Regular consumption of green tea may protect against osteopenia and osteoporosis in postmenopausal women, according to findings from a Korean cross-sectional study published in Nutrients.
Investigators analyzed data obtained from the Korean National Health and Nutrition Examination Surveys performed from 2008 to 2011. Of the 37,753 survey participants, 6438 were postmenopausal women aged 50 years and older. After meeting study criteria, 3530 who reported green tea consumption underwent bone density scans. Dual-energy X-ray absorptiometry (DXA) scans provided measurements of bone mineral density (BMD) in the lumbar spine, femoral neck, and entire femur to determine osteopenia or osteoporosis.
Due to decreased estrogen production, which causes faster bone replacement rates and higher bone absorption, postmenopausal women are at a higher risk of developing osteoporosis. Polyphenols and flavonoids in green tea exhibit estrogen-like influences that decrease osteoclastic activity and increase differentiation of osteoblasts.
The researchers determined green tea consumption using a questionnaire with 9 categories: almost none, 6-11 cups/year, 1 cup/month, 2-3 cups/month, 1 cup/week, 2-3 cups/week, 4-6 cups/week, 1 cup/day, 2 cups/day, and 3 cups/day. Based on their frequency of green tea consumption over 12 months, the investigators subdivided the postmenopausal women into 1 of 3 groups: nonconsumers (n = 1893), those who drank green tea less than once a day (n = 1336), and those who drank 1, 2, or 3 cups daily (n = 301). (One cup was considered 200 mL [approximately 6.75 oz]). Lifestyle assessment questionnaires allowed the investigators to examine potential confounding variables, including medical history, coffee and alcohol intake, smoking status, physical activity levels, educational level, household income, age at menopause, and use of hormonal replacement therapy.
Women who consumed 1-3 cups of green tea daily had a lower prevalence of osteopenia and osteoporosis at all measured BMD sites (P <.001). These women were also more likely to exercise regularly (P =.004), binge drink alcohol (defined as drinking more than 5 glasses of alcohol more than once a week [P <.001]), and consume more coffee than the other groups. Postmenopausal women who did not consume green tea or consumed less than 1 cup daily had higher probabilities of osteopenia in the lumbar spine or femur than women who consumed green tea between 1 to 3 times daily.
Women who did not drink green tea had the lowest dietary intake of calcium and those who consumed less than 1 cup of green tea per day demonstrated the highest protein and total energy intake (all P <.001).
Some limitations of the study included the inability to adjust for confounding variables regarding comorbidities that could contribute to osteoporosis due to lack of information as well as the inability to determine a causal relationship between green tea intake and osteoporosis reduction due to the cross-sectional nature of the study. The authors acknowledged were unable to assess the calcium content in the water used to brew the tea, which may have also promoted bone mineralization, and that an accurate measure of dietary caffeine intake was difficult.
“Green tea intake might be beneficial for bone health,” the study authors concluded. “Prospective studies or clinical trials considering the duration, amount, and type of tea consumption are necessary to elucidate the effects of green tea on bone mineral density and the risk of osteoporosis and fracture.”
Lee DB, Song HJ, Paek YJ, Park KH, Seo YG, Noh HM. Relationship between regular green tea intake and osteoporosis in Korean postmenopausal women: a nationwide study. Nutrients. Published online December 26, 2021. doi:10.3390/nu14010087