Do Soy Foods Cause Cancer?

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Do Soy Foods Cause Cancer?

JoAnn Guest

Nov 12, 2006 18:08 PST

 

 

What's the latest on the soy-breast cancer connection? I just heard

a report about a newly discovered link.

 

Researchers at the University of Illinois at Urbana-Champaign

recently announced results of research suggesting that the " highly

purified " soy foods and soy supplements marketed in the United

States may promote the growth of some pre-existing breast cancers.

The study results, to be published in a future issue of the journal

Carcinogenesis, showed that breast tumors in mice grew when the

animals were fed highly processed soy products missing some of the

natural components of whole soybeans.

 

In the study, scientists used products that contained the soy

isoflavone genestein in various stages of isolated purity. Breast

tumors

neither grew nor regressed when the mice were fed foods containing

minimally processed soy flour.

 

Whole soy foods, such as tofu, tempeh, edamame and miso - much used

in

Asian diets - are protective.

 

A little background may help to explain the potential relevance of

these

findings. First of all, rates of breast cancer in Asia are much

lower

than they are in the U.S., and this difference may be related to the

fact that Asian women eat much more soy than Western women.

 

The compounds in soy that may make the difference are isoflavones,

which

are biologically active with phytoestrogenic (plant estrogen)

effects.

 

These hormones are weaker than the estrogens produced in women's

bodies

and those from such external sources as meats and dairy products

from

" hormone-fed " animals, as well as artificial chemicals

and " industrial

pollutants " (zenoestrogens) that act as estrogen.

 

As far as the new findings about soy and breast cancer are

concerned,

take note that the mice had pre-existing cancer.

 

The highly processed soy foods didn't cause the cancer to appear but

did

promote its growth. A few previous studies have shown that certain

isoflavone products act selectively, influencing the mechanisms in

the

body that cause symptoms such as hot flashes, while not showing

effects

on breast or uterine tissue.

 

The study director, William G. Helferich, a professor of food

science

and human nutrition, said that his study results suggest

that " highly

processed " isoflavone-containing products may pose a risk to

postmenopausal women who are consuming them as an alternative to

hormone

replacement therapy.

 

Until further research answers the question of safety with long-term

use, I recommend that you avoid soy supplements entirely. However, I

still recommend one to two servings a day of whole soy foods. A

serving

is a cup of soy milk or one half-cup of tofu, tempeh, edamame or soy

nuts. At those amounts you'll get the benefits of soy without the

theoretical risks of taking in too many isoflavones.

 

Andrew Weil, M.D.

www.drweil.com

 

 

JoAnn Guest

mrsjo-

www.geocities.com/mrsjoguest/Diets