Understanding Vegan Nutrition: What Deficiency is More Common in Vegans?

October 7, 2025 •

4 min read

According to scientific literature, vegans, especially those who do not supplement, are at a significantly higher risk for certain nutritional deficiencies. The most critical gap is with vitamin B12, a deficiency that is more common in vegans due to its limited presence in plant-based foods. However, several other nutrients also require careful management to ensure a balanced and healthy plant-based diet.

Quick Summary

Adhering to a vegan diet necessitates careful nutritional planning to avoid deficiencies. This article examines key nutrient gaps frequently associated with veganism, detailing the causes, symptoms, and effective strategies for prevention, including fortification, targeted food choices, and supplementation.

Key Points

Vitamin B12 is non-negotiable: Due to its near-exclusive presence in animal products, all vegans must take a reliable B12 supplement to prevent severe neurological damage and anemia.
Optimize iron absorption: The iron from plant foods is less bioavailable, so pair iron-rich foods with vitamin C sources to enhance uptake and avoid inhibitors like coffee and tea.
Prioritize fortified foods for calcium: Since some plant calcium is less absorbable, rely on calcium-fortified plant milks, yogurts, and calcium-set tofu to meet daily requirements.
Supplement with vitamin D, especially in winter: Most food sources of vitamin D are animal-based, making supplementation important, particularly for those with limited sun exposure.
Consider zinc and omega-3 supplements: Lower bioavailability of plant-based zinc and inefficient conversion of plant-based omega-3s mean supplementation may be necessary to ensure adequate intake.
Regular monitoring is vital: Annual check-ups with a healthcare provider can help assess nutrient levels and ensure a vegan diet remains nutritionally sound.

The Most Pressing Concern: Vitamin B12

Among the various nutrients that require attention on a vegan diet, vitamin B12 stands out as the most critical and universally recommended for supplementation. Vitamin B12 is essential for nerve function, DNA synthesis, and the formation of red blood cells. A deficiency can lead to severe health issues, including megaloblastic anemia and neurological damage that, if left untreated, can become irreversible.

The primary reason for this vulnerability is that vitamin B12 is produced by bacteria and is found almost exclusively in animal products. While some plant-based foods, such as nutritional yeast and certain fortified products like plant milks and cereals, contain added B12, relying solely on these sources can be unreliable. For this reason, all vegans are strongly advised to take a B12 supplement consistently to ensure adequate intake.

Addressing Other Key Nutrients

Beyond vitamin B12, a well-planned vegan diet must account for several other nutrients that are often more difficult to obtain or absorb from plant sources. These include iron, calcium, vitamin D, zinc, and specific omega-3 fatty acids.

Iron

While plant-based diets can provide ample iron, the non-heme iron found in plants is less bioavailable than the heme iron from meat. Vegans, particularly menstruating women and athletes, may have lower iron stores and a higher risk of deficiency.

To maximize absorption:

Pair iron-rich foods (legumes, leafy greens, fortified cereals) with a source of vitamin C (citrus fruits, bell peppers, broccoli).
Avoid drinking coffee or tea around mealtime, as the tannins can inhibit iron absorption.

Calcium and Vitamin D

Healthy bones require both calcium and vitamin D, and vegans must be proactive about their intake. Dairy products are a major source of calcium in omnivorous diets, and while many plant foods contain calcium, compounds like oxalates in some greens can reduce its absorption.

Calcium Sources: Opt for calcium-fortified plant milks, yogurts, and tofu set with calcium sulfate. Other good sources include kale, collard greens, almonds, and tahini.
Vitamin D Sources: The primary source of vitamin D is sun exposure, but dietary sources are limited for everyone. Natural vitamin D3 comes from animal products, though vegan D3 supplements derived from lichen are available. Fortified foods and supplements are often necessary, especially during winter months.

Zinc

Vegans often have lower zinc intake and status due to the presence of phytates in many plant foods, which bind to zinc and inhibit its absorption. Zinc is vital for immune function and overall health.

Sources: Good plant-based sources include legumes, nuts, seeds, and whole grains.
Strategies: Soaking, sprouting, or fermenting grains and legumes can help reduce phytate levels and increase zinc absorption. A daily supplement is also a reliable way to ensure adequate intake.

Omega-3 Fatty Acids

Omega-3s, specifically the long-chain fatty acids EPA and DHA, are crucial for brain and heart health. While plant sources like flaxseeds, walnuts, and chia seeds contain the omega-3 ALA, the body's conversion of ALA to EPA and DHA is inefficient.

Sources: An algae-based DHA supplement is a reliable vegan source of preformed EPA and DHA.
Improve Conversion: Reduce intake of linoleic acid (an omega-6) by moderating consumption of certain vegetable oils to optimize the body's conversion of ALA.

Comparison of Common Vegan Nutrient Sources


Nutrient	Primary Animal Source (Non-Vegan)	Common Vegan Source	Bioavailability/Absorption Considerations
Vitamin B12	Meat, dairy, eggs	Supplements, fortified nutritional yeast, plant milks	Only reliable source for consistent B12 is supplementation
Iron	Red meat, poultry	Legumes, leafy greens, seeds, fortified cereals	Non-heme iron is less absorbed; enhance with Vitamin C
Calcium	Dairy products	Fortified plant milks, calcium-set tofu, kale, almonds	Absorption can be inhibited by oxalates; fortified foods are key
Vitamin D	Fatty fish, eggs	Fortified foods, UV-treated mushrooms	Sun exposure is the main source; supplements often necessary
Zinc	Meat, shellfish	Legumes, nuts, seeds, whole grains	Absorption reduced by phytates; soaking and sprouting can help
Omega-3 (EPA/DHA)	Oily fish	Algae oil supplements	Inefficient conversion from plant-based ALA sources

The Critical Role of Supplementation

While a thoughtfully constructed vegan diet can meet most nutritional needs, supplementation plays a vital role in preventing deficiencies for key nutrients. Vitamin B12 supplementation is non-negotiable for all vegans. Depending on individual sun exposure, location, and fortified food intake, a vitamin D supplement is also often recommended. Additionally, an algae-based omega-3 supplement can ensure adequate intake of EPA and DHA.

For iron and zinc, careful dietary planning can often suffice, but monitoring your intake and considering supplementation may be necessary if blood tests indicate low levels. A yearly check-up with a doctor or registered dietitian can help identify and address any potential gaps.

Conclusion

While a vegan diet offers numerous health and environmental benefits, it requires diligence to avoid specific nutrient deficiencies that are more common in vegans. The most notable is vitamin B12, for which supplementation is essential. Other key nutrients, including iron, calcium, vitamin D, zinc, and omega-3s, must also be strategically managed through a varied diet of whole foods, fortified products, and, in some cases, supplements. With proper planning and awareness, a vegan diet can be perfectly healthy and nutritionally adequate throughout all stages of life. For further information and expert advice on optimizing a plant-based diet, consult reputable health resources like The Vegan Society.

Note: This is not medical advice. Consult with a healthcare professional or registered dietitian for personalized dietary recommendations.

Frequently Asked Questions

Vitamin B12 is the most crucial supplement for vegans. It is not reliably available in plant-based foods, and a deficiency can lead to severe health consequences like neurological damage.

The iron in plant-based foods (non-heme iron) is not as easily absorbed by the body as the iron from meat (heme iron). Additionally, compounds called phytates in grains and legumes can further inhibit absorption.

Vegans can get enough calcium by consuming fortified plant milks, yogurts, and calcium-set tofu. Certain leafy greens like kale and broccoli are also good sources, but the calcium in spinach is less absorbable.

The most reliable vegan source of the beneficial long-chain omega-3s (EPA and DHA) is an algae-based oil supplement. Plant sources like flaxseeds and walnuts contain ALA, which the body converts inefficiently.

Many vegans have lower zinc levels due to lower dietary intake and absorption issues from plant-based foods. Supplementation is often recommended, especially for those who consume high amounts of whole grains and legumes.

Yes, vitamin D deficiency can be a concern, as few foods naturally contain it, and sunlight is the primary source. Vegan supplements derived from lichen and fortified foods are important, especially in regions with less sunlight.

Ignoring these deficiencies can lead to serious health problems. For example, B12 deficiency can cause neurological damage, iron deficiency can cause anemia and fatigue, and inadequate calcium and vitamin D can lead to bone conditions like osteoporosis.