Vitamin b12 absorption and food
Pro Research Analysisby 
Searched over 200M research papers
Vitamin B12 Absorption and Food Sources
Animal Foods as Primary Vitamin B12 Sources
Vitamin B12 is mainly found in animal-based foods such as meat, milk, eggs, fish, and shellfish. These foods are the most reliable sources because vitamin B12 is synthesized by bacteria and accumulates in animal tissues through microbial interactions, especially in ruminant animals like cattle and sheep. Humans depend on these animal foods to meet their vitamin B12 needs, as plants generally do not contain significant amounts of active vitamin B12 unless they have been contaminated by bacteria or are certain types of edible algae or mushrooms, which are rare exceptions 24810.
Bioavailability and Absorption of Vitamin B12 from Foods
The absorption of vitamin B12 from food is a complex process that requires the presence of intrinsic factor, a protein produced in the stomach. This intrinsic factor binds to vitamin B12 and allows it to be absorbed in the ileum (the last part of the small intestine). The absorption system can become saturated at about 1.5–2.0 micrograms per meal, meaning that taking in more vitamin B12 at once does not lead to much higher absorption 29.
Bioavailability, or the proportion of vitamin B12 that is actually absorbed and used by the body, varies depending on the food source. For example, vitamin B12 from fish, sheep meat, and chicken meat is absorbed at rates of about 42%, 56–89%, and 61–66%, respectively. In contrast, vitamin B12 from eggs is poorly absorbed, with less than 9% being available to the body .
Impact of Food Matrix and Cooking on Vitamin B12 Absorption
The form of vitamin B12 present in foods can affect how well it is absorbed. Foods contain different forms of vitamin B12, such as adenosylcobalamin, hydroxocobalamin, methylcobalamin, and cyanocobalamin. Some forms, like sulphitocobalamin, are absorbed less efficiently than others. Additionally, cooking and storage can degrade vitamin B12, reducing its biological activity and making less of it available for absorption 45.
Plant-Based and Fortified Foods
Most plant foods do not naturally contain active vitamin B12. Some dried seaweeds (like nori) and certain mushrooms may have small amounts, but many edible algae and blue-green algae supplements contain mostly inactive forms (pseudovitamin B12) that do not work in humans. For people who avoid animal products, such as vegans, fortified foods like breakfast cereals and specially enriched vegetables are important sources of vitamin B12. These fortified foods use crystalline vitamin B12, which is more easily absorbed, especially for those with limited intrinsic factor production 248.
Vitamin B12 Supplements and Absorption Efficiency
Vitamin B12 supplements are often used by people at risk of deficiency, such as vegans and the elderly. However, the body absorbs a smaller percentage of vitamin B12 from large supplement doses compared to food sources, due to the saturation of the absorption system. For example, daily supplements containing up to 20 micrograms are unlikely to cause pharmacological effects, while higher doses may be needed for people with absorption problems. When estimating vitamin B12 intake adequacy, it is important to consider how much is actually absorbed, not just the amount consumed 36.
Innovative Food Fortification Approaches
Recent research has explored adding vitamin B12 to foods like yogurt using bacterial fermentation. This method can improve the stability and absorption of vitamin B12, making it a cost-effective way to enhance vitamin B12 intake, especially for people with dietary restrictions or absorption issues .
Conclusion
Vitamin B12 absorption from food depends on the source, the form of the vitamin, and the presence of intrinsic factor in the digestive system. Animal foods are the most reliable sources, while plant-based diets require careful planning with fortified foods or supplements. The efficiency of absorption varies, and both the food matrix and preparation methods can impact how much vitamin B12 the body can use. For those at risk of deficiency, such as vegans and the elderly, fortified foods and appropriate supplementation are essential to maintain adequate vitamin B12 status 246810.
Sources and full results
Most relevant research papers on this topic