been exposed to ultraviolet light can be a source of vitamin D2.
- Supplements: Many vegans, especially those with limited sun exposure, benefit from a vitamin D supplement. Vegan D3 derived from lichen is available and often more effective than D2.

Iodine

Iodine is a mineral vital for thyroid function and metabolic regulation, and its availability in plant foods depends heavily on the mineral content of the soil.

Why it's important: The thyroid gland uses iodine to produce hormones that regulate metabolism and support brain development, especially important during pregnancy and infancy. Deficiency can cause an enlarged thyroid (goitre), fatigue, and weight gain.
Vegan sources: To ensure adequate intake, vegans can use:
- Iodized salt: A half-teaspoon of iodized salt can meet daily needs.
- Seaweed: Seaweed varieties like nori are rich sources, though iodine levels can be inconsistent.
- Supplements: An iodine supplement can provide consistent intake.

Iron

Iron is necessary for producing red blood cells and transporting oxygen throughout the body. While vegans often consume sufficient iron from plant foods, absorption can be a challenge.

Why it's important: Iron deficiency can lead to anemia, causing fatigue, weakness, and impaired cognitive function.
Challenges with absorption: Plant-based (non-heme) iron is less bioavailable than animal-based (heme) iron. Phytates in whole grains and legumes can also inhibit absorption.
Boosting iron intake: Vegans can improve absorption by:
- Pairing with Vitamin C: Consuming iron-rich foods with a vitamin C source (e.g., bell peppers, citrus) significantly increases absorption.
- Food sources: Lentils, beans, tofu, fortified cereals, and dark leafy greens are excellent sources.

Comparison of Key Nutrient Sources


Nutrient	Primary Animal Source	Vegan Source (with higher iron absorption)	Absorption Challenges for Vegans	Supplementation Recommendation
Vitamin B12	Meat, dairy, eggs	Fortified foods, nutritional yeast	Not naturally present in most plant foods	Essential, daily or weekly
Vitamin D	Fatty fish, eggs, dairy	Fortified milks/cereals, UV mushrooms	Limited sun exposure, less effective D2 conversion	Often recommended, especially in winter
Iron	Red meat (heme iron)	Lentils + Vitamin C source	Non-heme iron is less bioavailable; inhibited by phytates	Only if blood tests show deficiency
Calcium	Dairy products	Kale, fortified milks, calcium-set tofu	Oxalates and phytates can reduce bioavailability	Important if dietary intake is consistently low
Omega-3s (DHA/EPA)	Fatty fish, fish oil	Algal oil supplements	Inefficient conversion from plant-based ALA	Often recommended for optimal levels
Zinc	Meat, dairy, seafood	Legumes, nuts, seeds, tofu	Phytates can reduce absorption	Can be beneficial if dietary intake is low
Iodine	Dairy, seafood	Iodized salt, seaweed	Inconsistent levels in plant foods	Can be beneficial if not using iodized salt

Zinc and Omega-3 Fatty Acids

Beyond the vitamins, zinc and long-chain omega-3 fatty acids are two other nutrients that require attention in a vegan diet.

Zinc

Zinc is vital for immune function, metabolism, and cell repair. While found in many plant foods, its absorption is often hindered.

Why it's important: A deficiency can lead to immune system issues, hair loss, and poor wound healing.
Improving absorption: Soaking and sprouting legumes, nuts, and seeds can reduce phytate levels and increase zinc bioavailability.
Vegan sources: Whole grains, tofu, tempeh, legumes, nuts, and seeds are good sources.

Omega-3s (EPA & DHA)

Long-chain omega-3 fatty acids EPA and DHA are crucial for brain and heart health. While the body can convert the plant-based omega-3 ALA into EPA and DHA, this conversion is highly inefficient.

Why they're important: Adequate levels are important for cognitive function and reducing inflammation. Low levels have been observed in vegans.
Vegan sources: The most effective and direct vegan source of EPA and DHA is algae-based oil supplements. Plant sources like flaxseeds, walnuts, and chia seeds provide ALA, which the body can convert, but it is not a sufficient source of EPA and DHA for many individuals.

Conclusion

While a vegan diet can be immensely beneficial, it requires a conscious effort to obtain a complete spectrum of nutrients typically found in animal products. The main vitamins and minerals that vegans tend to lack or absorb less efficiently are vitamin B12, vitamin D, iodine, iron, calcium, zinc, and long-chain omega-3s. By incorporating fortified foods, choosing whole-food plant sources wisely, and using targeted supplementation, individuals can effectively manage their nutritional needs. Consulting with a healthcare provider or a registered dietitian is a great way to create a personalized nutrition plan and monitor nutrient levels to ensure a healthy and sustainable vegan lifestyle. For more information, visit the National Institutes of Health.

Frequently Asked Questions

Yes, unless actively managed, a vegan diet is almost certain to be low in vitamin B12 because this nutrient is found almost exclusively in animal products. Reliable sources include fortified foods and B12 supplements, which are essential for nerve and blood health.

Many vegans need a vitamin D supplement, especially those with limited sun exposure. While some fortified foods contain D2, D3 from animal sources is more efficient. Vegan D3 supplements from lichen are available to ensure adequate levels for bone health.

To improve iron absorption, vegans should pair iron-rich plant foods like lentils and leafy greens with a source of vitamin C. Avoiding tea and coffee around mealtimes, which can inhibit iron absorption, also helps.

The most effective vegan source for DHA and EPA is an algae-based oil supplement. While plant sources like flaxseeds contain ALA, the body's conversion to DHA and EPA is too inefficient for most people to rely on.

Yes, vegans can get enough calcium from sources like calcium-set tofu, fortified plant milks, and low-oxalate greens such as kale and broccoli. Strategic food choices can meet daily requirements without consuming dairy products.

Zinc is a concern because plant sources contain phytates, which can bind to zinc and reduce its absorption. Vegans should aim for higher overall zinc intake and use techniques like soaking grains and legumes to reduce phytate levels.

Reliable vegan sources of iodine include iodized table salt and seaweed. Because the iodine content of produce is inconsistent, these controlled sources or a supplement are important to ensure proper thyroid function.

While a whole-foods vegan diet is healthy, targeted supplementation for nutrients like B12 is often necessary. Supplements for vitamin D, iodine, and omega-3s are commonly recommended to cover potential gaps that even careful planning may miss.

Symptoms of deficiencies can include fatigue, tingling sensations, or low mood. The best way to know for sure is to consult a healthcare provider for a blood test. They can help create a tailored plan for dietary changes or supplementation.