Effects of caffeine and exercise on the development of bone: A densitometric and histomorphometric study in young Wistar rats

High doses of caffeine will induce calcium loss and influence the normal development of bone, whereas the proper exercise has positive effects on bone metabolism. This study investigated the possible effects of exercise to antagonize the caffeine-induced impairment of bone development in young male Wistar rats. A total of 32 male rats (5 weeks old) were divided randomly into four groups: group I rats were fed caffeine; group 2 rats were prescribed an exercise program; group 3 rats were fed caffeine and prescribed an exercise program; and group 4 rats served as the control group. The caffeine was fed via the animals' dietary water and the dosage was 10 mg/100 g body weight per day, 3 days a week. The exercise program was carried out on a treadmill for 10 weeks (5 days/week, 1 h/day, 70% (V) over dot O(2)max). Body weight was measured weekly. After sacrifice, the tibia length was measured and the tibia was processed for histomorphometric analysis. Bone mineral density was measured by dual-energy X-ray absorptiometer at three different sites of the tibia. In addition, the calcium content of the right femur was measured by atomic absorptiometry. The results showed that both exercise and caffeine significantly lowered the body weight gain. Rats fed with caffeine (groups I and 3) had a significantly longer tibia as compared with the non-caffeine-fed rats (groups 2 and 4) (p = 0.0149). The histomorphometry study showed that thickness of the growth plate in the proliferative zone, the hypertrophic zone, and total growth plate was greater in caffeine-fed groups than in non-caffeine-fed groups. The cell number in the proliferative zone was higher in the caffeine-fed groups. Area ratio of trabeculae in the primary spongiosa of rats in groups I and 2 were significantly greater than the control group. Caffeine feeding (groups I and 3) induced a lower area ratio of bone trabeculae in the secondary spongiosa, whereas exercise training (groups 2 and 3) increased the thickness of the trabeculae. The exercise program counteracted the negative effect of caffeine on the trabecular thickness, but did not correct the trabecular bone ratio. The bone mineral density (BMD) of the tibia was significantly lower in caffeine-fed rats, and the exercise program did not show any counteracting effect on the caffeine-induced BMD reduction. The calcium content assay showed that caffeine feeding decreased the weight and total calcium content of the femur. Again this exercise program did not counterbalance the negative effects of caffeine. In conclusion, high doses of caffeine seemed to stimulate the growth of long bone. However, it caused more serious negative effects on bone, including bone mineral loss, lower BMD, and lower calcium content. Exercise training at 70% VO(2)max had little antagonizing effect on caffeine-induced impairment of bone formation. Therefore, the best way to prevent caffeine-induced negative effects on bone development is to lower caffeine exposure. (C) 2002 by Elsevier Science Inc. All rights reserved.