The latest study finds that the pros and cons of drinking coffee actually depend on individual genes.

People often read about coffee in newspapers and magazines, some of which may explain the disadvantages of drinking too much coffee, and some will tell you how many cups of coffee you need to drink a day to get a certain health benefit, which is really difficult to judge.

People often read about coffee in newspapers and magazines. Some may explain the bad effects of drinking too much coffee, while others may tell you how many cups of coffee you need to drink a day to get a certain health benefit. It is really difficult to judge.

But a new study published in the journal Molecular Psychiatry suggests that the amount of coffee you should drink each day depends on your genes, and that your body automatically adjusts your coffee intake for optimal results.

Researchers from the Harvard School of Public Health and Brigham and Women's Hospital recently conducted a meta-analysis of 120,000 coffee drinkers of American, European, and African descent.

They found that two genetic variants, POR and ABCG2, are involved in caffeine metabolism, and two other variants, BDNF and SLC6A4, may affect caffeine triggering of reward mechanisms. The researchers also identified for the first time two genes involved in glucose and fat metabolism, GCKR and MLXIPL, which are linked to caffeine's effects on the nervous system and metabolism.

According to Marilyn Cornelis, a nutrition research assistant at Harvard University and lead author of the study, the new candidate genes are not from genes that have been previously looked at, so this is a very important step in coffee research. Their study may help identify those most likely to reap health benefits from increasing or decreasing coffee intake.

The new study is based on a previous study published in the American Medical Association that found that the question of how much coffee an individual drinks is healthy depends on the individual's genetic profile.

In the 2006 study, individuals with the gene type that metabolizes caffeine more quickly had a reduced risk of heart attack if they drank three cups of coffee a day, but those with the gene that metabolizes coffee more slowly had a 36 percent increased risk of heart attack if they drank three cups of coffee a day, compared with those with the same gene who drank only one cup of coffee a day.

Daniel Chasman, an assistant professor at Brigham and Women's Hospital and author of the new study, said his team's findings provide more evidence that genes can influence the effects of caffeine on individuals.

Similar to previous genetic analyses of smoking and alcoholism, he said, this study is an example of how genes influence an individual's behavior.