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Soy-Based
Products May Increase UTI
Excerpt
By Colette Bouchez, HealthScoutNews
(HealthScoutNews)
--Got kidney stones? Don't drink soy milk or eat tofu, soy energy
bars or just about anything else containing the otherwise healthful
soybean. New research shows soy-based products could increase
the risk of developing this painful urinary tract condition.
The culprit
is oxalate, a compound in plants that recently was discovered
to be abundant in the soybean.
"We have
long known that legumes are high in oxalate and that oxalate can
increase the risk of kidney stones. … Now we know that soybeans,
a legume, and foods made from soy are also high in oxalate, with
levels far above what is recommended for those who suffer with
kidney stones," says study author Linda K. Massey, professor
of human nutrition at University of Washington at Spokane.
Indeed, while
the American Dietetic Association (ADA) suggests that patients
with calcium oxalate kidney stones limit oxalate levels to no
more than 10 milligrams per serving, Massey found soy products
can have more than 50 times that amount. Texturized soy protein
alone weighs in at a whopping 638 milligrams of oxalate per average
serving of almost 3 ounces. Soy cheese, with 16 mg of oxalate
per serving, still is considered high.
"Under
the current guidelines, there isn't a single soy-based food that
would be appropriate for people who suffer with any condition
for which oxalate represents a problem," says Massey.
Other high-oxalate
foods include legumes like refried beans, lentils and peanuts,
each containing between 100 and 200 milligrams of oxalate per
serving. The only food other than soy that far exceeds the suggested
ADA oxalate levels is spinach, with 548 milligrams per 2-ounce
serving.
For most folks
oxalate, which has no nutritive value of its own, is not a problem.
Massey says healthy people usually pass it from their body in
urine with no consequence.
For some,
however, oxalate combines in the body with calcium to form the
hard mass of a kidney stone that can painfully block the urinary
system. The stones sometimes pass on their own, but many times
require surgery to provide relief.
While no one
is certain why some of us get kidney stones while others do not,
for those who do, "Oxalate can be a factor that increases
that risk," says Massey.
Other nutritionist
agree but say the cautions about soy apply only to those who are
oxalate sensitive and not the general population.
"If you
do not have this problem, don't be afraid to eat soy. It is a
healthy, non-animal source of protein that is low in fat and rich
in fiber, and it is a healthy food for most people," says
Barrie Wolfe, a dietician and nutritionist at New York University
Medical Center.
In addition
to affecting stone formation, other research has shown that high
oxalate foods can irritate a chronic gynecological condition called
vulvar vestibulitis, a problem marked by extreme vulvar pain during
intercourse, and sometimes even when walking or sitting.
Massey's
discovery about soy products also may be significant for women
just before menopause, when the risk of vulvar pain increases
and when many women turn to soy-based products for hormonal support.
"We plan
to study isoflavones, a component of soy often found in many menopause-related
products, to check oxalate levels here as well," says Massey.
Massey's study
analyzed and measured oxalate in a dozen varieties of soybeans
and 13 different types of soy-based foods, including tofu, soy
cheese and soy drinks.
Eleven of
the soybean varieties contained significantly high levels of oxalate,
as did all the soy-based food products.
In addition,
the study showed that converting soy beans into various food forms
does not alter oxalate levels. "They remain high regardless
of cooking or other processing," says Massey.
The age of
the soy products also didn't seem to matter. Levels in texturized
soy protein, for example, were nearly identical in batches purchased
nearly three years apart.
The study
appears in the September issue of the Journal of Agricultural
and Food Chemistry, a publication of The American Chemical
Society.
What To
Do
For Massey
the message is clear: "If you suffer from any oxalate related
condition, don't eat soy-based foods."
For Wolfe,
the take-home message is that variety is not only the spice of
life, it's also the basis of a healthy diet.
"Balance
and variety of all food groups is key. You don't want to have
an excess of any one food in your diet, no matter how healthy
a food it is, and you don't want to focus on only one food, even
a food as healthy as soy," says Wolfe.
To learn more
about the oxalate content of foods, click
here or
here.
For information
on the health benefits of soy, click
here.
Reference
Source 101
For more information on how to prevent other diseases, use
PreventDisease.com's "Quick
Prevention Resources".
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