A study of nearly 10,000 older women has linked heavy coffee consumption to lower bone mineral density, a finding complicated by one detail: moderate intake carries no such penalty, and the same researchers found that tea drinking is associated with better bone health.
The research, published in the journal Nutrients by scientists at Flinders University, tracked coffee and tea habits among 9,704 women aged 65 and older over a decade. The team measured bone mineral density at the femoral neck and hip, sites where osteoporosis-related fractures tend to occur. Women drinking more than five cups of coffee daily showed lower BMD at those sites. Those drinking two to three cups showed no negative association.
Study co-author Ryan Liu told ScienceDaily that compounds called catechins, abundant in tea, may promote bone formation and slow bone breakdown. Coffee's caffeine, by contrast, has been shown in laboratory studies to interfere with calcium absorption and bone metabolism, though Liu noted those effects are small and can be offset by adding milk. The interaction also varied by subgroup: coffee consumption was associated with lower femoral neck BMD specifically among women with higher alcohol intake, while the positive link between tea and bone density was more pronounced among women with obesity.
The counterargument is that the study's own authors resist a strong read-through. Liu was explicit: these results do not mean women need to give up coffee or drink tea in large quantities. The association between very high intake and lower BMD appears real in the data, but the mechanism remains partly speculative, and observational work of this kind cannot establish cause.
On balance, the evidence supports a dose story rather than a prohibition. Five-plus cups a day looks like the threshold worth watching, particularly for postmenopausal women, who already face accelerated bone loss and generally carry lower bone mass than men. The fracture burden in this population is documented at scale. The study cites figures showing roughly one in three women aged 50 and older worldwide experience osteoporosis-related fractures, and in the U.S., the number of adults 50 and older with low bone mineral density in the hip or spine is projected to increase by 17.2 million by 2030, according to the researchers.