A composition comprises soy isoflavones (a1) and viable lactic acid bacteria (b1). ACTIVITY : Gynecological; Osteopathic. 95 Days old Sprague-Dawley rats were ovariectomised under equitesin anesthesia 3 ml/kg body weight intraperitoneally. The animals were divided into 4 groups of 8 animals each. A 5th group of 8 animals was sham operated and kept as non-ovariectomised controls. The rats had free access to water and were fed ad libitum. Soy isoflavones (SIs) and Lactobacillus sporogenes (Ls) were suspended in 0.5% hydroxy-propyl-methyl- cellulose in water (vehicle), and daily administered with gastric tube in a dose of 10 ml/kg body weight. The groups were treated as follows. Group 1: Sham operated, non- ovariectomised controls: vehicle; Group 2: Ovariectomised controls: vehicle; Group 3: Ovariectomised treated with SIs: genistin 0.5 mg/kg body weight + daidzin 0.5 mg/kg body weight; Group 4: Ovariectomised treated with SIs + Ls: genistin 0.5 mg/kg body weight + daidzin 0.5 mg/kg body weight + 8 million per kg body weight spores of Ls; and Group 5: Ovariectomised treated with SIs+Ls+ Equisetum: genistin 0.5 mg/kg body weight + daidzin 0.5 mg/kg body weight + 8 million per kg body weight spores of Ls+ 1.5 mg/kg body weight Horsetail shoots dry extract (standardized in 7% silicon). Six weeks after ovariectomy, the rats were killed. The uteri were extracted an immediately weighed, the femurs were freed from the soft tissues, their length was measured, volume and density were measured, then they were ashed for 24 hours at 640[deg]C. Each ash sample was weighed and dissolved in 6 N HCl. Calcium was measured in the resulting solution. The results obtained at the end of the study were: six weeks after ovariectomy there was no significant change of body weight in any of the ovariectomised animal groups versus Group 1; in Group 2 there was a very significant decrease of the weight of uterus and a significant decrease in the length, density, ash weight, calcium and phosphorus content of the femurs, showing the negative effects of the oestrogen deficiency on bone trophism; Group 3 had no significant effects on body weight and on uterus (absence of stimulation of alpha oestrogen receptors, but increased significantly the femoral length and the bone phosphorus, showing a moderate positive effect on bone trophism; Group 4 notably and surprisingly improved bone trophism, as shown by the significant increase of all bone trophism markers (femur length, density, ash weight, calcium and phosphorus content), supporting the rationale of the SIs-Ls combination to enhance the positive effects of the SIs on bone by favoring the bioavailability of the SIs; Group 5 elicited a further unexpected improvement in all bone trophism markers (femur length, density, ash weight, calcium and phosphorus content), confirming the anabolic effects of this natural herbal product on the bone. In conclusion, Ls remarkably strengthened the anabolic effects of SIs on the bone, due to the enhancement of the bioavailability of SIs and to the enhancement of intestinal calcium and phosphorus absorption elicited by the probiotic properties of Ls. The addition of Horsetail extract promoted a further beneficial effect of bone anabolism. Notably, neither SIs nor SIs+Ls, had significant effects on the weight of uterus, showing the absence of the stimulation of the alpha oestrogen receptors. MECHANISM OF ACTION : None given.