Soy fails to prevent menopausal bone loss over 2-year trial
MedWire News: Soy isolfavones were ineffective at preventing postmenopausal bone loss and menopausal symptoms , show results from a 2-year trial.
A reduced prevalence of osteoporotic fractures in Asian women has been attributed to their soy-rich diet and, in light of this, trials have tested for various effects of isoflavones derived from soy protein. Most have been limited by factors such as short duration, low isoflavone dose, few participants, and wide age and menopausal status.
The Soy Phytoestrogens As Replacement Estrogen (SPARE) study, whose results are now published in the Archives of Internal Medicine, addressed the lack of existing evidence.
The study included 248 menopausal women between 45 and 60 years of age without osteoporotic fractures, a bone mineral density (BMD) score above -2.0, and a body mass index (BMI) below 32 kg/m2. The women had no recent cancer and were not taking bone active drugs or supplements.
The participants were randomly assigned to receive either isoflavone tablets 200 mg/day or placebo for 2 years. In all, 182 women completed the study. No significant differences were found between the soy-treated patients and the placebo-treated patients regarding changes in spinal (-2.0 vs -2.3%), total hip (-1.2 vs -1.4%), or femoral neck (-2.2 vs -2.1%) BMD measured using dual-energy X-ray absorptiometry .
Hot flashes were significantly more frequent in the patients given the soy tablets compared with those given placebo (48.4 vs 31.7%), but no significant differences were found for any other menopausal symptoms or vaginal cytologic characteristics.
Soy was associated with a significantly increased risk for constipation compared with placebo (31.2 vs 20.6%).
"Because of concerns regarding the risk of estrogens, a need exists for alternative interventions that could provide the beneficial effects of estrogens without the adverse effects on breast or cardiovascular health," write Silvia Levis (University of Miami, Florida, USA) and colleagues.
They conclude, however, that as soy isoflavones do not prevent bone loss or menopausal symptoms, there is no evidence to suggest soy is an adequate alternative to estrogens.
In an accompanying commentary, Deborah Grady (University of California, San Francisco, USA) said the search for an alternative is limited by a lack of knowledge about the mechanisms behind hot flashes and night sweats.
Noting that it is symptoms such as these that prompt women to seek therapy, and the degree of symptom relief they experience is what matters most to patients, she wrote: "Perhaps efforts should be directed away from a one-size-fits all therapy for menopausal symptoms toward using existing treatments to target the symptoms that disturb patients the most."
By Chloe McIvor