LEE BOWMAN, "Soy shouldn't increase cancer risk, study finds", Scripps
Howard News Service , January 15, 2006,
Link:
http://www.shns.com/shns/g_index2.cfm?action=detail&pk=SOY-CANCER-01-15-06

The possible role of plant estrogens from soy products in stimulating
breast cancer cells has rumbled through the research community and
health foods industry for several years.

There's been a mixed bag of study results from mice and humans. One
report showed that soy proteins promoted breast cancer in mice lacking
ovaries, and thus not producing much estrogen on their own. Another
study on mice with ovaries intact found that soy inhibited tumor
growth.

And human population studies have found that women who consumed diets
high in soy generally have lower rates of breast cancer.

A study published Sunday in the journal Cancer Research may not settle
the soy question for all women. But based on a complex test involving
monkeys, it suggests that plant estrogens should not increase the risk
of breast cancer in postmenopausal women, and may provide some
protection to some women taking estrogen supplements.

"Even at high doses, we found no evidence that the estrogen-like
compounds in soy, called isoflavones, stimulate cell growth or other
markers for cancer risk in breast tissue,'' said Charles Wood, a
veterinarian researcher at Wake Forest University Baptist Medical
Center and lead author of the study.

"The study also suggests that women who have higher levels of estrogen
may actually gain a protective effect from higher doses of soy
isoflavones,'' he added.

Wood and his colleagues evaluated the soy proteins' effect in the
presence of different levels of estrogen by rotating 31 postmenopausal
cynomolgus monkeys through eight different diets. Each diet contained
one of four different isoflavone doses along with either a low or high
dose of estrogen.

The isoflavone doses were equivalent to these human levels: no
isoflavones, 60 milligrams (the typical Asian diet), 120 milligrams
(the highest level that can be achieved through diet alone) and 240
milligrams (levels obtained through supplements).

Estrogen doses were designed to mimic either a low or high-estrogen
environment found in postmenopausal women. Those levels can vary
depending on a women's amount of body fat, which produces estrogen, and
whether they are taking hormone replacement therapy.

The researchers found that in the low-estrogen environment, there was
no evidence of increased breast cell proliferation or other markers of
breast cancer risk at any level of isoflavone exposure, even at doses
several times higher than the typical Asian diet.

In a high estrogen environment, there was higher breast cell
proliferation both when isoflavones weren't in the diet and when they
were present in lower doses. However, the addition of high levels of
soy isoflavones tended to block estrogen effects in breast tissue.

"For women at increased risk of breast cancer due to higher estrogen
levels, a diet high in soy isoflavones may offer a modest breast
protective effect,'' said Wood.

But he cautioned that the study may not apply to women who have not
gone through menopause and thus have higher and more dynamic hormone
levels, or to women who are taking combined hormone therapy with
estrogen and progestin.

On the Net: http://www.cancerres.aacrjournals.org/

www.wfubmc.edu