Effect of coffee consumption on bone metabolism

The effects of coffee on bone metabolism are still controversial, although several studies have suggested that caffeine and/or heavy coffee consumption is associated with a significant increase in risk of fracture, osteoporosis, and periodontal disease. Therefore, we sought to clarify the relationship between coffee consumption and bone metabolism using male Wistar rats. Forty-eight male Wistar rats were assigned to three treatment groups including a control-diet group (control, n = 16, coffee-free diet), a 0.62% coffee-diet group (low caffeine, n = 16, diet supplemented with 6.2 g/kg of the control diet), and a 1.36% coffee-diet group (high caffeine, n = 16, diet supplemented with 13.6 g/kg of the control diet), and animals were maintained on an experimental diet for 140 days. Although caffeine in serum was not detected in rats fed the control diet, low-intake coffee for 140 days led to an increase in caffeine concentration to 0.53 +/- 0.11 microg/mL and high-intake coffee led to an increase of 1.77 +/- 0.22 microg/mL. No significant differences in body weight change, serum and urinary biochemical markers of bone metabolism, and bone histomorphometry were found between the coffee-diet groups and the control-diet group, except that urinary phosphorus excretion after 140 days of both coffee diets was significantly increased compared with controls (p < 0.05). In addition, the coffee diets were not associated with differences in tumor necrosis factor-alpha and interleukin-6, which have been implicated in the pathogenesis of bone loss together with interleukin-1beta. In conclusion, the present study strongly indicates that coffee does not stimulate bone loss in rats.