What Vitamins Can't You Get From a Vegan Diet?

December 16, 2025 •

4 min read

According to a study published in the European Journal of Nutrition, vegans may consume similar levels of some micronutrients as non-vegans but often have notably lower levels of others. This highlights why it is critical for those following a plant-based diet to understand what vitamins can't you get from a vegan diet and how to supplement effectively.

Quick Summary

A vegan diet can be healthy but lacks certain vitamins naturally found in animal products, including B12, vitamin D, and key omega-3 fatty acids like DHA. Proper planning with fortified foods and supplements is essential for bridging these nutritional gaps and maintaining optimal health.

Key Points

Vitamin B12: This is the most crucial nutrient to supplement, as it is not naturally found in unfortified plant foods.
Vitamin D: While sunlight is a source, dietary options are limited on a vegan diet, and supplementation is often necessary, especially in winter.
Omega-3s (EPA & DHA): The conversion of plant-based ALA is inefficient, making microalgae-based supplements a recommended source for these long-chain fatty acids.
Iodine: Plant sources can be unreliable, so using iodized salt, eating seaweed, or taking a supplement is important for thyroid health.
Supplements are key: The most reliable and consistent way to obtain these essential nutrients is through supplementation or a consistent intake of fortified products.

A well-planned vegan diet can provide a wealth of health benefits, but it requires mindful attention to nutrients that are either absent or poorly absorbed from plant-based sources. Understanding what vitamins can't you get from a vegan diet is the first step towards ensuring complete nutrition through fortified foods or supplements.

Vitamin B12

Vitamin B12 is arguably the most critical nutrient for vegans to consider. It is primarily found in animal products, and no unfortified plant foods can provide a reliable source. B12 is essential for red blood cell formation, DNA synthesis, and neurological function. Deficiency can lead to anemia and irreversible nerve damage.

How to obtain B12 as a vegan

Since B12 is produced by microorganisms, not plants or animals, all humans get it from external sources. For vegans, this means relying on:

Fortified foods: Look for breakfast cereals, nutritional yeast, and plant milks (like soy or almond) that have been fortified with B12.
Supplements: The most reliable way for a vegan to get B12 is through a supplement. Options include a daily low-dose supplement or a high-dose supplement taken weekly.
Regular testing: It is recommended for vegans to have their B12 levels checked annually to monitor their status.

Vitamin D

Vitamin D, often called the "sunshine vitamin," is produced in the skin upon exposure to sunlight. While some can get enough from sun exposure, many factors, including geographic location, season, and skin tone, affect production. Dietary sources are also important, but many common sources, like oily fish, eggs, and dairy, are not vegan.

Vegan sources of Vitamin D

Sunlight: Aim for some safe sun exposure, especially during sunnier months. For those in northern latitudes or with darker skin, this can be insufficient.
UV-grown mushrooms: Certain mushrooms, like maitake and portobello, that have been exposed to UV light contain significant amounts of vitamin D2.
Fortified foods: Many plant-based products, such as cereals, plant milks, and spreads, are fortified with vitamin D.
Supplements: A vegan D3 supplement, often derived from lichen, is a reliable way to ensure adequate intake. Public health bodies in many countries recommend winter supplementation for everyone, not just vegans.

Long-Chain Omega-3 Fatty Acids (EPA and DHA)

While vegans can easily obtain alpha-linolenic acid (ALA), a short-chain omega-3 fatty acid, from seeds and nuts, the conversion of ALA to the longer-chain EPA and DHA is inefficient in the human body. EPA and DHA are crucial for brain health, eye function, and reducing inflammation. The primary dietary sources of EPA and DHA for most people are oily fish.

Vegan sources of EPA and DHA

Algae-based supplements: Fish get their omega-3s from consuming microalgae, so vegans can cut out the middleman and get EPA and DHA directly from microalgae supplements.
ALA-rich foods: Though conversion is poor, eating plenty of ALA-rich foods like flaxseed, chia seeds, and walnuts is still beneficial.

Iodine

Iodine is a vital mineral for thyroid function, and deficiencies can lead to metabolic issues. It is most commonly found in dairy and seafood. Plant-based sources of iodine can be unreliable as the concentration depends on the mineral content of the soil where the plants were grown.

How vegans can get enough iodine

Iodized salt: Using iodized table salt is a simple and effective way to meet iodine needs.
Seaweed: Nori, kelp, and wakame are excellent sources, though amounts can vary widely.
Fortified plant milks: Some plant milks are fortified with iodine, but it is not standard, so checking labels is necessary.
Supplements: An iodine supplement can ensure a consistent and adequate intake.

Comparison of Key Nutrients: Vegan vs. Omnivore


Nutrient	Primary Omnivore Sources	Primary Vegan Sources (often fortified)	Vegan Diet Supplementation Recommended?
Vitamin B12	Meat, dairy, eggs	Fortified cereals, nutritional yeast, plant milks	Yes, highly recommended
Vitamin D	Oily fish, eggs, dairy	Sun exposure, UV-grown mushrooms, fortified foods	Yes, especially in autumn and winter
Omega-3s (EPA/DHA)	Oily fish	Microalgae supplements	Yes, recommended to ensure adequate intake
Iodine	Seafood, dairy	Iodized salt, seaweed, fortified products	Yes, to ensure consistent and sufficient intake

Conclusion: Strategic nutrition for the plant-based lifestyle

While a whole-food, plant-based diet is packed with vitamins and antioxidants, the absence of animal products means a few key nutrients require careful attention. The answer to "what vitamins can't you get from a vegan diet?" lies primarily in B12, vitamin D, EPA/DHA, and iodine. Fortunately, these can all be obtained reliably through fortified foods and high-quality supplements. By understanding these nutritional considerations and proactively addressing them, vegans can ensure their diet remains balanced and supportive of long-term health.

Vegan Society's Guide to Vegan Nutrition

Frequently Asked Questions

Vitamin B12 is the most difficult to get on a vegan diet because it is not reliably found in any unfortified plant-based foods. Vegans must obtain B12 from fortified foods or, more reliably, from a supplement.

Sunlight exposure is a primary source of Vitamin D, but its effectiveness varies depending on season, location, and skin tone. During colder or darker months, relying on fortified foods or taking a vegan D3 supplement is advisable.

While flax and chia seeds contain the omega-3 ALA, the body's conversion of ALA into the more active forms, EPA and DHA, is very inefficient. An algae-based supplement is recommended to ensure adequate intake of EPA and DHA.

You can get iodine by using iodized salt in your cooking, eating seaweed like nori or kelp, and consuming some fortified plant-based dairy alternatives. Some vegans may still benefit from a supplement.

A prolonged lack of B12 can lead to serious health issues, including anemia, fatigue, weakness, and irreversible nervous system damage. It is a non-negotiable supplement for all vegans.

Vitamin K2, which is important for bone and cardiovascular health, is not abundant in most plant foods, though some fermented foods like natto contain it. Like other nutrients, vegans can opt for a supplement to ensure adequate intake.

Yes, with careful planning, it is possible. Good vegan sources of calcium include fortified plant milks and tofu, green leafy vegetables like kale, sesame seeds, and certain pulses.