Marlene Busko

October 12, 2015

SEATTLE — Drinking multiple cups of black tea (as opposed to green or other tea) with or without milk was linked to a substantially lower risk of fractures in older women who participated in the Calcium Intake Fracture Outcome Study (CAIFOS) and were followed for a mean of 5 years.

Specifically, in more than 1000 women with a mean age of 75, those who drank at least three cups of tea a day had a 34% lower risk of developing a serious osteoporotic fracture and a 42% lower risk of developing a hip fracture, compared with women who rarely drank tea, in this Australian trial.

"Previous studies, including our own, have demonstrated a beneficial effect of tea, a major source of dietary flavonoids, on bone structure," Dr Richard L Prince from the University of Western Australia, in Perth, and colleagues write, in an abstract presented as a poster at the American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting. Now the current study suggests that black tea is associated with a lower risk of fracture in older women.

However CAICOS was not designed to prove cause and effect of tea drinking on fracture risk, Dr Prince cautioned in an oral presentation. Moreover, although the researchers adjusted for multiple confounders, they may have missed some, and the mechanisms that explain the beneficial effect of flavonoids on bones remains to be elucidated, he stressed.

"Some brave person needs to undertake a proper, randomized controlled trial of tea intake" and effect on bone health, Dr Prince urged, noting, however, that it is difficult to have people change their tea-drinking habits as part of a research study.

Asked by Medscape Medical News whether, in the meantime, an older women who is afraid of falling and breaking a hip should drink more tea, he replied: "Absolutely. Tell her to drink tea."

Future research might show how the effect of long-term tea drinking compares with taking therapeutic agents for fracture prevention. In the meantime, this study suggests that drinking a few cups of tea a day may be a useful added dietary preventive strategy for older women at high risk of fractures, the researchers conclude.

Inconsistent Link Between Tea Intake and Fracture Risk

"We and others have undertaken cross-sectional studies showing the relationship between tea intake and bone density at various [body] sites, but when it comes to fracture, the data have been quite inconsistent," Dr Prince and colleagues write, possibly because tea intake is nonlinear and there are large variations in tea-drinking habits in different populations.

To examine this, they analyzed data from participants in CAIFOS, a prospective cohort study of women who were randomized to take a daily calcium supplement to prevent osteoporotic fracture.

At baseline, the 1188 study participants replied to a food frequency and beverage intake questionnaire. Based on their replies, the researchers estimated the participants' flavonoid intake, using the US Department of Agriculture flavonoid database.

Three-quarters of the flavonoid intake of the participants came from tea. The women were divided into tertiles of tea consumption: up to one cup a week (204 women), one to three cups a day (357 women), and more than three cups a day (627 woman).

A total of 288 women (24.2%) were hospitalized for osteoporotic fractures during a mean follow-up of up to 10 years.

For each one-cup/day increase in tea intake, there was a 9% decrease in the risk of a serious osteoporotic fracture (P = .027), but this was no longer significant after adjustment for bone-mineral density.

Close to one in five women (17.8%) had a major osteoporotic fracture, and about one in 10 women (10.9%) had a hip fracture.

Compared with women in the lowest tertile of flavonoid intake, women in the highest tertile had a significantly lower risk of having a major osteoporotic fracture (15% vs 20%) or a hip fracture (8% vs 12%). However, drinking between one and three cups of tea a day was not significantly better than drinking one cup a week.

If You Already Drink Tea, Carry On

Passing by the poster, Dr A John Robbins, from the University of California, Davis Health System, in Sacramento, commented that this was an "interesting, not earth-shattering" study.

It would be difficult to find people who drank this much tea in the United States, he noted, and it would be "very hard to convince people to randomize between drinking tea and not drinking tea, [since] if they're tea drinkers, they will want to drink their tea." Dr Prince replied that in Western Australia, about half of the elderly women already drink three or more cups of tea a day, but young people drink less tea.

Dr Robbins asked, "How many women would have to drink black tea as opposed to not black tea to prevent a fracture?" Dr Prince replied that he had had not yet calculated number needed to treat. The heavy tea drinkers had roughly the same body weight as the other women, but they tended to eat more fruit, he added.

Dr Jerzy Przedlacki, from the University of Warsaw, in Poland, who also stopped by the poster, was happy to learn about this study, since people in Poland drink a lot of tea as opposed to coffee. He suggested to Medscape Medical News that "one explanation is maybe [the heavy tea drinkers] don't drink so much coffee." Dr Prince said that they had corrected for this and other confounders but agreed that more study is needed.

"I don't know whether my colleagues would be enthusiastic in trying to persuade people [to start drinking tea]," he added, but "I think they should agree that people should continue to take tea" if they are already drinking it.

American Society for Bone and Mineral Research 2015 Annual Meeting; October 9, 2015; Seattle, Washington. Abstract FR0309.

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