High caffeine intake is reported as a risk factor for reduced bone mineral density (BMD) in older women. Most studies, however, are from populations in which coffee drinking predominates and is the major caffeine source. Tea contains caffeine but also has other nutrients, such as flavonoids (catechins), that may influence bone mass in different ways. The amino acid theanine, present in tea, is also reported to counteract the stimulant effects of caffeine.
A study performed in Britain, where tea-drinking is common, measured BMD in 1256 free living women aged 65–76 years in Cambridge, United Kingdom. There were 1134 tea drinkers (90.3%) and 122 non–tea drinkers (9.7%). Compared with non–tea drinkers, tea drinkers had significantly greater (5%) mean BMD measurements, adjusted for age, and significantly greater body mass index. These findings were independent of smoking status, use of hormone replacement therapy, coffee drinking, and whether milk was added to the tea. The authors concluded that nutrients found in tea, such as flavonoids, may influence BMD and offer protection against osteoporosis in older women.
American Journal of Clinical Nutrition, Vol. 71, No. 4, 1003-1007, April 2000