You’ve found your perfect blend and your perfect brewing style. Now you just need to find the perfect amount of coffee to drink.

Researchers from the Harvard School of Public Health and Brigham and Women’s Hospital identified six gene variants that influence how caffeine works in the body. The results were based on a genome-wide meta-analysis of more than 120,000 American coffee drinkers of European or African ancestry.

One set of two gene variants may influence the way caffeine lights up the brain’s reward system. Another set of two variants influences how caffeine is metabolized, and a final set was associated with the metabolic and neurologic effects of caffeine.

Identifying these genes may help researchers figure out which coffee drinkers could benefit by drinking more or fewer cups of coffee.

Future findings may also show whether coffee drinkers’ genes cause them to modulate their intake, which may explain why some people benefit from just one cup while others may visit the coffee pot all day long.

Studying these gene variants may help researchers determine what the optimal amount of coffee is for a person. Past studies have linked coffee drinking to poor health outcomes, but that was in part because former research didn’t always separate coffee drinking from risky health behaviors that often went along with it, such as smoking and being sedentary.

Now, studies have been showing some health benefits, such as protection against Type 2 diabetes.

Other studies suggest a lower risk of death from cirrhosis, decreased risk of liver cancer, a lowered risk of Parkinson’s disease, and, in moderation, protection against heart failure.

Science’s next job? To ask your genes: Will that be one cup, or two?