Osteoporosis is a major global public health concern, commonly characterised by low bone mineral density. Reduced bone density increases fracture risk, potentially leading to substantial healthcare costs and long-term disability. Lifestyle and dietary factors may have an important influence over bone health, making it essential to identify beneficial habits that improve public health and reduce strain on healthcare services.  

Caffeine, a major bioactive ingredient in both coffee and tea, has been the focus of numerous studies for its potential effects on health outcomes. Research published in the Open Access journal Nutrients examined the long-term effects of coffee and tea consumption on bone mineral density, focusing specifically on women over 65 years old. 

Bone mineral density was measured in 9704 women aged over 65, alongside self-administered questionnaires describing an individual’s coffee and tea consumption. Data was collected every two years over a 10-year period. Findings suggested that tea consumption was associated with higher hip bone mineral density, while excessive coffee intake may have adverse effects. Using data from a large cohort over an extended period strengthens the reliability of these conclusions and helps capture changes in bone health over time.    

Bone health in ageing populations 

Osteoporosis is often asymptomatic; many affected patients are unaware of its presence until they sustain a fracture. Ageing leads to increased bone fragility, and consequently, one in three women and one in five men over 50 will experience an osteoporotic fracture in later life. The higher prevalence of the condition in women can be partially attributed to the accelerated bone loss experienced in the first few years after menopause.  

The study examined bone mineral density of the femoral neck and hip bones. These areas are of clinical interest because hip fractures are a leading cause of severe health complications, particularly in older adults. Assessing bone strength in this region helps identify individuals at higher risk of sustaining a hip fracture.  

The femoral neck is especially informative because it contains a higher proportion of soft, spongy bone. This type of bone loses density earlier than harder, more compact bone, making it a better indicator of early bone loss. 

Dual-energy X-ray absorption is the gold standard for measuring bone mineral density. This technique passes two X-ray beams of differing energies through the body. Bone and soft tissue absorb these X-rays differently due to their distinct compositions. Using two different X-ray energies allows the scanner to distinguish bone from surrounding soft tissue, leading to a more accurate measurement of bone density. 

Evaluating the long-term effects of coffee and tea intake on bone mineral density in older women could unveil everyday habits that either support or harm bone health in a group particularly affected by osteoporosis. As Dr. Enwu Liu, lead author of the study, explains: 

“While calcium and vitamin D remain cornerstones of bone health, what’s in your cup could play a role too… Even small improvements in bone density can translate into fewer fractures across large groups” 

A decade of tracking bone density

Participants were drawn from the Study of Osteoporotic Fractures and followed for approximately 10 years with repeated clinical assessments.  

Information on their coffee and tea consumption was collected through questionnaires administered every two years. Bone mineral density was measured using dual-energy X-ray absorption on visits 2, 4, 5, and 6, covering the full 10-year follow-up period. Visits 1, 3, and 7 were excluded due to the unavailability of either bone mineral density or beverage intake data. 

As the study progressed, participants who had missing bone mineral density data, or were no longer able to take part in the study, were excluded from subsequent measurements. Of the 9704 women initially enrolled in the study, 4697 had bone mineral density data measured at the sixth visit. 

To account for other lifestyle factors that influence bone health, information on several additional variables was also collected. These included: 

• Age 

• Body mass index 

• Smoking 

• Physical activity 

• Diet 

• Medical history 

• Alcohol intake 

• Hormone use 

A linear mixed model approach was taken to assess the correlation between coffee and tea intake and bone mineral density. This statistical technique is commonly used in repeat-measure studies, it accounts for multiple measurements taken from the same individual over time by allowing each participant to have a unique baseline bone mineral density. The model also accounts for relevant variables that influence bone health. This enables a more accurate estimation of the independent associations between beverage intake and bone mineral density  

Beverage intake may influence bone health 

As expected, the average bone mineral density of both the femoral neck and hip declined over the 10-year follow-up period. Coffee consumption was not significantly associated with the bone mineral density at either site. Tea consumption was also not associated with femoral neck bone mineral density. However, it was linked to slightly higher hip bone mineral density. 

After adjusting for other factors that affect bone health, tea drinkers had an average hip bone mineral density of 0.718 g/cm², compared with 0.715 g/cm² in non-tea drinkers. This represents a difference of 0.003 g/cm². While modest, further analysis indicated that the difference was statistically significant and unlikely to be due to chance alone. 

Utilising natural spline regression allowed the researchers to explore non-linear trends between daily coffee and tea intake and bone mineral density. Three key findings emerged: 

• Consuming more than 5 cups of coffee a day may be linked to lower bone mineral density. 

• Evidence suggested a negative association between coffee consumption and femoral neck bone mineral density in women with a higher alcohol intake. 

• A weak linear relationship emerged for cups of tea consumed per day and hip bone mineral density. 

Professor Enwu Liu summarises the impacts of the findings: 

“Our results don’t mean you need to give up coffee or start drinking tea by the gallon… 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, tea, and bone health 

This study adds to a growing body of research examining how coffee and tea consumption affect bone mineral density. Previous findings on coffee intake have been inconsistent, with some studies suggesting a neutral or even protective effect on bone health. Mechanistically, caffeine has been shown to impair the activity of osteoblasts, the specialised cells that build new bone tissue. Despite this, research has demonstrated that the effect seems minimal and may be offset by adding milk to coffee. 

Tea consumption has generated similar debate, though evidence from studies in older women tends to be more favourable. Tea contains catechins, bioactive compounds thought to stimulate osteoblast activity while inhibiting osteoclasts, the cells responsible for bone breakdown. This dual action suggests a potential benefit for maintaining bone mineral density.  

The study’s strengths lie in its large cohort and long-term, repeated measurements, which help reduce random error. The use of linear mixed effects modelling also allowed the researchers to account for changes in consumption patterns and other variables over time, offering a more realistic assessment of how coffee and tea intake relate to bone health in older women.  

From research to real-world health advice 

Despite its strengths, the study has notable limitations. Relying on data provided through questionnaires introduces a large amount of recall bias. Data was collected on the number of beverages drunk; however, specific information on cup size, beverage strength, and coffee or tea types would provide a more detailed description on beverage intake.  

Additionally, the study cohort consisted of predominately older white women from the United States. The limited racial diversity restricts the application of these results to broader populations, where genetic factors could influence the association between beverage intake and bone mineral density. 

While the observed bone mineral density between tea drinkers and non-tea drinkers of 0.003 g/cm² was statistically significant, it falls below the threshold typically considered clinically meaningful. This suggests that tea consumption alone is unlikely to be recommended as a treatment strategy for improving bone health. 

Tea may not be prescribed for bone conditions anytime soon, but from a public health perspective these results may be relevant. Over such a large population, even minor improvements may help reduce the incidence of osteoporotic fractures. This highlights the value of research that identifies accessible lifestyle factors capable of supporting long-term health.  

More studies on bone health can be found across the Open Access journals Osteology and Nutrients. Alternatively, you can access the full MDPI journal list here.