Apparently, for 54 percent of the population, a couple cups of coffee daily increases your likelihood of heart attack by a third. The key is a gene, CY1A2, which we all have two copies of. A bit over half of us, though, have a mutated form that impedes caffeine metabolization. If you've got the mutation, a couple cups a day begins playing havoc with your heart. This isn't terribly surprising: caffeine constricts blood vessels, screwing with their normal functioning. It also, for reasons that are not well understood, increases the rate of harmless heart palpitations among susceptible portions of the populace (these are the skipped beats -- which are actually double-beats -- you always hear about, PVC's and PAC's). As for me, I almost certainly have this mutation. I'm not a coffee drinker, so I've no tolerance for the stuff, but a single cup in the morning will have me buzzing in the evening. Lucky thing, then, that I never got into it in the first place.