Vegan for Life - Jack Norris [15]
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.5
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.6 Elevated homocysteine may also be related to Alzheimer’s disease7 and neural tube defects in the developing embryo.8
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.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 B6 also affect the vitamin homocysteine, but most