Tea has a positive effect on bone mineral density (BMD) when consumed chronically, according to new findings from a 10-year observational study of nearly 10,000 older women. Meanwhile, high coffee consumption (five or more cups per day) was associated with diminished bone mineral density. The findings were published in Nutrients. However, more moderate coffee intake didn’t have a detrimental effect.

Bone mineral density is used to assess risk of osteoporosis, a condition that affects one in three women over 50 and leads to millions of fractures each year.

The researchers analyzed data from the Study of Osteoporotic Fractures, which included repeated measures of beverage intake and BMD at the hip and femoral neck.

Tea drinkers had a slightly higher total BMD than those who didn’t drink tea, to a statistically significant extent.

While two or three cups of coffee per day didn’t have any detrimental effects, consuming more than five cups per day was linked to lower BMD. Women with higher lifetime alcohol intake also appeared particularly vulnerable to coffee’s negative effects, and tea’s benefits appeared to be strongest in women with obesity.

Catechins, bioactive compounds in tea, may encourage bone formation and help to slow bone loss, the authors noted, while caffeine may very slightly interfere with calcium absorption and bone metabolism.