Genistein may boost bone formation in older women
in bone mineral density in postmenopausal women, says a new
randomized, double-blind, placebo-controlled trial from Italy.
Previous studies have reported conflicting results concerning soy isoflavones (40 to 99 mg/d doses) and bone health for postmenopausal women.
The new study, using the 'gold-standard' clinical trial approach is an important addition to this on-going debate.
"Genistein decreased levels of bone resorption markers and increased levels of markers of new bone formation, producing a net gain in bone mass after one year and two years," wrote lead author Herbert Marini from Azienda Ospedaliera
Universitaria Policlinico "G. Martino", Messina.
Limiting bone loss could ease the burden of osteoporosis, estimated to affect about 75m people in Europe, the USA and Japan.
According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is €31.7bn in Europe, and 17.5bn in the US (2002 figure).
The total annual cost of osteoporosis in the UK alone is over £1.7bn (€2.5bn), equivalent to £5m (€7.3m) each day.
The researchers recruited 389 postmenopausal women (average age 54) with a bone mineral density (BMD) less than 0.795 grams per sq. cm at the top of the hip bone (femoral neck) and assigned them to an initial low-soy reduced fat diet for four weeks.
After this, they were randomly assigned to receive daily supplements of genistein (54 mg/d in 2 tablets, Laboratori Plants, Messina, Italy) or placebo for 24 months.
Both genistein and placebo tablets contained vitamin D (400 IU) and calcium carbonate (500 mg).
At the end of the study, Marini and co-workers found that BMD at the femoral neck had increased in genistein-supplemented group by an average of 0.035 g/cm2, and decreased by 0.037 g/cm2 in the placebo group.
Similar results were observed at the anteroposterior lumbar spine with a BMD increase of 0.049 g/cm2 for the genistein group, and a decrease of 0.053 g/cm2 in the placebo group.
Markers of bone resorption, pyridinoline and deoxypyridinoline in the urine, decreased as a result of genistein supplementation. "
This finding confirms that the positive effects of genistein on bone loss reduction are caused, at least in part, by a constant decrease in bone resorption," wrote the authors.
"This effect was time-dependent, suggesting that long-term intake produces ongoing effects on bone metabolism," they added.
However, the researchers do note that more of the participants in the genistein group experienced gastrointestinal side effects than the placebo study, and stopped their participation in the study (19 versus 8 per cent).
" We found that two years of treatment with genistein improved BMD and markers of bone turnover in a cohort of osteopenic postmenopausal women," wrote the authors.
"On the basis of these data, future studies in osteoporotic women are warranted to determine whether genistein also significantly decreases fracture risk in this group," they concluded.
Corresponding author Professor Francesco Squadrito told NutraIngredients.com that the group have a cohort of patients at three years and are planning to publish these additional results in a couple of months.
Source: Annals of Internal Medicine Volume 146, Pages 839-847 "Effects of the Phytoestrogen Genistein on Bone Metabolism in Osteopenic Postmenopausal Women" Authors: H. Marini, L. Minutoli, F. Polito, A. Bitto, D. Altavilla, M. Atteritano, A. Gaudio, S. Mazzaferro, A. Frisina, N. Frisina, C. Lubrano, M. Bonaiuto, R. D'Anna, M.L. Cannata, F. Corrado, E.B. Adamo, S. Wilson, and F. Squadrito
