Coffee and tea consumption may have unique, but opposite, effects on bone health in postmenopausal women, a new long-term study has found. Coffee was linked to reductions in bone mineral density (BMD), though only at high levels of consumption, and tea was associated with improvements in total hip BMD, though only to a small degree.

“Our results don’t mean you need to give up coffee or start drinking tea by the gallon,” said co-author Enwu Liu, PhD, adjunct associate professor with the College of Medicine and Public Health at Flinders University, in Adelaide, Australia. “But they do suggest that moderate tea consumption could be one simple way to support bone health, and that very high coffee intake might not be ideal, especially for women who drink alcohol.”

Coffee and tea are among the most widely consumed beverages worldwide, but evidence of their effects on bone health remain inconclusive, Liu and colleague wrote in the study, published in Nutrients. Their research aimed to assess the longitudinal impact of coffee and tea in postmenopausal women.

Effects Are Small

For their study, the researchers analyzed data from 9704 women aged 65 years or older who participated in the prospective Study of Osteoporotic Fractures (SOF) and attended study visits 2, 4, 5, and 6, which spanned approximately 10 years.

SOF participants completed self-administered questionnaires about coffee and tea intake, which were used to assess consumption. The researchers also used measurements of femoral neck and total hip BMD taken using DEXA at the study visits.

Overall, patients had a mean age of 73 years at baseline, and their mean BMI remained relatively stable at about 26 throughout the study period.

After adjusting for key confounders, including demographic, physical activity, comorbidities, and medication use, tea consumption was positively associated with total hip BMD (least squares [LS] mean, 0.718 vs 0.715 g/cm²; mean difference, 0.003; P = .026) at a median follow-up of 8 years.

The dose-response relationship between tea consumption and total hip BMD was weak (β, 0.0006; P for linearity = .0887).

In terms of coffee consumption, the study showed no significant overall association between moderate coffee consumption (two or three cups per day) and femoral neck or total hip BMD. However, a natural spline regression analyses indicated that consumption of more than five cups of coffee per day may be associated with lower BMD.

Subanalyses showed that coffee consumption was negatively associated with femoral neck BMD among women with a higher lifetime alcohol intake (P for interaction = .0147).

“While moderate coffee drinking appears safe, very high consumption may not be ideal, especially for women who drink alcohol,” Liu said.

Meanwhile, women with obesity showed greater benefits from tea consumption than those without obesity (LS mean difference, 0.001).

“These subgroup findings should be interpreted with caution as they are likely underpowered and may be susceptible to type I error; they are primarily hypothesis-generating and warrant validation in future, larger studies,” the authors wrote.

Adding Context

In postmenopausal women, BMD normally declines with age at a rate of about 0.002-0.006 g/cm²/y, Liu said.

“Therefore, the observed difference of 0.003 g/cm² at the hip corresponds to roughly a 1-year delay in age-related BMD decline among tea drinkers compared with nondrinkers,” he told Medscape Medical News. “Although this difference may appear modest at the individual level, when considered across the large population of tea consumers, the potential public health impact is meaningful.”

With BMD in human populations generally evenly distributed, “even a small shift in mean BMD reflects a true population-level difference between tea drinkers and nondrinkers,” he added.

The findings are consistent with previous research suggesting that tea consumption may support bone health in older women; however, the collective evidence is “not yet robust enough to support a formal clinical recommendation to drink tea solely for bone preservation,” Liu noted.

Study limitations included the self-reported nature of the questionnaires and the lack of information about cup size, brew strength, and beverage types, the authors noted. Additionally, the study population consisted almost entirely of older White women in the US, limiting its generalizability to other populations.

Possible Mechanisms

Caffeine may play a role in coffee’s potential impact on health, the authors wrote. It acts as a nonspecific antagonist of adenosine receptors, which may inhibit bone formation and enhance bone resorption. In vitro studies have suggested that caffeine may downregulate vitamin D receptor expression and impair osteogenic actions of 1,25-dihydroxyvitamin D₃ in osteoblasts.

However, studies in humans suggest that in individuals with inadequate calcium intake, caffeine only has a minimal effect, “causing only a slight negative calcium balance due to reduced absorption efficiency,” the authors wrote.

Potential mechanisms underlying tea’s effects on BMD may involve catechins, particularly epigallocatechin, which can promote osteoblast activity and inhibit osteoclast differentiation, the authors noted.

“Different types of tea, including black, green, oolong, and decaf tea, contain bioactive compounds such as flavonoids and catechins, which are also found in fruits, vegetables, and dark chocolate, and have been linked to better bone health,” Liu told Medscape Medical News.

However, to date, “there is no convincing evidence that any specific type of tea is more beneficial than others for bone health,” he said.

High consumption of sugar is associated with poorer bone health, so “if tea is consumed, it is preferable to choose unsweetened varieties without added sugar,” Liu said.

First author Ryan Liu, also of the College of Medicine and Public Health, Flinders University, noted that the findings regarding tea are encouraging, even if the benefit is small.

“While calcium and vitamin D remain cornerstones of bone health, what’s in your cup could play a role too,” he said. “For older women, enjoying a daily cup of tea may be more than a comforting ritual, it could be a small step toward stronger bones.”

The study had no external funding. The authors had no disclosures to report.