Drinking a couple of cups of coffee each day could reduce a person's risk of death from a number of illnesses, including heart disease, a new study has found.

US researchers analysed data from three ongoing studies involving over 208,000 men and women. Coffee-drinking habits were assessed every four years over a 30-year period. During this time, almost 32,000 people died from a range of causes.

They found that people who drank a moderate amount of coffee each day - that is less than five cups - had a reduced risk of death from heart disease, type 2 diabetes and neurological disease.

These results stood irrespective of whether the coffee was caffeinated or decaffeinated. This suggests that it is not just the caffeine that benefits healths, but possible naturally occurring chemical compounds in the coffee beans.

"Bioactive compounds in coffee reduce insulin resistance and systematic inflammation. They might be responsible for the inverse association between coffee and mortality. However, more studies are needed to investigate the biological mechanisms producing these effects," the researchers said.

They acknowledged that the results should be interpreted with caution, but said that they add to previous findings which suggest that moderate coffee consumption offers some health benefits.

"Regular consumption of coffee can be included as part of a healthy, balanced diet. However, certain populations such as pregnant women and children should be cautious about high caffeine intake from coffee or other beverages," they added.

Details of these findings are published in the journal, Circulation.