Coffee has been the world’s favorite stimulant for hundreds of years, yet scientists are only now figuring out its impact on human health. In a new Journal of Internal Medicine study, scientists report that the addictive beverage has a unique impact on a person’s metabolism. In particular, coffee changes the metabolism of steroids and neurotransmitters that are usually associated with another of our favorite drugs — cannabis.

At the base level, the international team of researchers reported on Thursday, coffee shifts the levels of certain metabolites, which are chemicals in the blood that spike or drop after we eat or drink. Extremely heavy coffee drinking caused neurotransmitters related to the stress-regulating endocannabinoid system to decrease — which is the opposite of what happens after a person smokes marijuana. The researchers reasoned that the decrease in metabolites could be the body’s way of trying to get stress levels back to equilibrium after getting so hyped up on coffee.

“These are entirely new pathways by which coffee might affect health,” lead author Marilyn Cornelis, Ph.D., an assistant professor of preventative medicine at Northwestern University, explained in a statement released Thursday. “Now we want to delve deeper and study how these changes affect the body.”

Math explains how to make the perfect cup of coffee.
Scientists are still learning exactly how coffee impacts health.

For three months, the 47 study participants willingly let the scientists screw with their coffee schedule. In the first month, they didn’t drink any coffee; in the second month, they moved up to four cups a day; and in the third month, they slurped down eight cups a day (four more than what’s recommended as the healthy limit). Then, the scientists examined the hundreds of metabolites floating around in the blood samples collected after each stage of the study.

Heavy coffee drinking appeared to raise the number of metabolites linked to the androsteroid system, which helps the body get rid of steroid molecules. But the scientists also found that the blood metabolites related to the endocannabinoid system metabolic pathway decreased with coffee consumption, especially when participants were drinking eight cups of coffee a day. The endocannabinoid system regulates a wide range of functions in the body, including stress.

The body naturally produces endocannabinoids, which mimic the cannabinoid activity caused by chemicals in marijuana. But when a person smokes weed, endocannabinoid blood metabolites increase in the system — the opposite of what happens when you drink coffee.

What happens when you drink weed-infused coffee is a whole other question scientists have yet to figure out — and with the rapid legalization of marijuana, it may have to be a scientific puzzle they need to figure out soon.