New research indicates that soybeans and soy-based
foods, a staple in the diets of many health-conscious consumers, may
promote kidney stones in those prone to the painful condition.
The researchers measured nearly a dozen varieties of
soybeans for oxalate, a compound that can
bind with calcium in the kidney to form kidney stones.
They also tested 13 types of soy-based foods, finding
enough oxalate in each to potentially cause problems for people with a
history of kidney stones, according to Linda Massey, Ph.D., at Washington
State University in Spokane.
The amount of oxalate in the commercial products
easily eclipsed the American Dietetic Association's 10
milligram-per-serving recommendation for patients with kidney stones, with
some foods reaching up to 50 times higher than the suggested limit, she
"Under these guidelines, no soybean or soy-[based]
food tested could be recommended for consumption by patients with a
personal history of kidney stones," she said.
No one had previously examined soy foods for oxalate,
thus the researchers are the first to identify oxalate in store-bought
products like tofu, soy cheese and soy drinks. Other foods, such as
spinach and rhubarb, also contain significant oxalate levels, but are not
as widely consumed for their presumed health benefits, Massey said.
During their testing, the researchers found the
highest oxalate levels in textured soy
protein, which contains up to 638 milligrams of oxalate per
Soy cheese had the lowest oxalate content, at 16
milligrams per serving. Spinach, measured during previous research, has
approximately 543 milligrams per one-cup (2 oz. fresh) serving.
Soy, a natural source of protein, fiber and healthy
oils, is used to enhance a myriad of foods, ranging from hamburgers to ice
cream. It can be ground into flour and used in a variety of grain
products, or formed into chunks and ground like meat.
Soy is also being studied for its potential to lower
cholesterol, reduce bone loss and prevent breast cancer. The U.S. Food and
Drug Administration recently approved a new label on foods containing at
least 6.25 grams of soy protein per serving that boasts of a reduced risk
of cardiovascular disease.
Oxalate, however, cannot be metabolized by the body
and is excreted only through urine, Massey said. The compound has no
nutritional value, but binds to calcium to form a mass (kidney stones)
that can block the urinary system, she said.
Further research is needed to find types of soybeans
with less oxalate, or to develop a processing method to remove the
compound before it reaches consumers, she added.
No one knows precisely why kidney stones occur in
But Massey said high
levels of oxalate in the urine increase the risk and those with a family
history of the ailment are more likely to suffer from the
condition; individuals with a low probability of kidney stones are
unlikely to be affected by oxalate in soy-based foods.
More than one million people were diagnosed with
kidney stones in the United States in 1996, the most recent available
data, according to the National Institutes of Health.
Stones can range in size from the diameter of a grain
of rice to the width of a golf ball. An estimated 10 percent of the U.S.
population, mostly men, will develop a kidney stone at some point in their
lives, according to the NIH.
Agricultural and Food Chemistry September 2001
Dr. Mercola's Comment:
Yet one more nail in the coffin of non-fermented
soy which I do not believe is designed to be eaten. This study suggests
that the over one million patients with kidney stones should not consume
If you are still brainwashed by the edible oil
industry's incredibly effective media spin on soy, then please review the
soy index page link below which has hundreds of pages describing the
reason's you will not want to regularly consume non-fermented soy
Soy protein powders and soy formula are the worst
offenders and I don't believe that they should be consumed by
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