Quercetin, fruit consumption, and bone mineral density

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Dear Sir:

McGartland et al (1) reported a correlation between a diet high in fruit and bone mineral density. Their article includes a discussion of how a low pH stimulates osteoclasts and how fruit's alkaline-forming properties influence the body's acid-base balance.

Another mechanism exists that could work in parallel or in synergy with the one proposed by McGartland et al. Diets high in fruit contain high amounts of flavonoids (2). The flavonoid quercetin decreases the differentiation of osteoclast progenitor cells and inhibits the activity of mature osteoclasts (3–5). Quercetin might act together with the alkaline-forming properties of fruit to inhibit osteoclasts and enhance bone mineral density.

ACKNOWLEDGMENTS

The author had no conflicts of interest to report.

REFERENCES

1. McGartland CP, Robson PJ, Murray LJ, et al. Fruit and vegetable consumption and bone mineral density: the Northern Ireland Young Hearts Project. Am J Clin Nutr 2004;80:1019–23.
2. Boyer J, Liu RH. Apple phytochemicals and their health benefits. Nutr J 2004;3:5.
3. Wattel A, Kamel S, Prouillet C, et al. Flavonoid quercetin decreases osteoclastic differentiation induced by RANKL via a mechanism involving NFkappaB and AP-1. J Cell Biochem 2004;92:285–95.
4. Woo JT, Nakagawa H, Notoya M, et al. Quercetin suppresses bone resorption by inhibiting the differentiation and activation of osteoclasts. Biol Pharm Bull 2004;4:504–9.
5. Wattel A, Kamel S, Mentaverri R, et al. Potent inhibitory effect of naturally occurring flavonoids quercetin and kaempferol on in vitro osteoclastic bone resorption. Biochem Pharmacol 2003;65:35–42.