Heavy coffee consumption may be associated with slightly lower bone mineral density in older women, while regular tea drinking may be linked to modestly higher bone density at the hip, according to a long-term Australian analysis.
Researchers from Flinders University analyzed data from nearly 10,000 women aged 65 and older who were followed for about a decade. Their findings, published in Nutrients, suggest that the relationship between these commonly consumed drinks and bone health may depend partly on how much is consumed.
How the long-term study worked
The researchers used data from the Study of Osteoporotic Fractures, a large observational study examining bone health in older women. Participants reported their coffee and tea consumption, while bone mineral density was measured at multiple points during follow-up.
The analysis focused on bone mineral density at the total hip and femoral neck, areas that are clinically important because lower density is associated with greater fracture risk.
Researchers accounted for a range of factors that could influence bone health, including age, body weight, smoking, alcohol consumption and other lifestyle and medical characteristics.
Because the study was observational, however, it cannot establish that coffee caused lower bone density or that tea directly protected bones.
Tea linked to slightly higher bone density
Women who drank tea had modestly higher bone mineral density at the hip than women who did not drink tea. The difference was small but statistically significant.
One possible explanation involves tea polyphenols, including catechins. Previous research has investigated whether these compounds may influence processes involved in bone formation and breakdown.
However, the current study did not demonstrate that polyphenols were responsible for the association. Tea drinking could also be linked with other dietary, behavioral or socioeconomic factors that influence bone health.
The findings therefore suggest an association rather than evidence that adding tea to the diet will increase bone density.
Very high coffee intake showed a different pattern
Coffee consumption was not uniformly associated with poorer bone health. Moderate consumption of around two to three cups per day was not linked to meaningful reductions in bone mineral density in the study.
Differences became more apparent among women consuming more than five cups of coffee per day, who had lower bone mineral density at important hip sites compared with women consuming less coffee.
Caffeine has previously been studied for its potential effects on calcium absorption and bone metabolism. These effects are generally considered relatively small and can also depend on factors such as overall nutrition and calcium intake.
The findings therefore do not suggest that coffee itself is harmful to bones at typical levels of consumption. Instead, they raise questions about whether very high long-term intake could be relevant to bone health in some older women.
Alcohol and body weight may influence the associations
The relationship between beverage consumption and bone density also appeared to vary according to other characteristics.
The negative association involving higher coffee consumption was more pronounced among women with greater lifetime alcohol exposure. This does not establish that alcohol and coffee together cause bone loss, but suggests that their relationship with bone health may differ across groups.
The association between tea consumption and higher bone density was also more apparent among women with obesity.
These subgroup findings should be interpreted cautiously, particularly because observational analyses involving multiple interacting factors can produce associations that require confirmation in other populations.
What the findings mean for daily habits
The differences in bone mineral density identified in the study were relatively small. The results therefore do not provide a reason for older women to stop drinking coffee, particularly at moderate levels.
They also do not establish that drinking tea prevents osteoporosis or fractures. Bone mineral density is an important indicator of skeletal health, but the study’s beverage associations should not be interpreted as direct evidence of fracture prevention.
For older adults, established measures for maintaining bone health include adequate nutrition, sufficient calcium and vitamin D, regular weight-bearing and muscle-strengthening physical activity, and avoiding smoking. Individual osteoporosis risk can also depend on age, medications, medical conditions and previous fractures.
The study nevertheless provides useful information about two beverages consumed regularly by millions of people. Moderate coffee intake was not associated with meaningful bone-density reductions, while very high consumption of more than five cups per day was associated with lower measurements in some women.
Tea consumption, meanwhile, was associated with slightly higher hip bone mineral density, although further research is needed to determine whether tea itself is responsible for the difference.
The work was supported by the U.S. National Institute on Aging and the National Institute of Arthritis and Musculoskeletal and Skin Diseases. Because the participants were women aged 65 and older, additional research will be needed to determine whether similar patterns occur in men and younger populations.
