Long-term consumption of black, green or oolong tea can help strengthen bones, according to researchers from the National Cheng Kung University Hospital in Tainan, Taiwan.
People who drank an average of nearly two cups a day of these three tea varieties over a six-year period were shown to have a significantly higher bone density than people who did not drink tea, or who drank it in smaller quantities.
Writing in the 13 May edition of Archives of Internal Medicine, the researchers said they had surveyed 1,037 men and women aged 30 and older about their tea-drinking habits, as well as testing their bone-mineral density. They also accounted for other factors such as gender, age, body-mass index and lifestyle which could affect bone density.
Almost half of those taking part in the study were habitual tea drinkers, who had drunk tea on a regular basis for at least a year. Most of them drank green or oolong tea without milk, which contains calcium, itself used to strengthen bones.
Both green and oolong teas are common in Asia, although black tea is the more popular variety in the West. All three varieties come from the same plant, but are processed differently.
The researchers discovered that people who said they had consumed tea regularly for more than ten years had the highest overall bone-mineral density. In fact, their hip-bone density was 6.2 per cent higher than in non-habitual tea drinkers. Habitual drinkers over a six to 10 year period had hip-bone density 2.3 per cent higher than in non-habitual tea drinkers.
There were no significant differences between tea drinkers of one to five years and non-habitual drinkers. Similar results were found regardless of type of tea consumed.
The varying findings "may result from different study designs, inconsistent definition of tea intake categories and incomplete adjustment of the confounding effects of lifestyle characteristics such as exercise, alcohol intake and smoking", according to Dr Chih-Jen Chang, one of the study's authors.
He stressed that further research was necessary to discover whether it was in fact the flavanoids in tea which helped increase bone density, or whether it was other factors in the lifestyle of habitual tea drinkers which affected bone strength.