Abstract
Here, we examined the preventive effect of Hyuganatsu orange juice (Citrus tamurana Hort. ex Tanaka) on osteoporosis in postmenopausal women and evaluated whether the underlying mechanism involves altered calcium absorption in the intestinal tract. Twenty-five postmenopausal healthy women aged 59–64 years were randomly divided into two groups: the control and Hyuganatsu groups. The treatment group consumed Hyuganatsu orange juice daily for 3 months. As a result, decreases in serum levels of intact procollagen type I N-propeptide (IPINP), a parameter of bone formation, and tartrate-resistant acid phosphatase 5b (TRAP5b), a parameter of bone resorption, were observed. No statistically significant differences were observed between the two groups with respect to other serum parameters used for clinical evaluation of osteoporosis and liver function. In addition, we measured the rate of intestinal calcium absorption, a major determinant, using everted sacs of rat intestine in vitro, and found that the addition of active components such as water extract (WE) and WE-ultrafiltration (WEU) of Hyuganatsu orange juice to the incubation medium led to a marked increase in the absorption of calcium in the intestinal tract. We also observed that arabinogalactan was the active component of Hyuganatsu orange juice. Together, our results suggest that Hyuganatsu orange is a useful citrus fruit and that daily drinking of juice may be effective in preventing osteoporosis in postmenopausal women.
