Women who drank more than five cups of coffee a day after age 65 had lower bone mineral density than lighter drinkers, according to a decade-long analysis of nearly 10,000 American women. The work, led by researchers at Flinders University in Australia, was published in the journal Nutrients in November 2025 and drew on the long-running Study of Osteoporotic Fractures, funded by the National Institute on Aging and the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
For most coffee drinkers, the news is reassuring. Moderate consumption of about two to three cups per day showed no harmful association with bone mineral density, and tea drinking was linked to slightly stronger hips. Only the heaviest coffee habit stood out as a possible problem.
What the researchers actually measured
The team, led by Ryan Yan Liu and Adjunct Associate Professor Enwu Liu, analyzed data from 9,704 women who were 65 or older when they enrolled. Beverage intake was recorded across several visits, and hip and femoral neck bone mineral density were tracked with dual-energy X-ray absorptiometry over roughly a decade. Bone mineral density, a standard measure of bone strength, is used to gauge osteoporosis risk.
Across the full group, coffee consumption showed no significant overall association with hip or femoral neck bone density. The negative signal appeared only at the top of the dose curve. Above five cups a day, higher intake tracked with lower bone density, and the effect was more pronounced in women with higher lifetime alcohol intake.
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Tea told a different story. Tea drinkers had modestly higher total hip bone density than non-drinkers, with a mean difference of 0.003 g/cm² (95% CI 0.000 to 0.005; p = 0.026). The gap was small, but statistically significant, and appeared particularly beneficial for women with obesity.
Why caffeine and bone health are linked
The mechanism has been studied for years. Caffeine can interfere with calcium absorption and bone metabolism in laboratory work, and older research has found that intakes above 300 mg per day accelerate spinal bone loss in some postmenopausal women. A standard 8-ounce cup of brewed coffee contains roughly 80 to 100 mg of caffeine, so a five-cup habit sits near or above that threshold before counting espresso drinks or energy drinks.
Tea, which also contains caffeine, appears to carry compounds that push in the other direction. Catechins, a group of plant antioxidants concentrated in tea leaves, may support bone formation and slow bone breakdown, the Flinders team notes.
What it means for your morning routine
The authors are careful not to overstate the finding. "Even small improvements in bone density can translate into fewer fractures across large groups," Enwu Liu said in the Flinders release, adding that the results do not mean people need to give up coffee or start drinking tea by the gallon.
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For readers who drink one, two or three cups a day, the study offers no reason to change course. For those regularly clearing five cups, cutting back, adding milk for calcium, or swapping a cup or two for tea are all reasonable adjustments to discuss with a doctor, especially for women with higher alcohol intake. The full paper is available open access in Nutrients under DOI 10.3390/nu17233660.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.