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Legumes
The 13,000 different varieties of
legumes that are grown worldwide share two major characteristics -- they all
produce seed-bearing pods, and have nodules on their roots, which harbor
bacteria that can convert atmospheric nitrogen to nitrate, a form of
nitrogen the plant uses for nutrition. Otherwise, these members of the
Leguminosae plant family differ greatly: some are low-growing plants (bush
beans, lentils, and soybeans) or vines (many peas and beans); other s are
trees (carob) or shrubs (mesquite). Although peanuts are often classified as
nuts, they are actually legumes; so too are clover and alfalfa, two major
haycrops, and fenugreek.
Archeologists have found evidence
that beans and peas were cultivated in Southeast Asia some 11,000 years ago,
which may mean that they were actually grown before grains. Chickpeas, fava
(broad) beans, and lentils have been cultivate in the Middle East since
about 8000 BC and beans have been grown in the New World since 4000 BC. The
European colonists noted that Native people grew beans between rows of corn.
A the time, they believed that this was to reduce weed growth; we now know
that most legumes replenish the soil with nitrogen, a nutrient depleted by
corn and other grains.
Because legumes may lack certain
amino acids (the building blocks of protein), it has been thought that these
foods must be eaten at the same time as other food which contain the missing
amino acids to provide a "complete" protein. For example, a combining beans
and corn to make the popular Indian dish succotash provides complete
protein, as does any combination of legumes and grains. These combinations
are referred to as complementary proteins. However, it is now Known that if
these is a mix of amino acids throughout the day, then having complementary
proteins at the same meal isn't necessary. Soybeans contain almost all of
the essential amino acids that make complete protein; they are also high in
calcium. Thus, strict vegetarians whose diets exclude all animal foods can
rely on tofu and other soy products for protein and some of their calcium.
NUTRITIONAL WINNERS
Legumes are among our most
nutritious plant foods -- high in protein, B-complex vitamins, iron,
potassium, and other minerals. They provide large amounts of fiber,
including the soluble type that is important in controlling blood
cholesterol levels. Studies have shown that people who eat more legumes have
a lower risk of heart disease.
Legumes contain a range of
important phytochemicals that have a number of disease-fighting properties.
Some of the important ones include: isoflavones, which are protective
against heart disease and cancer; saponins, which help lower cholesterol;
and phytosterols, which have anticancer and cholesterol-lowering properties.
Legumes are also a good food for
a diabetic diet because their balance of complex carbohydrates and protein
provides a slow, steady source of glucose instead of the sudden surge that
can occur after eating simple carbohydrates.
Most legumes are low in calories
and fat; soybeans and peanuts, however, are high in mostly unsaturated oils.
THE DOWNSIDE
Legumes harbor a number of toxic
substances or compounds that interfere with the action or absorption of
vitamins. Soybeans, for example, contain substances that interfere with the
absorption of beta carotene and vitamins B12 and D; beans and peas have an
anti-vitamin E compound. Heating and cooking inactivates most of these
substances, but to compensate for vitamin loss, balance legume consumption
with ample fresh fruits and yellow or dark green vegetables (for beta
carotene), lean meat or other animal products 9for vitamin B12), and cooked
greens, wheat germ, fortified cereals, seeds, nuts, and poultry (for vitamin
E).
People with gout are often
advised to forgo dried peas and beans, lentils, and other legumes because of
their high purine content. In susceptible people, purines increase levels of
uric acid and can precipitate and gout attack. some people of Mediterranean
or Asian descent carry a gene that makes them susceptible to favism, a
severe type of anemia contracted from eating fava beans. Anyone with a
family history of this disease must not eat this type of bean.
Some legumes, especially peanuts,
trigger an allergic reaction or migraine headaches in susceptible people. In
such cases the offending foods should be eliminated from the diet.
Dried beans, lentils, and peas
are notorious for causing intestinal gas and flatulence. The method of
preparation can help reduce gas production. Change the water several times
during the soaking and cooking process. (Lentils don't need to be soaked,
but rinsing them after cooking lowers their gas-forming potential.) Always
rinse canned beans and chickpeas; combining cooked legumes with an acidic
food may reduce gas production. Some herbs, especially lemon balm, fennel,
and caraway, can help to prevent flatulence.
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