Tea contains thousands of chemical compounds that may affect the human body in a number of ways. Research suggests that drinking tea may help ward off cardiovascular disease (heart disease and stroke) and some forms of cancer. Some of the compounds in tea, such as fluoride and flavonoids, may help increase or maintain bone density. However, research on how tea consumption affects bone density has produced mixed results.
Now, research recently published in the
Archives of Internal Medicine
suggests that habitual, long-term tea consumption may increase bone mineral density, thus reducing the risk of osteoporosis.
Researchers from National Cheng Kung University Hospital in Taiwan studied 1037 Chinese men and women living in Tainan, a city in southern Taiwan. The men and women were age 30 or older and had no history of a bone-remodeling disease or taking bone-remodeling medications.
During surveys in 1996-1997 and 1998-2000, trained interviewers used a structured questionnaire to interview participants about the following personal habits:
- Tea consumption (black, green or oolong) with or without milk
- Physical activity
- Intake of alcohol, caffeine, and milk
- Use of calcium supplements
- Medical history
- Body mass index (height-to-weight ratio)
Participants were then grouped according to their tea-drinking habits. Habitual tea drinkers were those who drank tea at least once per week in the preceding 6 months; non-habitual drinkers drank tea less than once per week in the preceding six months. Participants were further grouped into the following categories:
- Non-habitual tea drinkers
- Habitual tea drinkers for 1 to 5 years
- Habitual tea drinkers for 6 to 10 years
- Habitual tea drinkers for more than 10 years
Between 1998 and 2000, the participants underwent bone mineral density (BMD) tests of the hip, spine, and total body. Researchers compared the BMD of tea drinkers with the BMD of nondrinkers.
Overall, habitual tea drinkers had higher bone mineral density of the hip, spine, and total body than nondrinkers. The bone density among tea drinkers ranged from 0.5% to 5.1% higher than nondrinkers depending on the duration of tea drinking and the location of measurement (hip, spine, or total body). Though it may seem small, a 5%-increase in bone density translates to significant improvement in bone health.
Habitual tea drinkers of more than 10 years had the highest bone density and tea drinkers of 6 to 10 years had the next highest bone density. Number of years of tea drinking rather than daily tea intake was associated with higher bone density. Of interest is that the type of tea consumed (black, green, or oolong) did not affect bone density.
In calculating these statistics, the researchers accounted for the effects of other factors that influence bone density, such as age, menopause, body mass index, physical activity, alcohol intake, smoking, milk intake, and calcium supplementation.
Although these results are interesting, there are limitations to this study.
The study was conducted in an exclusively Asian population. If Asian people have any habits that affect bone density that differ from the habits of other ethnic and racial groups, these results may not be applicable to non-Asians. In addition, it’s quite possible that genetic factors unaccounted for in this study influence a person’s bone density. Although the researchers did assess participants’ milk intakes, they did not thoroughly examine their dietary habits for all sources of calcium and vitamin D, two very important contributors to bone density. Finally, the ability to compare bone density among black tea drinkers versus drinkers of green and oolong tea is limited by the relatively few black tea drinkers in this study. Note: In Western countries black tea is consumed more frequently than green and oolong tea.
If you’re not a tea drinker, should you start? Sure. In addition to tea’s potential for warding off cardiovascular disease and cancer, these findings suggest tea may help prevent osteoporosis by increasing bone density. In addition, these findings concur with the findings of other studies that substances in tea may, in fact, help increase and maintain bone density.
And while you’re at it, don’t be afraid to have a little milk (translation: calcium) in your tea.
Wu CH, et al. Epidemiological evidence of increased bone mineral density in habitual tea drinkers.
Archives of Internal Medicine
. May 13, 2002;162:1001-1006.
Last reviewed May 15, 2002
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