Which Vitamins Come From Animals? A Guide to Nutrient Sources

November 21, 2025 •

3 min read

Over 90% of the naturally occurring vitamin B12 in the human diet comes from animal-based foods, underscoring their importance as a source for specific nutrients. While many vitamins can be obtained from plants, several key vitamins come from animals, presenting significant dietary considerations for vegans and vegetarians.

Quick Summary

Several key vitamins are predominantly or exclusively found in animal products, including Vitamin B12, Vitamin D3, and preformed Vitamin A (Retinol). These nutrients are vital for nerve function, bone health, and vision. Their higher bioavailability from animal sources makes them a critical dietary component, particularly for individuals not relying on fortified foods or supplements. Other nutrients, like Coenzyme Q10 and Choline, also have rich animal sources.

Key Points

Vitamin B12 is Exclusively Animal-Sourced: Naturally present only in animal products like meat, fish, and dairy, as it is produced by bacteria.
Vitamin D3 is More Bioavailable than D2: Found in animal fats, D3 (cholecalciferol) from sources like fish and egg yolks is more efficiently used by the body than plant-based D2.
Preformed Vitamin A (Retinol) is Animal-Based: The active form of Vitamin A is found in liver, eggs, and dairy, offering higher bioavailability than plant-based carotenoids.
Heme Iron is Only Found in Animal Products: This form of iron is absorbed more efficiently than the non-heme iron found in plants.
Choline is Rich in Animal Foods: Essential for brain health, some of the highest dietary concentrations are found in eggs and organ meats.
Vegans Must Strategically Supplement or Rely on Fortified Foods: Individuals avoiding all animal products need to consciously source nutrients like B12 and D3 through fortified items or supplementation to prevent deficiency.
Organ Meats are Nutrient Powerhouses: Internal organs such as liver and kidneys are especially dense with vitamins like B12, D3, and Retinol.

Vitamins Exclusively or Primarily Found in Animal Products

While a balanced diet should include both plant and animal foods, certain vitamins are naturally concentrated in animal products. This is particularly relevant for those on plant-based diets, who must seek reliable fortified alternatives or supplements to prevent deficiencies. Understanding which vitamins come from animals is key to comprehensive nutrition.

Vitamin B12 (Cobalamin)

Vitamin B12 is arguably the most well-known vitamin found almost exclusively in animal-based foods. It is not produced by plants, but by certain bacteria, which animals then absorb into their tissues or acquire from their food. B12 is essential for red blood cell formation, neurological function, and DNA synthesis. Organ meats like liver and kidneys are exceptionally rich sources, with a 3-ounce serving of cooked beef liver providing well over the daily recommended amount. Other good sources include fish, beef, eggs, and dairy.

Vitamin D3 (Cholecalciferol)

While sunlight exposure is the primary way humans produce Vitamin D, dietary sources are crucial, especially in regions with limited sunlight. The two main dietary forms are D2 (from plants/fungi) and D3 (from animal foods). Research suggests that Vitamin D3 is more effective at raising and sustaining blood vitamin D levels than D2. Fatty fish (salmon, mackerel), fish liver oils, and egg yolks are among the best animal-derived sources.

Preformed Vitamin A (Retinol)

Dietary Vitamin A comes in two forms: preformed Vitamin A (retinol) from animal products and provitamin A carotenoids (like beta-carotene) from plants. The body must convert carotenoids into retinol, but this process can be inefficient. Preformed Vitamin A from animal sources, such as liver, fish, and dairy, is ready for the body to use directly. This active form is crucial for vision, immune function, and cell growth.

Other Animal-Sourced Nutrients and Compounds

Beyond these core vitamins, several other important compounds are found in abundance in animal products:

Choline: An essential nutrient vital for brain health and liver function, with animal foods like eggs, beef, and chicken containing the highest concentrations.
Coenzyme Q10 (CoQ10): A vitamin-like compound with antioxidant properties. It is highest in organ meats, fatty fish, and beef.
Heme Iron: The form of iron found exclusively in animal flesh (meat, poultry, fish). Heme iron is more easily absorbed by the body than non-heme iron from plants.

Comparison of Animal vs. Plant Vitamin Bioavailability

Bioavailability refers to the proportion of a nutrient that is absorbed and utilized by the body. Animal sources often have a distinct advantage in this regard for certain vitamins.


Feature	Animal-Sourced Vitamins (B12, D3, Retinol, Heme Iron)	Plant-Sourced Vitamins (D2, Beta-carotene, Non-heme Iron)
Absorption Rate	Generally higher; nutrients are in readily usable forms.	Can be lower; conversion processes are required, and absorption can be hindered by other plant compounds.
Interference	Minimal interference from other components.	Absorption can be affected by phytates in beans and grains, which can inhibit the uptake of minerals.
Conversion Efficiency	No conversion needed for preformed nutrients like retinol and D3.	Conversion of carotenoids to Vitamin A can vary greatly among individuals based on genetics.

Potential Deficiencies and Dietary Planning

For those who exclude animal products, strategic dietary planning or supplementation is necessary to avoid nutrient deficiencies, particularly for Vitamin B12. Fortified foods and supplements are reliable alternatives, but an awareness of one's intake is critical. The long-term effects of deficiencies in B12, Vitamin D, or other animal-derived nutrients can include neurological issues, anemia, and compromised immune function. Consulting with a healthcare provider or registered dietitian is advisable to ensure a nutritionally complete diet, regardless of your dietary choices.

Conclusion

Animal products serve as vital and highly bioavailable sources for several crucial vitamins, including the famously animal-exclusive Vitamin B12, the more potent Vitamin D3, and preformed Vitamin A (retinol). While plant-based diets offer a wide array of other health benefits and vitamins, they do not provide these specific nutrients in their most readily usable form, or at all in the case of B12. Understanding which vitamins come from animals empowers individuals to make informed dietary choices, whether through including animal products, consuming fortified foods, or supplementing to meet their nutritional needs effectively.

Frequently Asked Questions

The most notable vitamin found exclusively in animal products and fortified foods is Vitamin B12. The most potent natural forms of Vitamin D (D3) and Vitamin A (Retinol) are also primarily from animal sources.

Plants do not produce Vitamin B12. It is produced by certain bacteria that are consumed by animals. Thus, B12 is naturally stored in animal tissues and passed on to humans through meat, dairy, and eggs.

For certain vitamins like B12, D3, and preformed Vitamin A (Retinol), the forms found in animal products are more readily absorbed and utilized by the body, a concept known as higher bioavailability. However, both plants and animals are necessary for a complete range of vitamins.

Vitamin D2 comes from plants and fungi, while Vitamin D3 is naturally found in animal products and is synthesized in human skin from sunlight. Studies suggest that Vitamin D3 is more effective at raising and maintaining blood vitamin D levels.

Vegans need to obtain Vitamin B12 from fortified foods like cereals, nutritional yeast, and plant-based milks, or from supplements. Vegan-friendly Vitamin D3 supplements derived from lichen are also available. Regular blood tests can help monitor nutrient levels.

Organ meats, such as beef liver and kidneys, are some of the richest sources of Vitamin B12. Other excellent sources include clams, fatty fish like salmon and trout, and beef.

No, a balanced diet requires both plant and animal foods. Plant foods are the main source of Vitamin C, provitamin A carotenoids, and many other essential compounds not found in animal products.