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the vegetarian starter kit
In the past, some people believed one could
never get too much protein. In the early 1900s, Americans were
told to eat well over 100 grams of protein a day. And as
recently as the 1950s, health-conscious people were encouraged
to boost their protein intake. Today, some fad diet books
encourage high-protein intake for weight loss, though
Americans tend to take in twice the amount of protein they
need anyway. And while individuals following such a diet have
had short-term success in losing weight, they are often
unaware of the health risks associated with a high-protein
diet. Excess protein has been linked with osteoporosis, kidney
disease, calcium stones in the urinary tract, and some cancers.
The Building Blocks of Life
People build the proteins of their bodies
from amino acids, which, in turn, come from the proteins they
eat. A varied diet of beans, lentils, grains, and vegetables
contains all of the essential amino acids. It was once thought
that various plant foods had to be eaten together to get their
full protein value, but current research suggests this is not
the case. Many nutrition authorities, including the American
Dietetic Association, believe protein needs can easily be met
by consuming a wide variety of amino acid sources over an
entire day. Also, eating enough calories is essential for the
best use of protein by the body.
The Trouble with Too Much Protein
The average American diet contains meat
and dairy products. As a result, it is too high in protein.
This can lead to a number of serious health problems:
Kidney Disease: When people eat too much
protein, they take in more nitrogen than they need. This
places a strain on the kidneys which must expel the extra
nitrogen through urine. People with kidney disease are
encouraged to eat low-protein diets. Such a diet reduces
the excess levels of nitrogen, and can help prevent kidney
Cancer: Although fat is the dietary
substance most often singled out for increasing oneีs
risk for cancer, protein also plays a role. Populations
that eat meat regularly are at an increased risk for colon
cancer, and researchers believe that the fat, protein,
natural carcinogens, and the absence of fiber in meat all
play roles. In 1982, the National Research Council noted a
link between cancer and protein.
Osteoporosis and Kidney Stones: Diets
that are rich in protein, especially animal protein, are
known to cause people to excrete more calcium than normal
through their urine and increase the risk of osteoporosis.
Countries with lower-protein diets have lower rates of
osteoporosis and hip fractures.
Increased calcium excretion increases
risk for kidney stones. Researchers in England found that
by adding about 5 ounces of fish (about 34 grams of
protein) to a normal diet, the risk of forming urinary
tract stones increased by as much as 250 percent.
For a long time it was thought that athletes needed much
more protein than other people. The truth is that athletes
need only slightly more protein, which is easily obtained in
the larger servings athletes require for their higher caloric
intake. Vegetarian diets are great for athletes. To consume a
diet that contains enough, but not too much, protein, simply
replace animal products with grains, vegetables, legumes (peas,
beans, and lentils), and fruits. As long as one is eating a
variety of plant foods in sufficient quantity to maintain oneีs
weight, the body gets plenty of protein.
1. Position of American Dietetic Association: Vegetarian Diets. J Am Diet Assoc 1988;88:351-5.
2. El Nahas AM, Coles GA. Dietary treatment of chronic renal failure: ten unanswered questions. Lancet 15 March 1986:597-600.
3. Pellet PL. Protein requirements in humans. Am J Clin Nutr 1990;51:723-37.
4. Committee on Diet, Nutrition, and Cancer of the National Research Council. Diet, Nutrition, and Cancer. Washington, DC, 1982.
5. Zemel MB. Calcium utilization: effect of varying level and source of dietary protein. Am J Clin Nutr 1988;48:880-3.
6. Sherman HC. Calcium requirement in man. J Biol Chem 1920;44:21.
7. Hegsted DM. Calcium and osteoporosis. J Nutr 1986;116:2316-9.
8. Robertson WG, Heyburn PJ, Peacock M, Hanes FA, Swaminathan R. The effect of high animal protein intake on the risk of calcium stone-formation in the urinary tract. Clin Sci 1979;57:285-8.