Vegan Nutrition with Brenda Davis

Brenda Davis is a registered dietitian in private practice. She is the past Chair of the Vegetarian Nutrition Dietetic Practice Group of the American Dietetic Association. Brenda is co-author of the international best seller, Becoming Vegetarian, and highly acclaimed Becoming Vegan. Brenda is an internationally recognized speaker. She has worked as a public health nutritionist, a clinical nutrition specialist, nutrition consultant and academic nutrition instructor.

Question:

Regarding B12, I've heard we can and I've heard we can't absorb it from things like sea vegetables, tempeh, tofu, and fortified soy beverages. Which story is true? What are REAL sources of B12 vegans should eat that we can actually absorb?

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Answer:

Vitamin B12 is a nutrient that we simply can't afford to mess around with, especially where infants and young children are concerned. It is untrue that we can't absorb it from sea vegetables, tempeh, tofu and fortified soy beverages, but that doesn't mean that all of these foods are reliable B12 sources. Many of the foods traditionally used by vegetarians for vitamin B12 (fermented soyfoods, seaweeds and organic vegetables) may provide some vitamin B12, but for a variety of reasons should not be counted on to provide sufficient amounts of this important nutrient.

In fermented foods such as tempeh and miso the amounts of vitamin B12 are highly variable, depending on method of fermentation used. In the past, fermentation was done slowly using wooden vats. Vitamin B12 was often significant in using this method because the wooden vats were contaminated with B-12-producing bacteria, and the slow fermentation allowed airborne bacteria to drift in. Today, fermentation is much faster and scrupulously clean, stainless steel vats are often used, thus B12 content is generally much lower.

Seaweeds do contain some vitamin B12, however, they also contain molecules that look like vitamin B12, but are unable to perform the essential functions of this nutrient. These molecules (called non-cobalamin corrinoids or B12 analogs) can occupy vitamin B12 receptor sites potentially interfering with the action of true B12. At the present time we don't have enough information about the actual vitamin B12 vs. B12 analogs in various seaweeds (although it appears that dried seaweeds contain primarily B12 analogs). Until that information is available, seaweeds should not be relied upon as B12 sources.

Organic vegetables may have vitamin B12 on them but not in them. Generally people wash vegetables before eating them, and any B12 present goes down the drain with the dirt, thus we cannot count on these foods as sources of B12.

Tofu and unfortified soymilks do not naturally contain vitamin B12, although non-dairy beverages are often fortified with this nutrient. Vitamin B12 used in the fortification of foods is pharmaceutical-grade B12, which is well absorbed by the body and is a very reliable source of this nutrient.

Commonly fortified foods include Red Star Nutritional Yeast (Vegetarian Support Formula), fortified non-dairy beverages, meat analogs and several breakfast cereals (read label). Aim for about 2-3 mcg per day. If fortified foods are not used, you must use a supplement.

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