But before getting into all this, there is the pesky problem of
definition. What, exactly, is a vegetarian? As it happens, people who
call themselves vegetarians eat many kinds of diets. The least
restrictive vegetarians do not eat beef but occasionally eat pork or
lamb. Next come the groups that eat no red meats, or restrict poultry,
dairy, fish, or eggs. The most restrictive are vegans who eat no foods
of animal origin at all.
Nutritional implications depend on the degree of restriction. The
least restrictive diets, those that exclude meat but include fish,
milk, or eggs, raise no nutritional issues whatsoever. People who eat
such diets are likely to have a lower risk of heart disease and certain
cancers than the average meat-eating American, and a risk of
osteoporosis no higher.
Only the most restrictive vegetarian diets raise nutritional
concerns. Vegans, who eat no foods of animal origin, need to do three
• Find an alternative source for vitamin B12 (supplements or fortified foods).
• Eat enough calories to maintain a good weight.
• Eat a variety of grains and beans to get enough protein.
Vitamin B12 is found only in foods of animal origin--meat, dairy, eggs, or fish. With this one exception, fruits, vegetables, and grains provide plenty of the other vitamins and
minerals. Vegans who obtain enough calories from varied plant food
sources should be taking care of those nutrients as well as protein.
On the protein question: Foods from animals are higher in protein
than those from plants. Their proteins are of somewhat better quality,
meaning that they more closely resemble human proteins. If calories
are adequate, protein is rarely a problem. Protein is hardly lacking
among Americans. The protein requirement is about half a gram for each
pound of body weight, which works out to 55 grams for a 120-pound woman
and 65 grams or so for a 180-pound man. On surveys, women report eating
a daily average of 70 grams of protein, and men 100 grams, and these
amounts are likely to be underestimates. Even vegans get more than
enough protein from grains, beans, and vegetables as long as they get
In relatively unprocessed foods, protein is closely linked to
calories. Diets with enough calories usually contain enough protein
unless the diet is unusually restrictive or includes a lot of junk
food. Think about it: entire civilizations--in ancient Egypt, China,
and Mexico, for example--were based on wheat, rice, beans, or corn as
sources of protein. We used to think that vegetarians had to be
careful to combine plant foods (beans and corn, for example) to get
enough protein but we know now that variety and calories take care of
Developing countries are another matter. In places where food is
scarce, children thrive better when they are fed a little meat (or
dairy, fish, or eggs) along with whatever else they are eating, but a
richer plant-based diet also works well.