From Coffee of Science Information Center
Q: Is coffee bad for your health?
A: No. Coffee can be part of a healthy balanced diet. There is no conclusive evidence to suggest that a moderate amount of coffee is bad for you.
Q: How do we know that coffee is ‘safe’?
A: Coffee is one of the most heavily researched commodities in the world today with literally thousands of published studies covering a wide range of topics. The overall conclusion is that coffee drinking is perfectly safe
Q: I have read that some scientific papers suggest that coffee increases the risk for some diseases. Does this mean that coffee is a health risk?
A: No, research shows that coffee drinking is perfectly safe. It is inevitable, given the number of studies conducted on coffee and health, that from time to time they may suggest a link between coffee and certain conditions, however, it is important to look at the overall picture which supports that coffee drinking is no risk to the consumer. One study in isolation cannot provide this.
Q: I have seen reports in the media that suggest coffee drinking is unsafe?
A: It is important to look at the overall picture and one study taken in isolation cannot provide this. From time to time a study may suggest a health risk associated with coffee drinking, as a result of ‘confounding factors’ which may not have been fully explained or indeed understood by the media when they write about a particular study.
Q: What are ‘confounding factors’?
A: Researchers may say that their results have been affected by “confounding factors”. There are many aspects of lifestyle and diet (such as smoking, diet, age, sex, sedentary lifestyle as examples), which can affect your health. These results should be taken into account when looking at the potential effects of coffee on health, and are known as “confounding factors”. It can be very difficult to control for these when analysing the results of epidemiological research, and they can potentially cause false-positive results for coffee. Most researchers stress that their results on coffee may be affected by not having controlled for these factors.
Q: What do researchers mean when they say that coffee is a “marker” for an unhealthy lifestyle or dietary habit?
A: 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.