VEGAN SOURCES OF VITAMIN B
12
All of the vitamin B
12
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 B
12
in our small intestine; the bacteria producing it live in our large intestine.
There are also molecules that are very similar to vitamin B
12
but that have no true vitamin activity for humans. These are inactive B
12
analogues. Most methods for measuring vitamin B
12
in foods don’t differentiate between true vitamin B
12
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 B
12
. But studies show that what they really contain are primarily inactive analogues.
1
There is a double risk associated with depending on these foods for vitamin B
12
, because the inactive analogues can actually block the activity of true vitamin B
12
.
2
Some companies may claim that a food contains active vitamin B
12
even though the testing methods they use can’t discern between active B
12
and inactive analogues. Currently, the only way to know if a food contains active vitamin B
12
is to feed it to humans and look for vitamin B
12
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 B
12
deficiency, and consuming foods that contain active vitamin B
12
causes those levels to drop. Many foods that are commonly believed to be good sources of vitamin B
12
actually have no effect on MMA levels, which means that they contain primarily inactive analogues.
Plants have no need for B
12
, which is why they usually don’t contain any. Occasionally, a plant food might be “contaminated” with an inactive B
12
analogue. That is, it contains vitamin B
12
by accident. For example, the “starter” used to make tempeh, which is a fermented soyfood, might accidentally contain B
12
-producing bacteria. Seaweed might pick up bacteria that produce B
12
-analogues. There is some evidence that sea vegetables such as chlorella, dulse, and nori contain vitamin B
12
, but again, these haven’t been shown to be reliable and significant sources of the active vitamin.
3
Most humans get vitamin B
12
by eating animal products. Animals such as cows and other true herbivores are able to absorb the vitamin B
12
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 B
12
.
It would follow that soil and water that are contaminated with human or animal waste should contain vitamin B
12
, 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 B
12
was active. A more recent finding that plants could take up vitamin B
12
from manuretreated soil didn’t show whether the B
12
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.
4
Humans definitely evolved to get by on pretty low intakes of vitamin B
12
. 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 B
12
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 B
12
supply. It depends on what your diet has been like over time. Building up generous B
12
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 B
12
stores may be relatively low. Some people may find themselves running through their B
12
supply in just a few months. In addition, vitamin B
12
stores may not be sufficient to prevent mild, marginal-type deficiencies, as we’ll see below.
VITAMIN B
12
DEFICIENCY
Overt deficiency occurs when vitamin B
12
stores drop to near zero. The megaloblastic anemia that occurs with B
12
deficiency is reversible with vitamin B
12
therapy. Sometimes B
12
deficiency anemia is “masked” by the vitamin folic acid (also called folate), which can step in and do vitamin B
12
’s job. So you can be deficient in vitamin B
12
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 B
12
deficiency. If B
12
intake is low and folate intake is high, B
12
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.
5
The neurological damage that can result from a B
12
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 B
12
intake during pregnancy.
The anemia and neurological symptoms associated with overt B
12
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 B
12
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.
6
Elevated homocysteine may also be related to Alzheimer’s disease
7
and neural tube defects in the developing embryo.
8
Research shows that vegetarians and vegans who supplement with vitamin B
12
have healthy levels of homocysteine. Those who don’t take supplements have high homocysteine levels.
9
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 B
6
also affect the vitamin homocysteine, but most vegans get plenty of those.)
While this might sound like vitamin B
12
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 B
12
or don’t want to use supplements or fortified foods.
We think that vegans actually have the advantage when it comes to vitamin B
12
. Here is why: As people age, no matter what type of diet they follow, their ability to absorb vitamin B
12
found naturally in foods begins to decline.
10
Vitamin B
12
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 B
12
from the protein so it can be absorbed. Because the vitamin B
12
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 B
12
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 B
12
supplements or fortified foods.
It has been suggested that anyone who is worried about whether or not they should take supplements should simply get their B
12
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 B
12
levels tested if you want, but regardless of the results, you should follow the advice about vitamin B
12
supplements and fortified foods we’ve outlined below.
MEETING VITAMIN B
12
NEEDS
There are a couple of important things to keep in mind about supplementing with B
12
. First, B
12
supplements should be either chewable or sublingual (dissolving under the tongue) since research shows that, in some people, B
12
isn’t well absorbed from pills that are swallowed whole.
Also, the body is used to getting little bits of vitamin B
12
here and there throughout the day. When confronted with a big dose of B
12
, it absorbs just a tiny fraction of the whole amount. So when you take vitamin B
12
infrequently, you need rather large amounts in order to get enough. The RDA for vitamin B
12
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 B
12
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 B
12
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 B
12
each.
• Take a daily vitamin B
12
supplement of at least 25 micrograms (25 to 100 micrograms is a good range).
• Take a supplement of 1,000 micrograms of vitamin B
12
three times a week.
12
FROM FORTIFIED FOODS
Plant foods are reliable sources of active vitamin B
12
only if they are fortified with the vitamin. On food labels, the Daily Value for vitamin B
12
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 cheesyyeasty 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 B
12
. Red Star brand Vegetarian Support Formula is a good vitamin B
12
–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 B
12
. Neither is the active yeast used in bread making.
VITAMIN B
12
CONTENT OF FORTIFIED VEGAN FOODS
Food
| Vitamin B12 Content (µg)
|
|---|
Nutritional yeast, Vegetarian Support Formula, 1 tablespoon
| 4.0
|
Veggie “meat” analogues, fortified
| 1.0–3.0
|
(varies by brand)
|
Soymilk, fortified, 1 cup
| 1.2–2.9
|
(varies by brand)
|
Protein bar, fortified
| 1.0–2.0
|
(varies by brand)
|
Marmite yeast extract, 1 teaspoon
| 0.9
|
12
FACTS
• The vitamin B
12
in supplements comes from bacterial cultures never from animal products.
• B
12
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 B
12
don’t contain any vitamin B
12
or have only inactive analogues.
• Neither rainwater nor organically grown, unwashed vegetables are a reliable source of vitamin B
12
.
• If you rely on fortified food sources of vitamin B
12
, it is best to have at least two fortified food sources on hand in case a particular batch of a food contains vitamin B
12
that is somehow damaged. Do not rely solely on one type of fortified food.
• About 2 percent of older people can’t absorb B
12
. This disease is called
pernicious anemia
. Being vegan has nothing to do with this condition, but if you are supplementing regularly with vitamin B
12
and still suspect that you have symptoms of vitamin B
12
deficiency, such as extreme fatigue or neurological problems, then by all means get your B
12
levels tested. Pernicious anemia is treated with vitamin B
12
injections.