A large new study has linked several genetic variants associated with coffee drinking. The genome-wide meta-analysis study, led by Harvard School of Public Health and Brigham and Women’s Hospital researchers, has identified six new genetic variants connected with habitual coffee drinking. This study assists in explaining why a certain amount of coffee or caffeine effects people differently and provides a genetic basis for future research to explore the relationship between coffee and health. The study appears online in the October 7, 2014 issue of Molecular Psychiatry.

The study’s lead author, Marilyn Cornelis, research associate in the Department of Nutrition at Harvard School of Public Health, said in a statement, “Coffee and caffeine have been linked to beneficial and adverse health effects. Our findings may allow us to identify subgroups of people most likely to benefit from increasing or decreasing coffee consumption for optimal health.”

Although genetics have long been thought to contribute to individual variations in response to coffee and caffeine, narrowing down specific genetic variations has been difficult.

The study researchers, part of the Coffee and Caffeine Genetics Consortium, conducted a genome-wide meta-analysis of over 120,000 routine coffee drinkers of European and African American ancestry.

Researchers discovered two variants mapped to genes involved in caffeine metabolism, POR and ABCG2. Two variants were found near genes BDNF and SLC6A4 that may influence caffeine’s reward effects, while two others near GCKR and MLXIPL, genes involved in glucose and lipid metabolism, had not yet been linked to coffee’s metabolism or neurological effects.

According to MedlinePlus, caffeine is a bitter substance found in coffee, soft drinks, chocolate, kola nuts, tea and certain medications. The substance effect’s the body’s metabolism, including stimulating the central nervous system.