Which Foods Have Intrinsic Factors? The Answer May Surprise You

November 22, 2025 •

3 min read

Approximately 10-15% of individuals over 60 have difficulty absorbing vitamin B12, a process that relies heavily on intrinsic factor, a protein produced by the stomach. The surprising truth is that no foods contain intrinsic factors; instead, they provide the vitamin B12 that this protein helps your body absorb.

Quick Summary

Intrinsic factor is a protein made in the stomach, not present in food. It is vital for absorbing vitamin B12. Essential B12 sources include animal products and fortified foods, which supply the nutrient intrinsic factor needs.

Key Points

Intrinsic Factor is Internal: Intrinsic factor is a glycoprotein made by parietal cells in your stomach, not a nutrient found in any food.
Facilitates B12 Absorption: Its purpose is to bind to vitamin B12 from food, protecting it and allowing its absorption in the small intestine.
Key B12 Sources: Foods rich in vitamin B12 include meat, liver, poultry, fish, shellfish, eggs, and dairy products.
Fortified Options for Vegans: For plant-based diets, reliable sources of B12 are fortified foods like cereals, plant-based milks, and nutritional yeast.
Intrinsic Factor Deficiency: A lack of intrinsic factor leads to pernicious anemia, a vitamin B12 malabsorption condition that requires medical intervention, not just dietary changes.
Signs of Deficiency: Vitamin B12 deficiency can cause fatigue, nerve issues, and other serious health problems if left untreated.

What Is Intrinsic Factor and Why Isn't It in Food?

One of the most common nutritional misconceptions is that intrinsic factor is found in certain foods. The reality is that intrinsic factor (IF) is a glycoprotein produced by the parietal cells in the stomach lining. Its sole function is to bind with dietary vitamin B12 (also known as cobalamin) so that the body can absorb it in the final part of the small intestine, the terminal ileum. The intrinsic factor protein itself is never ingested; it is a digestive aid produced internally.

The Crucial Role of Intrinsic Factor

When you consume food containing vitamin B12, several steps must occur for it to be absorbed effectively. First, stomach acid and digestive enzymes release the vitamin from its food-bound protein. In the stomach, B12 temporarily binds to another protein called haptocorrin. As this complex moves into the small intestine, pancreatic enzymes break down the haptocorrin, freeing the B12 to bind with the waiting intrinsic factor. The newly formed B12-IF complex is then absorbed via specialized receptors in the terminal ileum. Without this chain of events, and specifically without intrinsic factor, the vast majority of dietary B12 passes through the body unabsorbed.

Foods Rich in Vitamin B12: What Intrinsic Factor Needs

Since you cannot eat intrinsic factor, the best dietary strategy is to consume foods rich in vitamin B12, ensuring your body has plenty of the nutrient it needs. The primary sources of B12 are animal-based, but many plant-based foods are now fortified to help meet daily requirements.

Animal-Based Sources of B12

Meat: Beef, especially beef liver, is one of the densest sources of vitamin B12. Other meats like turkey and chicken also contain good amounts.
Fish and Shellfish: Excellent sources include clams, oysters, salmon, trout, and tuna.
Dairy Products: Milk, cheese, and yogurt are all contributors to B12 intake for those who consume dairy.
Eggs: The vitamin B12 in eggs is concentrated in the yolk, making whole eggs a decent source.

Fortified Foods and Plant-Based B12 Sources

For vegans, vegetarians, and those looking to reduce animal product consumption, fortified foods are a reliable way to get vitamin B12.

Fortified Cereals: Many breakfast cereals have B12 added during manufacturing, with some brands providing a significant portion of the daily value.
Nutritional Yeast: This popular vegan condiment is often fortified with B12 and can be sprinkled on a variety of dishes for a cheesy flavor.
Plant-Based Milks: Soy, almond, oat, and rice milks are commonly fortified with vitamin B12, providing a helpful daily boost.
Vegan Spreads and Alternatives: Some meat and dairy substitutes are also fortified with B12.

Comparison of B12 Sources


Source Category	Examples	Intrinsic Factor or Vitamin B12?	Vegan-Friendly?
Animal Products	Beef liver, salmon, clams, eggs, milk	Provides Vitamin B12	No
Fortified Foods	Breakfast cereal, nutritional yeast, plant milk	Provides Fortified Vitamin B12	Yes
Intrinsic Factor	Parietal cells in the stomach lining	Produces Intrinsic Factor	N/A (Internal)

What If Your Body Lacks Intrinsic Factor?

The inability to produce or properly utilize intrinsic factor leads to a vitamin B12 deficiency, most notably a condition called pernicious anemia. This autoimmune disorder causes the body's immune system to attack and destroy the parietal cells in the stomach, or to create antibodies that block the intrinsic factor itself. Other factors that can interfere with intrinsic factor production and function include certain gastric surgeries, long-term use of acid-blocking medication, or autoimmune gastritis. In these cases, dietary changes alone are not enough to correct the deficiency, and supplementation through injections or high-dose oral tablets is required.

Conclusion

In summary, the key takeaway is that intrinsic factor is a protein your body produces in the stomach to aid in the absorption of vitamin B12. It is not an ingredient in food. To ensure proper B12 absorption, maintaining a healthy gut is crucial, and eating a diet rich in B12 from animal products or fortified plant-based foods is essential. If you suspect an intrinsic factor deficiency, consulting a healthcare provider for a diagnosis and appropriate supplementation is the correct course of action, as diet cannot fix this specific issue. To learn more about Vitamin B12, refer to resources like the NIH Office of Dietary Supplements: Vitamin B12 - Health Professional Fact Sheet.

Frequently Asked Questions

No foods contain intrinsic factor. It is a protein your stomach produces to bind with vitamin B12, which is present in certain foods. The idea that intrinsic factor can be obtained from diet is a common misconception.

Intrinsic factor is a protein made in your stomach, while vitamin B12 (cobalamin) is a nutrient found in food. Intrinsic factor and vitamin B12 must bind together to allow the vitamin to be absorbed into your bloodstream.

The best food sources of vitamin B12 are animal products, including organ meats like beef liver, shellfish such as clams and oysters, fish like salmon and tuna, and fortified cereals and nutritional yeast for vegans.

Yes, but it requires careful planning. Since B12 is primarily in animal products, vegetarians and especially vegans must rely on fortified foods (like plant-based milks and cereals) or supplements to get enough vitamin B12.

If a person lacks intrinsic factor, they cannot absorb vitamin B12 from food, even if they eat B12-rich foods. This leads to a severe deficiency, often diagnosed as pernicious anemia, which can cause significant neurological and hematological issues.

Deficiency caused by a lack of intrinsic factor is typically treated with vitamin B12 injections or high-dose oral supplements. Dietary changes alone are not sufficient, as the absorption pathway is compromised.

Intrinsic factor deficiency is often due to an autoimmune condition and cannot be cured or improved with diet. However, maintaining overall gastric health and avoiding certain risk factors like chronic acid blocker use can support the digestive system.