Summary: Safety, Efficacy, and Optimal Dosage of Soy Isoflavones to Prevent
The use of over-the-counter soy isoflavone supplement is
becoming common among postmenopausal women for the
prevention of osteoporosis. Preliminary studies have indicated that soy isoflavones
can prevent osteoporosis and can reduce the symptoms of menopause. However,
there is no scientific evidence to document its long-term safety and efficacy
in preventing osteoporosis.
The primary goal of the $4.5 million project named Osteoporosis Prevention
Using Soy or OPUS is to determine whether isoflavones work, whether they are
safe over the long term and the optimal dosage. The secondary goal is to communicate
the study findings in easily understandable terms to both healthcare providers
Four hundred healthy, postmenopausal women will be enrolled at three U.S.
sites in a two-year follow-up, randomized, double-blind, placebo-controlled
study. One-third of the women will receive a placebo, one-third will receive
isoflavone supplementation at 80 mg/day, and the remaining one-third will
receive isoflavone supplementation at 120 mg/day.
To monitor safety, mammograms, well-woman examinations, Pap smears, stool
guaiac tests, and clinical blood chemistries will be performed. To monitor
efficacy, total body and regional bone mineral content and density, as well
as biochemical bone markers will be measured. To determine optimal dosage,
changes in bone measurements will be related to blood isoflavone concentrations.
Industrial partners include Acatris Holding B.V., who provided the SoyLife
isoflavone materials; EB Healthpharma B.V., who manufactured and packaged
the placebo and isoflavone tablets; Swanson Health Product, who provided the
multivitamin supplement; and Source Naturals who provided the calcium supplement.
The multi-state, multi-institutional investigation ensures that the study
results are representative of postmenopausal women in the U.S. population.
Raising awareness of osteoporosis and translating and disseminating the scientific
findings to healthcare providers and consumers will improve knowledge of how
to prevent this common, costly, debilitating disease.