Fermented Food & B-12

Fermented foods such as miso contain an inactive form of vitamin B-12.
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Vitamin B-12 is essential for good health. There are a lot of ways for people to get enough vitamin B-12, including taking supplements, getting injections or eating foods that are rich in the vitamin. The most common food sources of B-12 are meat, seafood and dairy products, and it can also be found in fermented foods. However, much of the form of B-12 found in fermented foods is not the kind your body can use.

Fermented Foods

Fermenting is a process used to preserve food. It involves bacteria feeding on the natural sugars in foods to create compounds such as lactic acid that help food stay fresh longer. Popular fermented foods include pickles, sauerkraut, yogurt, tempeh, miso and kimchi. Popular fermented beverages include kombucha tea and a yogurtlike drink known as kefir.

How B-12 Is Made

Vitamin B-12 does not occur naturally in the human body, nor is it made naturally by other animals or by plants. Bacteria is responsible for synthesizing vitamin B-12. When animals eat food containing this bacteria, they become a source of B-12 that they pass along to humans who eat animal products.

B-12 in Fermented Foods

Because fermented foods are made with live bacteria and B-12 comes from bacteria, it makes sense that fermented foods would contain vitamin B-12. And, in fact, fermented favorites such as tempeh, miso and sauerkraut do contain a form of B-12. But it is mostly the inactive form -- also called an analogue form -- of the vitamin. Not only is this form not useful to the human body, it can actually interfere with normal absorption and metabolism of the active form of vitamin B-12.

Other Foods

To consume the active form of vitamin B-12 from food sources, look to seafood -- particularly clams, trout, salmon and tuna -- along with beef, milk, yogurt and cheese. Vitamin B-12 is also added to many foods, which are said to be "fortified" with B-12. These foods include processed breads, cereals and grains, as well as soy milk, fake meats and nutritional yeast. Some sea vegetables, such as nori, contain substantial amounts of vitamin B-12, but as with fermented foods, it's the form that is inactive in humans.