Ah, coffee—the beverage that makes the world go ‘round. This simple brew has been shown to not only increase longevity and enhance exercise performance, but also reduce the risk of type 2 diabetes and fight cancer. Now, we can add increased bone strength to the list of coffee’s many health benefits—thanks to new research published in The Journal of Clinical Endocrinology & Metabolism (JCEM).
Researchers from the University of Hong Kong found that coffee lovers tend to have stronger bones than their non-coffee drinking peers. Specifically, they found a robust association between habitual coffee consumption and the prevention of bone fractures in later life. The results are both surprising and significant because they run counter to decades of prior findings on the subject of coffee and bone health.
Some researchers have argued that coffee may adversely affect bone density and lead to osteoporosis, given the negative effect of caffeine on calcium absorption. But many of these studies have remained inconclusive, with researchers often reporting conflicting results.
“Inconsistent associations between coffee consumption and bone mineral density (BMD) have been observed in epidemiological studies,” wrote the authors of the JCEM report. “Moreover, the relationship of bioactive components in coffee with BMD has not been studied.”
This inconsistency in the literature led researchers of the current study “to identify coffee-associated metabolites and evaluate their association with BMD.” To that end, they assessed 564 healthy community-dwelling Chinese adults previously enrolled in the Hong Kong Osteoporosis Study—a large prospective cohort that began in 1995 to investigate the incidence of osteoporosis. The researchers separated self-identified coffee drinkers from abstainers, and asked participants to record the frequency of their coffee consumption.
They compared the BMD of those who reported drinking coffee regularly with those who didn't, and found that daily coffee drinkers had significantly higher BMD. Specifically, the researchers identified 12 serum metabolites that were much more highly concentrated among regular coffee consumers.
“Three metabolites, in particular, were associated with an increase in bone density in the population, and also, a decrease in the risk of fracture,” said Cleveland Clinic’s Chad Deal, MD, who did not take part in the study.
The metabolite 5-acetylamino-6-formylamino-3-methyluracil (AFMU; β = 0.012, SE = 0.005; P = 0.013) was significantly correlated with BMD at the lumbar spine, while 3-hydroxyhippurate (β = 0.007, SE = 0.003, P = 0.027) and trigonelline (β = 0.007, SE = 0.004; P = 0.043) were significantly associated with BMD at the femoral neck.
“Among these  metabolites, 11 known metabolites were previously identified to be associated with coffee intake and 6 of them were related to caffeine metabolism. Habitual coffee intake was positively and significantly associated with BMD at the lumbar spine and femoral neck,” the authors wrote.
Although the study was relatively small and largely based on self-reported data, some health experts, including Dr. Deal, have suggested that it offers sufficiently robust evidence in spite of its limitations. He noted that a potential benefit from this research comes from the identification of specific metabolites in coffee that are good for bone health—a discovery that could translate to the development of new drugs to help protect bone health in the future.
“For all those folks who drink lots of coffee and are concerned about the health effects of coffee, this is good news,” he said. “It appears to show that coffee is, in general, probably good for bone health.”
That said, Dr. Deal also advised heavy coffee drinkers with known low bone mass to test for calcium excretion levels, as caffeine is known to naturally increase the excretion of calcium through urine.
Furthermore, a final word of caution: Despite coffee’s host of positive health effects, the popular beverage does have its downsides. In addition to causing “the jitters” and restlessness in some folks, drinking coffee can raise cholesterol levels in select populations, as well as increase the risk of bladder cancer in males and non-smokers with high coffee consumption.
So, before you pick up that next cup o’ joe, be sure to carefully weigh the pros and cons, and remember—everything in moderation.