Which vitamins are not found in plants?

December 31, 2025 •

4 min read

According to the National Institutes of Health, vitamin B12 is found in a wide variety of animal foods, but not naturally in plant foods. This is one of the key distinctions answering the question, which vitamins are not found in plants?, a critical consideration for anyone following a vegan or vegetarian diet.

Quick Summary

Certain vitamins are not naturally present in plants, with B12 being the most prominent example. Vitamin D is also not a reliable plant source, as it is produced in the skin from sunlight and found mainly in animal products. Fortified foods and supplements are necessary to meet the dietary needs for these vitamins on a plant-based diet.

Key Points

Vitamin B12 is the most notable vitamin absent from plants: It is produced by microorganisms, and is acquired by humans primarily through animal products or supplementation.
Vitamin D is not reliably found in plants: While the body produces it from sunlight, most dietary sources are animal-based or fortified products. UV-exposed mushrooms are a plant-kingdom exception.
Fortification and supplements are essential for vegans: Fortified cereals, plant milks, and nutritional yeast are common sources of B12 and D for those on a plant-based diet.
Bioavailability of nutrients differs between plant and animal sources: For example, iron from plant sources (nonheme) is less readily absorbed than heme iron from animal products, requiring compensatory strategies.
Other nutrients like Omega-3s and Iodine need consideration: The long-chain Omega-3s (EPA/DHA) are primarily from marine life, though algae supplements exist. Iodine levels depend on soil quality, making iodized salt a reliable source.
Deficiency symptoms for B12 can be severe: Symptoms like fatigue, weakness, and neurological issues can appear gradually due to the body's storage capacity, highlighting the need for consistent intake.

Most plant foods provide a rich and diverse source of essential vitamins and minerals, from Vitamin C in citrus fruits to Vitamin K in leafy greens. However, a few key vitamins are almost exclusively found in animal products or are synthesized differently, making them a concern for those on plant-based diets. Understanding these exceptions is crucial for maintaining optimal health without animal products.

Vitamin B12: The Primary Gap in Plant-Based Nutrition

Vitamin B12, also known as cobalamin, is the most notable vitamin that is not found in plants. This is because it is produced by specific bacteria and archaea, not by plants, animals, or fungi. Animals, especially ruminants like cattle, acquire vitamin B12 through a symbiotic relationship with bacteria in their digestive tracts. Humans then obtain it by consuming these animal products, including meat, eggs, and dairy.

For those on a strictly plant-based (vegan) diet, reliable sources of vitamin B12 are synthetic and must be obtained through supplementation or fortified foods. This is particularly important because the human body stores vitamin B12, and it can take several years for a deficiency to manifest. Symptoms of a vitamin B12 deficiency can be severe and include fatigue, weakness, nerve damage (tingling and numbness), and in extreme cases, megaloblastic anemia. While some plant-based foods like fermented tempeh or certain algae (nori, chlorella) have been found to contain B12, the amounts are highly variable and may contain inactive analogues that interfere with true B12 absorption. Therefore, they are not considered reliable sources.

The Importance of Consistent Intake

For vegans, ensuring a consistent intake of B12 is non-negotiable. Strategies include:

Regular Supplements: Taking a daily or weekly B12 supplement is the most reliable method.
Fortified Foods: Many cereals, plant-based milks, and nutritional yeasts are fortified with B12. Checking the nutrition label is key.
Monitoring Levels: Regular blood tests to check B12 status are recommended for long-term vegans.

Vitamin D: The Sunshine Vitamin with Animal Sources

Vitamin D is another nutrient that is not readily found in most common plant foods. The body produces Vitamin D (specifically D3) when the skin is exposed to sunlight. While this is the primary source for most people, dietary intake is still important. Few foods naturally contain vitamin D, and most of these are animal-based, such as fatty fish, egg yolks, and beef liver.

Vitamin D in Fungi

An exception exists within the fungi kingdom: mushrooms. Just like humans, mushrooms can produce Vitamin D when exposed to UV light. Store-bought mushrooms are often grown in the dark and have very low levels, but wild mushrooms or those explicitly treated with UV light contain significant amounts of Vitamin D2. For vegans, this offers a natural food-based source, though supplements and fortified foods remain more reliable and accessible.

Comparing Plant vs. Animal Sources for Key Vitamins


Nutrient	Primary Source (Animal)	Plant-Based Alternative	Key Difference
Vitamin B12	Meat, fish, eggs, dairy	Fortified foods (yeast, cereals), supplements	Synthetic vs. Natural: Plants do not produce B12; animal sources are naturally derived from microbial interaction.
Vitamin D	Fatty fish, egg yolks, beef liver	Fortified foods (plant milks), UV-exposed mushrooms	Source of D3 vs. D2: Animal sources contain D3, while plant sources (mushrooms) contain D2. Most fortified products are D2.
Iron	Heme iron in meat, poultry, fish	Nonheme iron in legumes, nuts, spinach	Bioavailability: Heme iron from animal sources is more easily absorbed by the body than nonheme iron from plants.
Calcium	Dairy products	Tofu, kale, fortified plant milks	Absorption Inhibitors: Some plant foods contain oxalates and phytates that can reduce calcium absorption.

Other Nutritional Considerations for Plant-Based Diets

While B12 and D are the main vitamins not reliably found in unfortified plant foods, other nutrients require attention on a vegan diet.

Omega-3 Fatty Acids

Alpha-linolenic acid (ALA), a plant-based omega-3, is found in flaxseeds, chia seeds, and walnuts.
However, the longer-chain omega-3s, EPA and DHA, are primarily found in fatty fish. The body can convert ALA to EPA and DHA, but the conversion rate is often inefficient.
Source: For vegans, algae-based supplements are a direct source of EPA and DHA.

Iron

Nonheme iron is found in many plant foods, including lentils, spinach, and tofu.
The absorption of nonheme iron can be enhanced by consuming it with vitamin C-rich foods.

Iodine

Iodine levels in plant foods are dependent on the soil.
Source: Iodized salt is the most reliable source for most people, including vegans.

Conclusion: Strategic Planning for Nutritional Needs

For those on a plant-based diet, the question of which vitamins are not found in plants points to the necessity of strategic nutritional planning. The most significant concern is vitamin B12, which is almost entirely absent from plant foods and requires supplementation or consumption of fortified products. Vitamin D, while produced by the body through sun exposure, is also scarce in most plant foods, with fortified milks and UV-treated mushrooms being exceptions. By understanding these nutritional gaps and proactively using fortified foods and high-quality supplements, individuals can ensure a complete and healthy plant-based diet. It is always wise to consult with a healthcare provider or a registered dietitian to monitor nutrient levels and create a personalized plan.

Visit the NIH Office of Dietary Supplements for detailed information on vitamin B12

Frequently Asked Questions

Vitamin B12 is produced by bacteria and archaea, not by plants. This means that animals, including humans, rely on microbial sources, either directly or indirectly through consuming animal products that concentrate the vitamin from bacteria.

Yes, but they are not natural plant foods. The most reliable vegan sources are foods that have been fortified with B12 (such as some cereals and plant-based milks), nutritional yeast, and dietary supplements.

Yes, some mushrooms can produce Vitamin D. When exposed to UV light, either naturally in the wild or intentionally by producers, mushrooms develop Vitamin D2. However, most store-bought mushrooms grown in the dark have little to no Vitamin D.

Yes, supplementation is generally considered necessary for individuals following a vegan diet to prevent deficiency. This is because plant foods do not reliably contain active B12.

A deficiency in vitamin B12 can cause megaloblastic anemia and severe neurological issues, including nerve damage, confusion, and memory loss. Symptoms can be slow to appear due to the body's ability to store the vitamin.

Aside from sun exposure, vegans can obtain Vitamin D from fortified foods like plant milks, certain cereals, and UV-treated mushrooms. Supplements, including vegan Vitamin D3 derived from lichen, are also available and highly reliable.

Lacto-ovo vegetarians, who consume dairy and eggs, typically get some B12 from their diet. However, those following more restrictive vegetarian diets or simply eating low amounts of animal products should still be mindful of their B12 intake and consider fortified foods or supplements.