UK researchers found that, when taken for a year, the supplements appeared to
curb spinal bone loss in women between the ages of 49 and 65.
Isoflavones are compounds found in soybeans, chickpeas and other legumes that
are similar to the female hormone estrogen. Because of this, researchers have
been studying whether soy protein or supplements containing isoflavones might
act as a sort of "natural" hormone replacement therapy.
Studies have shown that Asian women, whose traditional diet is rich in soy,
have a relatively low rate of hip fracture, as well as breast cancer and heart
disease. In addition, animal research has suggested that isoflavones might
lessen bone loss related to waning estrogen levels.
Some studies of women, however, have found no evidence of bone benefits, and
much of the research on isoflavones has involved only small groups of women
followed for a relatively short time.
The new study, which followed 177 women for a year, is one of the largest and
longest investigations of an isoflavone supplement to date, according to the
authors. They found that compared with women randomly assigned to take a
placebo, those who took a daily isoflavone tablet showed less bone loss in the
lower spine.
The findings are published in the American Journal of Clinical Nutrition. Novogen Ltd., maker of the isoflavone supplement
Promensil, provided the tablets and partial funding for the study.
Despite the study's positive results, it's too early to recommend isoflavone
supplements for fighting bone loss, study author Dr. Sheila Bingham, of the
Medical Research Council Dunn Human Nutrition Unit in Cambridge, told Reuters
Health.
For one thing, long-range studies are necessary to determine whether
isoflavones can cut the risk of bone fractures, a major cause of disability
among older adults.
Also unclear, Bingham noted, is whether a soy-rich diet might be more or less
beneficial than isoflavones supplements when it comes to bone health. The
supplement her team studied is derived from red clover.
The study involved women ages 49 to 65, most of whom were postmenopausal and
all of whom had recently had a mammogram to screen for breast cancer. Women with
a history of the disease were excluded.
At the end of the study, women in the supplement group had lost less bone
density in the lumbar spine than those in the placebo group had. There was no
clear difference between the groups as far as bone density in the hip, according
to the report.
To help ward off the bone-thinning disease osteoporosis, experts advise women
to get enough calcium and vitamin D, avoid smoking and exercise regularly
throughout their lives.
SOURCE: American Journal of Clinical Nutrition, February 2004.
