Are coffee drinkers healthier than non-drinkers?

For the study, researchers from the University of Oulu in Finland analyzed data from 2,264 participants who were all 46 years old and part of the Northern Finland Birth Cohort 1966. The researchers examined how participants' coffee consumption affected circulating metabolites, cardiometabolic risk markers, and sex hormones.

Overall, the researchers found that people with higher coffee consumption had lower levels of both total body and visceral fat, as well as greater skeletal muscle mass, compared to those with lower coffee consumption — even when their BMIs were similar.

Higher coffee consumption was also associated with lower levels of branched-chain amino acids (BCAAs). Elevated levels of BCAAs in the bloodstream have been linked to health conditions like insulin resistance, type 2 diabetes, cardiovascular disease, fatty liver disease, and increased hypertension risk.

Notably, the researchers found certain sex-specific associations when it came to coffee drinking. In men, higher coffee consumption was linked to a more favorable glucose-insulin profile, higher levels of total and bioavailable testosterone, and increased concentrations of sex hormone-binding globulin (SHBG). However, levels of free testosterone and free androgen hormones were lower.

By comparison, women had fewer hormonal associations with coffee drinking, with higher consumption mainly associated with increased SHBG and lower levels of free androgens.

"Coffee is consumed by millions of people every day, yet we still know surprisingly little about how it relates to our metabolism and hormones," said Luca Verroest, lead author of the study and a doctoral researcher at the University of Oulu. "What stood out in our findings was a distinct hormonal signature that didn't disappear even after we took into account BMI and lifestyle factors, with several of these associations differing between men and women."

In a new study published in Nutrients, researchers also found that women who had high coffee consumption (more than five cups a day) had lower bone density than those who drank less coffee. Lower bone density can increase the risk of osteoporosis, a common health condition that affects one in three women over 50 and causes millions of fractures every year.

"Coffee's caffeine content … has been shown in laboratory studies to interfere with calcium absorption and bone metabolism, though these effects are small and can be offset by adding milk," said Ryan Liu, one of the study's authors from Flinders University.

In general, FDA says that most adults can safely consume 400 milligrams of caffeine per day, which is roughly equivalent to four eight-ounce cups of brewed coffee or six espresso shots. For pregnant individuals, the American College of Obstetricians and Gynecologists recommends 200 milligrams of caffeine per day.

Rob van Dam, a professor of exercise and nutrition sciences at the Milken Institute School of Public Health at George Washington University, said FDA'S 400-milligram guideline is reasonable for most adults and fits with what the research says you should consume to reap health benefits while avoiding negative side effects.

Two to four cups of coffee a day is "kind of a sweet spot," van Dam said. How you take your coffee can also affect its health benefits, with black coffee associated with more health benefits than coffee with sugar and creamer.