Citrus Flavanones and Bone Health

Abstract

Flavanones are a class of fl avonoids found mainly in citrus fruits, the most common ones being hesperidin and naringin. These compounds exist as glycoside conjugates in the fruits at relatively abundant concentrations. Despite the extensive metabolism, the fl avanones circulate in blood in the low m M range, which we therefore consider as the “physiological” concentration as opposed to more pharmacological concentrations (50–100 m M) often used in cell culture studies. Among the various biological effects attributed to the fl avanones, the more consistent ones are anti-in fl ammatory and lipid-lowering properties. In particular, the anti-in fl ammatory effects of the fl avanones have been shown to be mediated through the inhibition of the NF- k B pathway. Concerning the effects of fl avanones on bone metabolism, the in vivo evidence in preclinical studies mimicking postmenopausal or senile bone loss shows an effect of hesperidin on preservation of bone mineral density (BMD) associated with reduced collagen breakdown. In the fi rst placebo- controlled, randomized, double-blind clinical trial to be performed on the ability of hesperidin (500 mg daily for 2 years) to attenuate bone loss in postmenopausal women, we found that hesperidin did not signi fi cantly alter the 1–2 % BMD loss/year generally observed in this population. However, the subjects consuming hesperidin presented a better balance in bone metabolism as re fl ected by the bone turnover index. Any nutritional approach to bone health should include the main bone micronutrients (calcium, vitamin D) already shown to improve BMD in osteopenic situations. However, further bioactive nutrients in the diet, such as the fl avanones, may play a further role in modulating bone turnover and help protect against bone loss in at-risk populations. The question remains as to how best to measure such effects and show their relevance to bone quality, whether it is via bone biomarkers, bone architecture, or bone mineral density in combination or not with calcium and vitamin D.