Which is the most common vitamin deficiency for vegans?

November 15, 2025 •

4 min read

Studies have shown that over half of vegans who do not take supplements may be deficient in B12, making it the most common vitamin deficiency for vegans. This essential nutrient is primarily found in animal products, so those following a strictly plant-based diet must take proactive steps to ensure an adequate intake.

Quick Summary

Vitamin B12 is the most prevalent nutrient shortfall among those on a vegan diet, as it is found almost exclusively in animal-based foods. Proper planning, including supplements and fortified foods, is crucial to prevent deficiency and its associated health risks.

Key Points

Vitamin B12 is the primary concern: Due to its absence in unfortified plant foods, vitamin B12 deficiency is the most common nutritional shortfall for vegans.
Supplements are essential for B12: The most reliable and recommended way for vegans to get B12 is through supplements or consistently using fortified foods.
Vitamin B12 stores can be deceptive: The body can store B12 for several years, so deficiency symptoms may not appear immediately, requiring proactive action.
Other nutrients also need attention: Other potential deficiencies include Vitamin D, iodine, iron, calcium, and Omega-3 fatty acids.
Planning and fortification are key: A well-planned vegan diet that includes fortified plant milks, cereals, and nutritional yeast can help prevent many deficiencies.
Combine foods for better absorption: To increase iron absorption, pair iron-rich plant foods with a source of vitamin C.
Professional guidance is important: Consulting a healthcare provider or dietitian is especially crucial for vulnerable groups like pregnant women, older adults, or those with underlying health conditions.

Vitamin B12 is the most common vitamin deficiency for vegans, and it is a critical concern that requires careful attention. This water-soluble vitamin plays a crucial role in nerve function, DNA synthesis, and red blood cell formation, and a deficiency can lead to serious neurological and hematological issues. The reason for this high prevalence is simple: B12 is produced by microorganisms and accumulates in animal tissues, meaning it is not reliably present in plant-based foods unless fortified.

Understanding the B12 Deficiency Risk

For those new to a vegan diet, the risk of B12 deficiency may not be immediately apparent. This is because the human body can store B12 in the liver for several years, which can mask an insufficient dietary intake for a long time. However, once these reserves are depleted, symptoms can manifest gradually, making it difficult to pinpoint the cause. This delayed onset makes consistent supplementation or consumption of fortified foods essential from the very beginning of a vegan diet. Research indicates that deficiency rates among vegans who do not supplement are significantly higher than in omnivores.

Other Common Nutrient Concerns for Vegans

While B12 is the most critical vitamin deficiency, other nutrients also require attention in a vegan diet. These include Vitamin D, which is essential for calcium absorption and bone health, and iodine, a mineral important for thyroid function. Plant-based sources of these nutrients exist, but their bioavailability or concentration can be lower than in animal products. For instance, non-heme iron from plant sources is not as easily absorbed as heme iron found in meat, and the calcium in some leafy greens is bound by oxalates, reducing its availability. Careful meal planning and potentially supplements are needed to address these potential shortfalls.

Comparison of Common Vegan Nutrient Sources


Nutrient	Primary Function	Vegan Food Sources	Key Considerations
Vitamin B12	Nerve function, red blood cell formation	Fortified cereals, nutritional yeast, supplements	Supplementation is essential; natural plant sources are unreliable.
Vitamin D	Calcium absorption, bone health	Fortified plant milks, UV-treated mushrooms, sunlight	Sun exposure is variable; many vegans require a supplement.
Iodine	Thyroid hormone production	Iodized salt, seaweed, fortified plant milks	Seaweed can have excessive iodine; fortified products vary.
Iron	Oxygen transport in blood	Legumes, leafy greens, fortified cereals	Non-heme iron is less bioavailable; combine with Vitamin C for better absorption.
Calcium	Bone health, muscle function	Tofu (calcium-set), fortified plant milks, kale	Bioavailability varies; choose low-oxalate greens and fortified foods.
Omega-3s (DHA/EPA)	Brain and heart health	Algae oil supplements, flaxseeds, chia seeds	Conversion of ALA to DHA/EPA is inefficient; algae oil is a direct source.

Strategies for Preventing Nutrient Deficiencies

The key to a nutritionally sound vegan diet is mindful planning and reliable supplementation. For vitamin B12, this means consistently consuming fortified foods or taking a daily or weekly supplement. For other nutrients, a varied diet is crucial. For example, incorporating iodized salt into cooking and eating low-oxalate calcium sources like kale can help. To maximize iron absorption, pair iron-rich foods like lentils with a vitamin C source, such as citrus fruits or bell peppers. Given the variables of sun exposure and food fortification, many nutrition experts recommend that vegans also take a vitamin D supplement, especially during the darker months.

The Importance of Professional Guidance

While this information provides a solid starting point, personalized advice from a healthcare professional or registered dietitian is invaluable. They can help create a tailored plan that considers individual health status, age, and lifestyle. This is particularly important for at-risk groups like pregnant or breastfeeding women, older adults, and children. Regular blood tests can also help monitor nutrient levels and ensure that your dietary choices are supporting optimal health.

Conclusion

The most common vitamin deficiency for vegans is undoubtedly Vitamin B12, a non-negotiable nutrient that requires regular and reliable supplementation. While other deficiencies in nutrients like Vitamin D, iodine, iron, and calcium are also possible, they can often be managed through diligent meal planning that includes a wide variety of whole foods and fortified products. By acknowledging the specific nutritional challenges of a plant-based diet and actively addressing them, vegans can enjoy the health and ethical benefits of their lifestyle without compromising their nutritional well-being.

Note: For those considering a vegan diet, consulting with a medical professional or dietitian is highly recommended to ensure all nutritional needs are met. For further reading, an excellent resource on plant-based nutrition can be found at The Vegan Society's website, which offers extensive information on Vitamin B12 and other nutrients.(https://www.vegansociety.com/resources/nutrition-and-health/nutrients/vitamin-b12)

Frequently Asked Questions

B12 is almost exclusively found naturally in animal-based foods like meat, eggs, and dairy products because it is produced by microorganisms in animal guts. Since vegan diets exclude all animal products, they lack natural sources of this essential vitamin.

While fortified foods like nutritional yeast, plant-based milks, and cereals can provide some B12, relying solely on them may not be sufficient or consistent enough for all individuals. Supplements offer a more reliable way to meet your daily B12 requirements.

Symptoms can develop slowly and include fatigue, weakness, and neurological issues such as tingling in the hands and feet, memory problems, and difficulty with balance. A severe deficiency can lead to megaloblastic anemia.

In addition to B12, vegans should pay attention to Vitamin D, iodine, iron, calcium, and omega-3 fatty acids (specifically DHA and EPA). These can be obtained through careful planning, fortified foods, and supplements.

To enhance iron absorption from non-heme plant sources, consume them alongside foods rich in Vitamin C, such as citrus fruits, bell peppers, and broccoli. It is also recommended to avoid drinking coffee or tea with iron-rich meals, as they can inhibit absorption.

While some Vitamin D is produced by sun exposure, many factors can limit its effectiveness, and natural food sources for vegans are limited. Most health professionals recommend a supplement for vegans, especially during autumn and winter.

Iodine can be a concern for vegans, particularly if they do not consume iodized salt or iodine-fortified plant milks. Sources include iodized salt and seaweed, but excessive seaweed intake should be avoided to prevent over-consumption.