Vitamin B12 in a Vegan Diet

vitamin-b12-in-a-vegan-dietYou may have heard that vitamin B12 is a controversial topic among vegans. But among nutrition professionals (including those of us who specialize in vegan diets), there is no controversy at all: All vegans need to take a vitamin B12 supplement or consume foods that are fortified with this nutrient.

Vitamin B12 is needed for cell division and formation of healthy red blood cells. It’s also needed to produce myelin, the protective sheath around nerve fibers. Overt B12 deficiency can produce a condition called macrocytic or megaloblastic anemia, in which blood cells don’t divide and reproduce normally. Deficiency can also result in nerve damage. But because B12 is also involved in metabolism of fat and protein, a marginal intake may increase the risk for certain chronic conditions like heart disease.

The scientific name for vitamin B12 is cobalamin because the B12 molecule contains the mineral cobalt at the center of its structure. Commercial preparations of vitamin B12 used in supplements and fortified foods are called cyanocobalamin. This supplemental form is converted in the body to vitamin B12 coenzymes, which are the compounds needed for B12 activity. Some people prefer to take supplements of vitamin B12 that are already in the form of the coenzyme methylcobalamin, which doesn’t require any conversion for some of its uses. But because there are questions about the stability of methylcobalamin, supplements must contain much higher amounts and there is less available research on their effects on B12 status. The recommendations we make in this chapter are based on supplements and fortified foods that utilize cyanocobalamin.

Vegan Sources Of Vitamin B12

All of the vitamin B12 in the world is made by bacteria, and that includes bacteria living in the digestive tracts of animals and humans. It seems like we could just use what these bacteria produce, but they are too far down in the intestines to be of any use to us. We absorb vitamin B12 in our small intestine; the bacteria producing it live in our large intestine.

There are also molecules that are very similar to vitamin B12 but that have no true vitamin activity for humans. These are inactive B12 analogues. Most methods for measuring vitamin B12 in foods don’t differentiate between true vitamin B12 and the inactive analogues. That’s been a source of confusion for a long time. Foods like fermented soy products, tofu, sourdough bread, and some sea vegetables have all been credited at one time or another as good sources of vitamin B12. But studies show that what they really contain are primarily inactive analogues.  There is a double risk associated with depending on these foods for vitamin B12, because the inactive analogues can actually block the activity of true vitamin B12.

Some companies may claim that a food contains active vitamin B12 even though the testing methods they use can’t discern between active B12 and inactive analogues. Currently, the only way to know if a food contains active vitamin B12 is to feed it to humans and look for vitamin B12 activity. The standard way to do this is to see how different foods affect levels of a compound called methylmalonic acid (MMA). MMA levels increase in B12 deficiency, and consuming foods that contain active vitamin B12 causes those levels to drop. Many foods that are commonly believed to be good sources of vitamin B12 actually have no effect on MMA levels, which means that they contain primarily inactive analogues.

Plants have no need for B12, which is why they usually don’t contain any. Occasionally, a plant food might be “contaminated” with an inactive B12 analogue. That is, it contains vitamin B12 by accident. For example, the “starter” used to make tempeh, which is a fermented soy-food, might accidentally contain B12-producing bacteria. Seaweed might pick up bacteria that produce B12-analogues. There is some evidence that sea vegetables such as chlorella, dulse, and nori contain vitamin B12, but again, these haven’t been shown to be reliable and significant sources of the active vitamin.

Most humans get vitamin B12 by eating animal products. Animals such as cows and other true herbivores are able to absorb the vitamin B12 produced in their intestines by bacteria. Others, including many primate species, eat at least small amounts of animal products (including insects) or feces, which can be a good source of B12.

It would follow that soil and water that are contaminated with human or animal waste should contain vitamin B12, and they might. But while there is speculation about this among research scientists, there is no direct evidence for it. One paper that has gained support among some vegan groups was actually just an abstract in Science magazine from 1950 by researchers with the New York Botanical Gardens. The methods used didn’t determine whether the B12 was active. A more recent finding that plants could take up vitamin B12 from manure-treated soil didn’t show whether the B12 was active vitamin or inactive analogue. And it doesn’t really matter because the amounts were so tiny that they didn’t have any nutritional significance.

Humans definitely evolved to get by on pretty low intakes of vitamin B12. We have a rather complex physiological way of recycling it, and we also can store relatively large amounts in our livers—sometimes enough to prevent overt deficiency for as long as three years. As a result, some vegan advocates insist that no one needs to worry about vitamin B12 until they have been a vegan for several years and that we can get by with taking supplements just “once in a while.” We think this approach is a mistake for a couple of reasons.

First, not everyone has a three-year B12 supply. It depends on what your diet has been like over time. Building up generous B12 stores can take many years of consuming the vitamin in quantities that exceed daily needs. If you have been eating a mostly plant-based or lacto-ovo vegetarian diet before becoming vegan—that is, a diet that is more moderate in animal foods than what most Americans eat—your vitamin B12 stores may be relatively low. Some people may find themselves running through their B12 supply in just a few months. In addition, vitamin B12 stores may not be sufficient to prevent mild, marginal-type deficiencies, as we’ll see below.

Vitamin B12 Deficiency

Overt deficiency occurs when vitamin B12 stores drop to near zero. The megaloblastic anemia that occurs with B12 deficiency is reversible with vitamin B12 therapy. Sometimes B12 deficiency anemia is “masked” by the vitamin folic acid (also called folate), which can step in and do vitamin B12’s job. So you can be deficient in vitamin B12 but not have anemia if your diet is high in folate.

This may sound like a good thing, but it’s not since folic acid won’t prevent the nerve damage that can occur with B12 deficiency. If B12 intake is low and folate intake is high, B12 deficiency can go unnoticed until it progresses to a more advanced stage. It’s an important issue for vegans since they typically have a high intake of folate, which is found in leafy greens, oranges, and beans.

The neurological damage that can result from a B12 deficiency typically begins with tingling in the hands and feet and can progress to far more serious symptoms. Often the symptoms can be reversed, but some neurological damage can be permanent. This is especially true in babies born to mothers who don’t have adequate vitamin B12 intake during pregnancy.

The anemia and neurological symptoms associated with overt B12 deficiency are fairly obvious. But a second type of “mild” deficiency doesn’t have acute symptoms. It does its damage over time—often decades—and is only detected through medical tests. When B12 levels in the blood start to drop, levels of an amino acid called homocysteine begin to rise. Homocysteine may damage blood vessels and nervous tissue and many studies have linked high levels to an increased risk for heart disease, stroke, and early death. Elevated homocysteine may also be related to Alzheimer’s disease7 and neural tube defects in the developing embryo.

Research shows that vegetarians and vegans who supplement with vitamin B12 have healthy levels of homocysteine. Those who don’t take supplements have high homocysteine levels. These findings present strong evidence that vegans who don’t use supplements—and who insist that they feel fine—may be damaging their health over the long term. (Folate and vitamin B6 also affect the vitamin homocysteine, but most vegans get plenty of those.)

While this might sound like vitamin B12 is a big problem for vegans, it’s an issue that’s so easily resolved it shouldn’t be a concern. In fact, it’s a concern only when vegans don’t get good advice about vitamin B12 or don’t want to use supplements or fortified foods.

We think that vegans actually have the advantage when it comes to vitamin B12. Here is why: As people age, no matter what type of diet they follow, their ability to absorb vitamin B12 found naturally in foods begins to decline.10 Vitamin B12 in animal foods is bound to protein, and the decrease in stomach acid that tends to occur in older people makes it harder to release B12 from the protein so it can be absorbed. Because the vitamin B12 in supplements and fortified foods is not bound to protein, it is more easily absorbed by older people. For this reason, the FNB recommends that all people over age fifty get at least half of the RDA for B12 from some combination of supplements and fortified foods. Many older people may not know this, but vegans who are paying attention to good nutrition advice are already using vitamin B12 supplements or fortified foods.

Supplementing Versus Monitoring

It has been suggested that anyone who is worried about whether or not they should take supplements should simply get their B12 levels tested. But that doesn’t make any sense. You don’t want to wait until your levels are low to start supplementing. And if your levels are normal, you should supplement in order to maintain them. There is no reason not to take supplements. They are inexpensive and safe. So you can have your B12 levels tested if you want, but regardless of the results, you should follow the advice about vitamin B12 supplements and fortified foods we’ve outlined below.

Meeting Vitamin B12 Needs

There are a couple of important things to keep in mind about supplementing with B12. First, B12 supplements should be either chewable or sublingual (dissolving under the tongue) since research shows that, in some people, B12 isn’t well absorbed from pills that are swallowed whole.

Also, the body is used to getting little bits of vitamin B12 here and there throughout the day. When confronted with a big dose of B12, it absorbs just a tiny fraction of the whole amount. So when you take vitamin B12 infrequently, you need rather large amounts in order to get enough. The RDA for vitamin B12 is just 2.4 micrograms for adults. But if you are getting your daily dose from a supplement, you may need as much as 25 to 100 micrograms. And if you supplement just two or three times a week, you may need 1,000 micrograms each time.

If you have not had a regular source of vitamin B12 for some time, we recommend taking 2,000 micrograms every day for two weeks before beginning the regular supplementation schedule as follows.

To meet your vitamin B12 requirements on a vegan diet do any one of the following:

  • Consume two servings per day of fortified foods providing 1.5 to 2.5 micrograms of vitamin B12 each.
  • Take a daily vitamin B12 supplement of at least 25 micrograms (25 to 100 micrograms is a good range).
  • Take a supplement of 1,000 micrograms of vitamin B12 three times a week.

 Getting B12 From Fortified Foods

Plant foods are reliable sources of active vitamin B12 only if they are fortified with the vitamin. On food labels, the Daily Value for vitamin B12 is 6 micrograms. So if a food provides 25 percent of the Daily Value, it contains 1.5 micrograms.

Nutritional yeast is a popular choice with many vegans. Its cheesy-yeasty flavor is great mixed into bean and grain dishes or sprinkled over popcorn. Nutritional yeast is grown on a nutrient-rich culture and contains only the nutrients that are in that culture. So don’t assume that every type of nutritional yeast is a good source of vitamin B12. Red Star brand Vegetarian Support Formula is a good vitamin B12-rich choice that is widely available, often in the bulk food section of natural foods markets. Brewer’s yeast is a by-product of beer making and is not a good source of vitamin B12. Neither is the active yeast used in bread making.


Vitamin B12 Facts

  • The vitamin B12 in supplements comes from bacterial cultures— never from animal products.
  • B12 pills should be chewed or allowed to dissolve under the tongue.
  • Seaweed (e.g., algae, nori, spirulina), brewer’s yeast, tempeh, or “living” vitamin supplements that use plants as a source of B12 don’t contain any vitamin B12 or have only inactive analogues.
  • Neither rainwater nor organically grown, unwashed vegetables are a reliable source of vitamin B12.
  • If you rely on fortified food sources of vitamin B12, it is best to have at least two fortified food sources on hand in case a particular batch of a food contains vitamin B12 that is somehow damaged. Do not rely solely on one type of fortified food.
  • About 2 percent of older people can’t absorb B12. This disease is called pernicious anemia. Being vegan has nothing to do with this condition, but if you are supplementing regularly with vitamin B12 and still suspect that you have symptoms of vitamin B12 deficiency, such as extreme fatigue or neurological problems, then by all means get your B12 levels tested. Pernicious anemia is treated with vitamin B12 injections.

Is A Vegan Diet Natural?

It wouldn’t be right to ignore the four-hundred-pound gorilla in the room, so let’s ask the obvious question: Since vitamin B12 is not found in plant foods and vegans must take supplements, doesn’t that make a vegan diet unnatural?

Many vegans have bent over backwards to convince themselves and others that humans evolved as vegans and that supplemental vitamin B12 is only needed because we have moved so far away from our natural environment. But there is a tremendous amount of evidence that humans evolved eating some animal products. While B12 is not needed in large amounts, it may take more than can be picked up from unwashed produce to sustain optimal levels. That’s especially true during pregnancy and lactation, when a woman needs to consume enough B12 for her own needs and to pass on to her baby.

In fact, adding small amounts of animal products to the diet has been shown not to cure B12 deficiency. At least one study showed that some lacto-ovo vegetarians may have vitamin B12 status that is similar to that of vegans when neither group supplemented. If consuming small amounts of animal foods doesn’t improve vitamin B12 status, then it is unlikely that inadvertently ingesting B12 from unwashed produce would be enough to sustain vegans through the life cycle in a pre- vitamin-supplement culture.

Paleontology student Robert Mason, who writes the PaleoVeganology website, says this about the evolution of human diets: “This touches on the issue of how vegans should handle the caveman argument. Many of us are tempted to strain credulity and torture the evidence to ‘prove’ humans are ‘naturally’ vegan. This is a trap, and one into which carnists (especially paleo-dieters) would love us to fall; the evidence isn’t on our side. There’s no doubt that hominids ate meat. . . . The argument for veganism has always been primarily ethical, and ought to remain that way. It’s based on a concern for the future, not an obsession about the past.”

And Tom Billings, who writes the Beyond Veg website, says, “Further, if the motivation for your diet is moral and/or spiritual, then you will want the basis of your diet to be honest as well as compassionate. In that case, ditching the false myths of naturalness presents no problems; indeed, ditching false myths means that you are ditching a burden.”

We agree that it just doesn’t matter whether a vegan diet is our historical way of eating or not. The fact is, it makes sense now to choose a vegan diet. And whose diet is really natural, anyway? The assumption that there is one natural prehistoric diet, which can be approximated today and would be optimal for modern humans, is dubious at best.

Today’s commercial plant foods and meats are different from the foods available in prehistoric times. We eat hybrids of plants and we feed foods to animals that they would not normally eat. Additionally, the U.S. food supply is routinely fortified with a host of vitamins and minerals. Even those people who strive to eat a more “natural” diet as adults have normally benefited from fortified foods as children. It is quite unlikely that anyone is eating a natural diet in today’s world.

Taking a daily vitamin B12 supplement is a small thing that can make all the difference in your health as a vegan. Based on our current knowledge of vitamin B12 requirements and sources, supplementation is not a subject for debate. Vitamin B12 supplements or fortified foods are an essential part of a well-balanced and responsible vegan diet at all stages of the life cycle.

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