We don't know. My understanding of the current meta-studies is that there is a slight positive effect on general health and life expectancy associated with dri

We don't know. My understanding of the current meta-studies is that there is a slight positive effect on general health and life expectancy associated with drinking reasonable amounts of coffee. But think about that more -- what else could be associated with drinking coffee? People who drink coffee every day might be more likely to have a job, which means (in the US) that they're more likely to have health insurance and higher socioeconomic status, which can cause increases in life expectancy too. Which suggests that it could be the case that if you're thinking about drinking coffee every day, you've probably already benefited from the positive effects regardless of whether you actually go ahead and drink it. While I don't think we're going to be able to isolate the measurement of positive effects, we can say one thing: while we can't measure causal positive effects on health, we're at least not seeing strong negative effects on health from moderate coffee drinking. The argument's just over whether coffee is causing the slightly-better health that people who drink it experience, or merely correlating with it.