What do researchers mean when they say that coffee is a marker for an unhealthy lifestyle or dietary habit?
This means that coffee may be associated with other lifestyle or dietary habits. For example, people who smoke tend to drink more coffee. Coffee is thus a marker for smoking. This can create problems analysing epidemiological research results, for although it may appear that coffee drinking is a risk factor for a particular disease, it may simply be a marker for another lifestyle or dietary factor that is the real cause. Put simply this means that coffee itself is not actually a risk, it is simply associated with the real risk factor.
