Background and purpose: Osteoporosis is a silent disease which is causing death of significant population due to bone fractures. Use of natural supplements is considered with respect to side effects of chemical drugs. In this study, the effect of sargassum algae on osteoporosis disease was investigated.

Method: The study was done on 80 mice heads of NMRI race. After osteoporosis induction, the mice divided into the control, sham, positive control, experimental and negative control groups. The therapeutic dose of positive control group was 125 mg/kg/day of calcium and 0.025 μg / week / mice vitamin D and that of in the experimental group was 10mg/100g(bw)/day Sargassum algae extract that was fed for 28 days to each group. Finally, histopathology sections were studied.

Findings: The negative control group had more degradation in lamellar bone (bone blades) than other groups (P<0.01). The experimental group had less degradation compared to negative control group and also, the number of observed osteoblasts in the periosteum had a significant increase than negative control group. (P<0.01)

Result and discussion: Our study showed that Sargassum tenerrimum algae has meaningful effect on osteoporosis and since includes active ingredients with absorbable calcium; it can have the ability of osteoporosis inhibition from several ways. Also, it was shown that algae has unique effect in ossification process and inhibition of osteoclast production via activation of Smad and BMP path, RANK protein inhibition and TNFα.