What health problems do vegans have? A Look at Nutrient Deficiencies

December 19, 2025 •

5 min read

A 2021 review found that vegans often have lower levels of key nutrients like vitamin B12, vitamin D, iron, and calcium compared to meat-eaters, which can lead to various health issues. Understanding what health problems do vegans have is crucial for anyone following or considering a plant-based diet to ensure it is nutritionally sound.

Quick Summary

Excluding animal products can increase a vegan's risk for deficiencies in vitamin B12, D, calcium, iron, and iodine. Careful meal planning, fortification, and supplementation are essential to prevent health complications such as anemia, neurological issues, and poor bone mineral density.

Key Points

Vitamin B12 is essential: As it is only found naturally in animal products, vegans must supplement or eat fortified foods regularly to prevent neurological damage and anemia.
Iron absorption is less efficient: Plant-based non-heme iron is harder for the body to absorb. Pairing it with vitamin C can significantly improve this, while avoiding coffee and tea at mealtimes can prevent inhibition.
Bone health requires attention: Vegans often have lower calcium and vitamin D intake, and absorption can be hindered by plant compounds, potentially leading to lower bone mineral density.
Omega-3 conversion is limited: The body poorly converts plant-based ALA into essential EPA and DHA, so an algae-based omega-3 supplement is often recommended for vegans.
Vulnerable groups need extra care: Pregnant women, children, and older adults have increased nutritional needs, making consistent monitoring and supplementation on a vegan diet particularly important.
Strategic planning is crucial: A healthy vegan diet is not automatic. It requires careful planning to include a variety of plant foods, fortified products, and supplements to prevent nutrient deficiencies.

Common Nutritional Deficiencies in a Vegan Diet

While a well-planned vegan diet can be very healthy, certain nutrients are primarily or exclusively found in animal products, making supplementation or fortification necessary. A lack of these nutrients can lead to specific health issues if not addressed proactively.

Vitamin B12 Deficiency

Vitamin B12 is essential for nerve function, DNA synthesis, and red blood cell production. Since it is synthesized by microorganisms and found in animal products, vegans must rely on fortified foods or supplements to avoid deficiency. Symptoms of a deficiency can include:

Extreme fatigue and lethargy
Numbness or tingling sensations, known as paresthesia
Memory loss and cognitive difficulties
Megaloblastic anemia
Neurological damage, which can be irreversible if untreated

Iron Deficiency and Anemia

Iron is vital for transporting oxygen in the blood via hemoglobin. Plant-based sources contain non-heme iron, which is less bioavailable than the heme iron found in meat. Although vegan diets often contain a high amount of non-heme iron, lower absorption can lead to deficiencies. Symptoms include fatigue, weakness, pale skin, and hair loss. Vegans can boost absorption by:

Pairing iron-rich foods like lentils, beans, and leafy greens with vitamin C sources (e.g., bell peppers, citrus fruits).
Avoiding tea and coffee around mealtimes, as they inhibit iron absorption.
Using cast iron cookware, which can increase iron content in foods.

Calcium and Bone Health Concerns

Calcium is crucial for maintaining bone density and strength. Dairy products are a major source in omnivorous diets, but vegans must rely on plant-based alternatives. Certain plant compounds, like oxalates in spinach and phytates in grains and legumes, can inhibit calcium absorption. Research suggests vegans may have lower bone mineral density, potentially increasing fracture risk. Good vegan calcium sources with high bioavailability include fortified plant milks, calcium-set tofu, kale, and collard greens.

Vitamin D Insufficiency

Vitamin D is necessary for calcium absorption and bone health. While sunlight is the primary source, dietary intake is also important. Since natural food sources are mostly animal-based, vegans are at higher risk of insufficiency. Symptoms can include bone pain, fatigue, and muscle weakness. Sources for vegans include fortified plant milks, UV-exposed mushrooms, and supplements.

Omega-3 Fatty Acids (EPA and DHA)

Omega-3s are crucial for heart and brain health. Plant foods contain ALA, which the body converts to the more usable EPA and DHA, but this conversion rate is low. Vegans can obtain ALA from walnuts, flaxseeds, and chia seeds. For direct EPA and DHA intake, algae-based supplements are the most effective option.

Iodine and Zinc

Iodine is needed for thyroid function, while zinc supports immune function and cell growth. Both can be lacking in a poorly planned vegan diet. Sources for iodine include iodized salt and seaweed, while zinc can be found in legumes, nuts, and whole grains.

Health Risks for Vulnerable Populations

Certain life stages and conditions require special attention to nutrient intake, making a poorly planned vegan diet particularly risky. These include:

Children and Adolescents: Their rapid growth and development require high nutrient density. Deficiencies in vitamins B12, D, and calcium can affect growth and bone mineralization.
Pregnant and Breastfeeding Women: Nutrient needs increase significantly during this period. Inadequate intake of B12, iodine, and iron can impact fetal development and the mother's health.
Older Adults: Absorption of certain nutrients, like B12, decreases with age, and the risk of osteoporosis increases, making careful dietary planning even more critical.

Navigating Veganism for Optimal Health

While potential issues exist, a vegan diet can be nutritionally adequate and beneficial with the right approach. Key strategies involve:

Consistent Supplementation: Take a reliable vitamin B12 supplement regularly. Consider supplements for vitamin D, iodine, and algae-based DHA/EPA, especially during winter or if dietary intake is uncertain.
Prioritizing Fortified Foods: Incorporate products like fortified plant milks, cereals, and nutritional yeast into your daily meals.
Diversifying Protein Sources: To ensure you get all essential amino acids, consume a wide variety of protein sources throughout the day, such as soy products, legumes, nuts, and whole grains.
Optimizing Mineral Absorption: Pair iron-rich meals with vitamin C sources and avoid inhibitors like coffee and tea around meal times. Choose calcium sources with low oxalate content, like kale over spinach.

Nutrient Bioavailability: Plant-Based vs. Animal-Based

To better understand the absorption differences, here is a comparison of key nutrients from plant and animal sources:


Nutrient	Animal-Based Sources	Plant-Based Sources	Bioavailability/Absorption Difference
Iron	Heme iron from meat and fish is easily absorbed.	Non-heme iron from plants (legumes, spinach) is less bioavailable.	Non-heme iron absorption is inhibited by phytates and tannins, but enhanced by vitamin C.
Calcium	Found in high amounts in dairy, with high bioavailability.	Available in leafy greens, fortified milks, and tofu, but absorption can be inhibited by oxalates and phytates.	The amount of calcium your body absorbs varies by plant source, e.g., kale's is high, spinach's is low.
Vitamin D	Primarily found in fatty fish, egg yolks, and fortified dairy.	Limited natural sources (some mushrooms), primarily relies on sun or fortification.	Vegan sources of vitamin D3 (from lichen) or D2 (from mushrooms/fortification) are needed when sun exposure is low.
Omega-3s	Long-chain EPA and DHA abundant in oily fish.	Plant sources provide ALA (walnuts, flaxseed), which has a low conversion rate to EPA and DHA.	Direct EPA and DHA supplementation via algae oil is needed for optimal intake.
Protein	Considered 'complete' with all essential amino acids.	Must be consumed from a variety of sources throughout the day to get all essential amino acids.	Plant proteins are generally less digestible than animal proteins.

Conclusion

For those on a vegan diet, acknowledging and addressing potential nutrient shortfalls is key to maintaining long-term health. While it is possible to obtain all necessary nutrients from plant-based sources, it requires mindful planning, incorporating fortified foods, and often using supplements, particularly for vitamin B12. As noted in a systematic review, while lifestyle factors play a role, specific nutrient deficiencies are a known risk that must be monitored. Consulting with a healthcare professional or a dietitian specializing in plant-based nutrition can provide tailored guidance and ensure your diet supports optimal wellness. NIH study on vegan diet impact

Frequently Asked Questions

The most common nutrient deficiencies for vegans include vitamin B12, vitamin D, calcium, iron, iodine, zinc, and long-chain omega-3 fatty acids (EPA and DHA).

Yes, a vegan diet can increase the risk of anemia, primarily due to lower levels of vitamin B12 and the less bioavailable form of non-heme iron found in plant foods. Proper supplementation and careful meal planning can prevent it.

Vegans often have lower intakes of calcium and vitamin D, and some plant compounds can hinder absorption, which can lead to lower bone mineral density over time. Fortified foods and supplements are key to managing this risk.

The most reliable way for vegans to get vitamin B12 is through regular supplementation. Fortified foods like plant milks, cereals, and nutritional yeast can also contribute, but supplements offer the most consistent dosage.

Yes, but it requires diligent planning and monitoring. Pregnant and breastfeeding women on a vegan diet must ensure adequate intake of critical nutrients like iron, iodine, and especially vitamin B12, often through supplements, to support both their health and fetal development.

To improve non-heme iron absorption, vegans should pair iron-rich foods like lentils and greens with vitamin C sources such as citrus fruits or bell peppers. Additionally, avoiding coffee and tea around meal times is helpful, as they inhibit iron absorption.

Not necessarily. Many processed vegan alternatives can be high in salt, sugar, and fat. While they can be a convenient source of protein, relying too heavily on them can lead to an imbalanced diet. Whole, unprocessed foods should form the basis of a healthy vegan diet.