Vegan for Life (5 page)

It’s easy to build meals that pack a substantial protein punch. Each of these meals provides at least 20 grams of protein.

Overt protein deficiency is rare among Americans and occurs in other parts of the world where people don’t have enough food. Many vegan advocates point out that people don’t end up in hospitals because of a protein deficiency. It’s true that in countries where food is abundant, acute deficiency of protein doesn’t occur. But diets that are marginal in protein—not quite deficient, but not quite optimal—can result in loss of muscle mass, poor bone health, and compromised immunity. And those kinds of problems do occur in the United States.

We’d like to say that vegans never need to worry about protein, but that isn’t entirely true. There are a few situations where vegans may fall short on meeting their protein needs.

Vegan diets that are low in protein-rich foods like legumes are likely to be too low in protein. And because low-calorie diets raise protein requirements, people who are dieting or simply not eating enough for other reasons (like chronic illness) may need to boost their intake of protein-rich foods like legumes or soyfoods.

Obviously, junk-food vegan diets—those based on potato chips, French fries, and soft drinks—can be too low in protein (and too low in just about everything else that you need to be healthy).

And extreme versions of vegan diets, such as raw foods or fruitarian regimens, are often low (or completely lacking) in the higher-protein plant foods like legumes and soyfoods and can lead to a marginal protein intake. That’s one reason these types of diets are not recommended for children.

One common belief, often voiced by critics of vegan diets, is that plant foods don’t provide adequate tryptophan. This essential amino acid is needed to make the neurotransmitter serotonin, and low levels of serotonin are linked to depression. Meat is higher in tryptophan
than plants, but a well-balanced vegan diet is almost guaranteed to provide more than enough of this amino acid. The FNB recommends 5 milligrams of tryptophan for every kilogram of healthy body weight. Adding in a factor for plant protein digestion, this translates to a vegan RDA of 5.5 milligrams per kilogram of body weight or 2.5 milligrams of tryptophan per pound.

For example, a vegan who weighs 130 pounds would need 325 milligrams of tryptophan, which is easily provided on a vegan diet. A diet that includes one cup of black beans, ½ cup of tofu and one cup of brown rice would provide nearly 400 milligrams of tryptophan.

In fact, eating foods that are very high in protein, like meat, doesn’t necessarily increase the amount of tryptophan in the brain. That’s because high levels of other amino acids in these foods block absorption of tryptophan from the blood into the brain. Eating foods like legumes that provide both protein and carbohydrates can actually enhance the passage of tryptophan into the brain.
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Y
ou may have heard that vitamin B
₁₂
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 B
₁₂
supplement or consume foods that are fortified with this nutrient.

Vitamin B
₁₂
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 B
₁₂
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 B
₁₂
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 B
₁₂
is cobalamin because the B
₁₂
molecule contains the mineral cobalt at the center of its structure. Commercial preparations of vitamin B
₁₂
used in supplements and fortified foods are called cyanocobalamin. This supplemental form is converted in the body to vitamin B
₁₂
coenzymes, which are the compounds needed for B
₁₂
activity. Some people prefer to take supplements of vitamin B
₁₂
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 B
₁₂
status. The recommendations we make in this chapter are based on supplements and fortified foods that utilize cyanocobalamin.