How do vegetarians obtain vitamin B12 (cobalamin)?

From the Guidelines

Vegetarians should supplement their diets with reliable sources of vitamin B12, such as fortified foods or supplements, to prevent deficiency and related health problems. According to the most recent and highest quality study 1, a diet low in vitamin B12, such as a vegan diet, is a common risk factor for vitamin B12 deficiency. Vegetarians can obtain vitamin B12 through several dietary sources, including dairy products and eggs for lacto-ovo vegetarians, and fortified foods like nutritional yeast, plant milks, breakfast cereals, and meat substitutes for those who avoid all animal products. However, supplements are often necessary, with cyanocobalamin being the most common and effective form 1. A typical adult needs 2.4 micrograms daily, which can be met through a daily supplement of 25-100 micrograms or a weekly supplement of 2000 micrograms.

Some key points to consider:

• Vitamin B12 is essential for nerve function, DNA synthesis, and red blood cell formation
• The body cannot produce B12, and plants don't naturally contain it since it's made by bacteria
• Regular B12 intake is crucial for vegetarians to prevent deficiency, which can lead to anemia, neurological damage, and other health problems 1
• Certain populations, such as pregnant women, children, and adolescents, are at higher risk for B12 deficiency and may require closer monitoring and supplementation 1

In terms of specific recommendations, vegetarians who avoid all animal products should consider taking a daily supplement of 25-100 micrograms of cyanocobalamin or a weekly supplement of 2000 micrograms. Additionally, fortified foods like nutritional yeast, plant milks, breakfast cereals, and meat substitutes can provide reliable B12. It's also important to note that some medications, such as metformin, can increase the risk of B12 deficiency, and vegetarians taking these medications should be closely monitored and supplemented as needed 1.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Sources of Vitamin B12 for Vegetarians

• Vitamin B12 is found almost exclusively in animal-based foods, making it a nutrient of potential concern for vegetarians 2
• Some plant-based foods, such as certain types of dried lavers (nori) and mushrooms, contain substantial amounts of vitamin B12 3, 4
• Dried purple laver (nori) is a suitable vitamin B12 source for vegetarians, as it contains high levels of vitamin B12 and other nutrients lacking in vegetarian diets 4

Vitamin B12 Deficiency and Supplementation

• Vitamin B12 deficiency can be caused by inadequate intake, inadequate bioavailability, or malabsorption 5
• Diagnostic biomarkers for vitamin B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid 5, 6
• Management of vitamin B12 deficiency depends on supplementation, either via high-dose oral routes or parenteral administration 5
• Vegetarians may require vitamin B12-fortified foods or supplements to prevent deficiency 2

Assessment and Diagnosis of Vitamin B12 Status

• A useful process for assessing vitamin B12 status includes taking a diet history, testing serum vitamin B12 level, and testing homocysteine, holotranscobalamin II, or methylmalonic acid serum levels 2
• Serum B12 is still the most commonly used test, but diagnostics by holotranscobalamin, serum methylmalonic acid, and plasma homocysteine measurements are also used 6
• The lack of a robust absorption test and compromised sensitivity and specificity of other tests can hinder determination of the cause of depleted B12 status 6