Miami Herald, FL
04-11-06
SOY: Nature's HRT?
A UM researcher wants to know if a plant can save women from bone loss
BY GEORGIA TASKER
gtasker@MiamiHerald.com
More and more women were coming into Dr. Silvinia Levis' office talking about
using soy as a substitute for hormone therapy.
''I'm not taking estrogen, I'm taking soy,'' patients would tell the Miami
endocrinologist. ``Do you think it will help?''
Levis, who specializes in women's health, didn't know the answer. ``So I
proposed we do a study.''
Levis' study -- to take place over the next five years -- will look at the long-term
consequences of taking phytoestrogens in preventing bone loss that occurs after
menopause. Phytoestrogens are plant-produced compounds contained in soy
that seem to mimic the hormone estrogen.
Bone loss -- which occurs when the ovaries no longer produce estrogen -- is one
of many consequences of menopause, a condition that has grown more
contentious in recent years. In 2002, the Women's Health Initiative, a
comprehensive, long-term women's medical study, found the use of estrogen
with progestin increases the risk of breast cancer and stroke, particularly in older
post-menopausal women. Those findings scared many women away from taking
hormone replacement therapy and left them with hot flashes, night sweats, bone
loss and other symptoms of menopause.
NATURAL PRODUCTS
''Many women are looking to natural products to relieve them of symptoms and
have none of the [health] risks of hormone replacement therapy,'' said Levis, a
professor in the University of Miami School of Medicine.
The study also will gather information on how phytoestrogens affect sleep, hot
flashes and general physical and emotional health.
Hormones are chemicals sent as signals from the body's transmitters such as the
pituitary gland, adrenal gland and the ovaries. They are sent to receptors on
cells, which then react in certain ways. Hormones from the ovaries are estrogens
that find receptors in the brain, liver, heart, uterus, breasts and bones. These
hormones do a number of things, such as increase endorphin levels, enhance
memory, strengthen bones and are essential for pregnancy.
Phytoestrogens (''phyto'' means plant) include compounds called isoflavones that
have estrogen-like activity. Beans are rich in these compounds, and soy is the
richest source.
Soy also produces protein. Some studies found that soy protein could lower LDL
or bad cholesterol. Since 1999, the Food and Drug Administration said foods
containing soy protein could be labeled as having the potential to reduce
cardiovascular heart disease. (Earlier this year, however, a 10-year study by the
American Heart Association cast doubt on soy's ability to significantly lower
cholesterol; the results were mixed on whether soy prevented postmenopausal
bone loss.)
Levis' study will look at purified soy isoflavones given in tablets to see whether
they prevent rapid bone loss that occurs in early menopause. Chemically, plant
estrogens don't attach strongly to human estrogen receptors in cells. But bones
are so receptive to phytoestrogens, it is possible a sufficient number of the
compounds could be retained to slow mineral loss that normally occurs with
menopause, says Dr. Carla Lupi, Miami gynecologist and consultant on Levis'
study,
''But just because you know something interacts with a receptor doesn't mean
you can conclude the outcome,'' Lupi said.
Patricia Murphy, food chemist and professor at Iowa State University who
has worked with isoflavones for 20 years, says researchers around the world are
looking at isoflavones and what they do.
Human estrogen can help prevent cancer, but also can promote cancer
development in the breast, prostate and colon. While the Chinese and Japanese,
who eat more soy than North Americans, have less cancer, no one knows
whether soy reduces the cancer rate or if it's something else.
''We don't know the dose range of phytoestrogens that can cause cancer,'' she
said.
Dr. Heidi Nelson, an internist and medical director of the Women's and Children's
Program at Providence Health System in Portland, Ore., was on the team of
physicians asked by the National Institutes of Health to review the medical
literature on menopause-related symptoms.
Many studies used inconsistent measures; many were too small, involving only
20 people and ending with a lot of drop-outs, or they used different formulations
of soy isoflavones.
''We don't have good support that [phytoestrogens from soy] help in any
measure,'' Nelson said. ``It may be that they don't work, or it may be that we
haven't studied them adequately yet. So we can't say no, but we can't say jump
on the bandwagon.''
RECRUITING VOLUNTEERS
In the University of Miami's SPARE study (Soy Phytoestrogens as Replacement
Estrogen), the plan is to rotate women through for two years at a time. Levis is
recruiting 300 female volunteers, ages 45 to 58. Each will receive a free yearly
mammogram, bone density test and measurements of hormone levels. Groups of
women will partake in the study for two years, with some beginning as others are
ending.
''Studies can be full of surprises,'' said Levis. ``There is a lot of small evidence
that phytoestrogens might work, but the evidence isn't strong. In Asian
populations, those women who eat a lot of soy every day, bone loss is less.''
As to what course of action menopausal women should adopt now, Lupi doesn't
have a one-size-fits-all answer.
``If your quality of life is impaired by the symptoms, then take estrogen,
understanding there are small risks on the statistical level. Assuming you are a
healthy person, find the lowest effective dose.
''There are no guidelines on how long to stay on or go off,'' she said. ``It depends
on how a patient perceives risk. Some women are nervous and are likely to go
off therapy earlier than others.''