SEATTLE — New study results indicate that increased intake of dietary flavonoids, such as those found in tea, may be helpful in prevention of osteoporotic bone fractures.
“Tea is associated with a reduction in all-cause fracture and hip fracture, and the effect is nonlinear,” said Richard Prince, MD, FRACP, MRCP, who is a professor at the School of Medicine and Pharmacology at the University of Western Australia in Perth.
Dr Prince, who presented the study findings at the American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting, noted that previous studies have shown beneficial effects of tea on bone structure. To learn more, he and his colleagues analyzed the association of black tea and flavonoid intake with the risk for fractures leading to hospitalization or death.
The investigators examined the data from a prospective cohort study of older women recruited to a 5-year, double-blind, randomized, controlled trial of daily calcium supplementation to prevent osteoporotic fracture (Calcium Intake Fracture Outcome Study [CAIFOS]). They were followed for another 5 years.
Dietary intake was estimated in 1188 women using a food frequency and beverage questionnaire, and flavonoid intake was calculated using U.S. Department of Agriculture flavonoid databases. The investigators then analyzed incident, verified osteoporotic fracture hospitalizations or death over a 10-year period.
A multivariate-adjusted Cox regression model was used to examine the hazard ratios (HRs) for incident fracture.
Results showed that any osteoporotic fractures occurred in 288 women (24.2%), major osteoporotic fractures occurred in 212 women (17.8%), and hip fractures occurred in 129 women (10.9%).
Compared with women drinking 1 cup of tea per week, each 1-cup per day increase in tea intake was associated with a 9% decrease in the risk for any serious osteoporotic fracture (fully adjusted HR=0.91; 95% CI, 0.84-0.99). However, after adjusting for bone mineral density, the relationship was not significant.
Overall, tea accounted for 75% of total flavonoid intake among these women, Dr Prince reported. Results revealed that women in the highest tertile of flavonoid intake vs the lowest tertile had a lower risk for serious osteoporotic fracture (HR=0.65; 95% CI, 0.47-0.88), major osteoporotic fracture (HR=0.66; 95% CI, 0.45-0.95), and hip fracture (HR=0.58; 95% CI, 0.36-0.95).
“The take-home message is that endocrinologists who are seeing bone patients should encourage their patients to continue drinking tea, if they are, and aim for more than 3 cups of tea per day. They may have a 30% lower risk of fracture over a period of 10 years,” Dr Prince said in an interview with Endocrinology Advisor.
“Beyond calcium and vitamin D intake, the current evidence is that drinking tea may be beneficial.”
The study also showed that 204 women reported drinking 1 cup of tea per week, 357 reported drinking 1 to 3 cups per week, and 627 reported drinking more than 3 cups of tea per day.
All the women lived in Australia and mainly drank black tea.
While observational studies have linked tea drinking with higher bone density, there has been a lack of prospective studies examining the association of tea drinking and flavonoid intake with fracture risk, Dr Prince explained. Therefore, these findings are welcome, as they suggest a safe and inexpensive means of lowering the risk for osteoporotic fractures.
However, though drinking more than 3 cups of tea daily may be beneficial, the tannins in tea can be a stomach irritant, so clinicians should take that into consideration when counseling patients about fracture prevention in osteoporosis.
Meryl LeBoff, MD, who is a professor of medicine in the division of endocrinology, diabetes, and hypertension at Harvard Medical School in Boston, said these findings are promising and now need to be validated in prospective studies.
“This is a very interesting observational study that showed that higher intakes of flavonoids compared with lower intakes were associated reduced fracture risk. Since fractures rise markedly with age, randomized, placebo-controlled studies are needed to test the effects of flavonoids on bone fractures and other skeletal outcomes,” Dr LeBoff noted.
President of ASBMR Douglas P. Kiel, MD, MPH, agreed with Dr LeBoff. He said the findings go well with previous research and confirms the flavonoid hypothesis.
Nevertheless, he cautioned that much more research is necessary and that patients should not get the wrong idea. Some patients may mistakenly think that they can treat osteoporosis by just drinking tea or through other nutritional steps only.
“You always have problems with this type of study because it may be that they eat sandwiches with their cups of tea, and it is not just the tea,” Dr Kiel, who is also a professor of medicine at Harvard Medical School, told Endocrinology Advisor.
“I think there could be something beneficial with tea, but everyone thinks you can treat diseased bone with nutrition. So, you don’t want someone just thinking they can drink tea or eat yogurt and that a total nutritional approach to osteoporosis is all they need.”
- Prince R. Abstract FR0309: Prevention of osteoporotic fractures by black tea consumption. Presented at: American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting; Oct. 9-12, 2015; Seattle.