Eicosapentaenoic acid inhibits bone loss due to ovariectomy in rats

Eicosapentaenoic acid (EPA), one of the polyunsaturated fatty acids, is well-known to have a wide variety of beneficial biological functions. In the present work we demonstrate another new beneficial effect of EPA on bone metabolism in vivo. Ovariectomized rats were divided into 4 groups under the same calorie intake condition; (1) normal diet, (2) low calcium diet (1.5 mg/day), (3) EPA-enriched diet (160 mg/day/kg), (4) EPA-enriched and low calcium diet. These diets were continued for 35 consecutive days. The bone weight of the femora and tibiae decreased significantly in the low calcium group, but the decrease was inhibited in the EPA-low calcium group. Moreover, in the rupture test, which indicates bone strength, the femora in the low calcium group were easier to break than in the normal calcium diet groups. In the EPA-low calcium group the strength of the bone was equivalent to that in the normal diet group. These results suggest that an EPA-enriched diet prevents the loss of bone weight and strength caused by oestrogen deficiency or inadequate nutrition. There is a possibility that EPA could be developed to be a novel anti-osteoporosis drug.