FAQ Genistein
Q: What is Genistein?
A: Genistein (or aglycone genistein) is an isoflavone phytoestrogen that is abundant in certain fermented soy products (i.e. natto, miso, tempeh), and has been shown to increase bone mineral density in osteopenic postmenopausal women.
Q: Have any studies been done on genistein?
A: A study was recently published in the journal The Annals of Internal Medicine. University Hospital in Messina, Italy conducted a randomized placebo-controlled trial of 389 women aged 49 to 67 to examine the effects of 2 years' treatment with genistein on bone mineral density and bone metabolism in postmenopausal women with osteopenia. Researchers concluded that genistein increased bone mineral density at the femoral neck and lumbar spine at 24 months.
Q: How much Genistein did these women take?
A: The Messina study concluded that 54 mg genistein per day, taken in divided doses irregardless of meals, increased bone mineral density in postmenopausal osteopenic women.
Q: I eat soy. Can I get enough genistein from my diet?
A: The amount of genistein (54 mg/day) administered in this study cannot be easily obtained by a mere change of diet. Given the low amounts of aglycone genistein in most soy foods as well as supplements and low consumption of fermented soy products in the western diet, it would be extremely difficult to obtain 54 mg/day of purified genistein from food sources. Moreover, soy, soy supplements and soy food products also typically contain high levels of diadzein, which may antagonize the effects of genistein on bone. For instance, individuals would need to consume over 1 kg of the highest genistein containing foods (i.e. about 4 kg of tofu or 9 kg of soymilk) to achieve the amount of genistein aglycone (54 mg/day) administered in this study.
Q: I take estrogen HRT to help with bone mineral density. Would genistein benefit me?
A: HRT treatment of osteopenia is associated with increased risk for breast, endometrial and ovarian cancer, cardiovascular disease, and stroke. However, as a natural selective estrogen receptor (ER) modulator, genestein may positively regulate bone cell metabolism without the harmful estrogenic activity in the breast and uterus. Genistein produces effects on osteoblasts that inhibit osteoclastic activity, promotes osteoblast survival and causes direct stimulation on the anabolic effects of osteoblasts.
Q: Can I give genestein to my patients with osteoporosis?
A: Future studies in osteoporotic women are warranted to determine whether genistein also significantly decreases fracture risk in this group.
Q: Is genistein contraindicated for any patient population?
A: Genistein is not intended for pediatric patients or for pregnant or nursing women because it has not been tested in these groups. Moreover, because no studies have been done in these populations, as a precaution, aglycone genistein is contraindicated for patients with a history of cancer of the breast or reproductive organs.
©Labrix ETL/LF 2008
Article Synopsis:"Effects of the Phytoestrogen Genistein on Bone Metabolism in Osteopenic Postmenopausal Women: A Randomized Trial." Ann Intern Med, 2007; 146(12):839-47. 45456 (9/2008).
Bone mineral density (BMD) is reduced with the onset of menopause. HRT has been the hallmark treatment of osteopenia for many years, but it is associated with an increased risk of breast, endometrial, and ovarian cancer, cardiovascular disease, and stroke. Phytoestrogens, present in soy products, carry lower risk for such adverse effects and are used by many women to maintain BMD. Genistein (aglycone genistein), an isoflavone phytoestrogen that is abundant in certain fermented soy products (natto, miso, tempeh), has been shown in postmenopausal women to increase BMD at the lumbar spine and femoral neck with no adverse effects.
A recent study conducted at the University Hospital in Messina, Italy set out to explore the effects of genistein. This was a randomized placebo-controlled trial of 389 women aged 49 to 67 to examine the effects of 2 years' treatment with genistein on BMD and bone metabolism in postmenopausal women with osteopenia. Researchers concluded that genistein increased bone mineral density at the femoral neck and lumbar spine at 24 months.
Included were 389 women aged 49 to 67 years who had been postmenopausal for at least 12 months and were in good general health. Excluded were women with systemic diseases, those using hormone therapy or steroids, smokers, those with family history of estrogen-dependent cancer, and those with BMD at the femoral neck greater than 0.795 g/cm2 corresponding to a T score of -1.0 SD (i.e. osteoporosis).
After 4 weeks of stabilization with a low-soy, reduced-fat diet, women were assigned to receive either 54 mg/day of genistein in 2 tablets or identical placebo. Both genistein and placebo tablets contained calcium carbonate (500 mg) and vitamin D (400 IU). All participants were counseled to eat a reduced fat diet. The intake of soy, legumes, or other supplements was prohibited.
The primary outcome was BMD at the anteroposterior lumbar spine and femoral neck at 12 and 24 months. Secondary outcomes were serum levels of bone-specific alkaline phosphatase
and insulin-like growth factor I, and urinary excretion of pyridinoline and deoxypyridinoline. Data on adverse events including changes in endometrial thickness were also collected.
After 24 months, Mean BMD at the femoral neck increased from 0.667 g/cm2 at baseline to 0.683 g/cm2 at 1 year and 0.702 g/cm2 at 2 years in genistein recipients. Mean BMD decreased from baseline to years 1 and 2 in placebo recipients. Similarly, mean lumbar spine BMD during 2 years increased in the genistein group and decreased in the placebo group. Genistein statistically significantly decreased urinary excretion of pyridinoline and deoxypyridinoline, increased levels of bone-specific alkaline phosphatase and insulin-like growth factor I, and did not change endometrial thickness compared with placebo. Biochemical and liver function did not change
with time. At 2 years, genistein use was associated with reduction in the mean number of hot flashes per day vs placebo (1.7 vs 3.9 per day). More genistein recipients than placebo recipients experienced gastrointestinal side effects (19% vs. 8%; P = 0.002) and discontinued participating in the study.
Conclusion: Twenty-four months of treatment with genistein has positive effects on BMD in osteopenic postmenopausal women.
©Labrix ETL/LF 2008
