Drinking more than four cups of coffee per day may endanger your health, particularly if you are under the age of 55, a new study has found.

Millions of people worldwide drink coffee on a daily basis. In the US alone, over 400 million cups of the beverage are consumed every single day.

US scientists decided to look at any links between coffee and deaths from all causes. They analysed the health details of over 43,000 men and women aged between 20 and 87 over a 17-year period. During this period, just over 2,500 of the participants died, one-third of whom died as a result of heart disease.

The study found that those who consumed more than 28 cups of coffee per week had a 21% increased risk of death from all causes. In men and women under the age of 55, this risk increased to over 50%.

The scientists noted that younger men had a higher mortality rate even if they consumed lower levels of coffee, however the risk became statistically significant at 28 cups per week. At this point, there was a 56% increase in mortality from all causes.

In younger women who drank at least 28 cups, there was a two-fold increased risk of death from all causes compared to women who did not drink coffee.

"Significantly, the results did not demonstrate any association between coffee consumption and all-cause mortality among older men and women. It is also important to note that none of the doses of coffee in either men or women, whether younger or older, had any significant effects on cardiovascular mortality," the scientists from the University of South Carolina said.

They noted that coffee is a complex beverage made up of thousands of components. While research indicates that it can have beneficial effects of cognitive function and inflammation, it has also been linked to some adverse health effects, such as increasing blood pressure and affecting insulin activity.

"Research also suggests that heavy coffee drinkers may experience additional risk through potential genetic mechanisms...We hypothesise that the positive association between coffee and mortality may be due to the interaction of age and coffee consumption, combined with a component of genetic coffee addiction," the scientists said.

While acknowledging that more studies are needed, they believe that younger people in particular should avoid heavy consumption of coffee.

Details of these findings are published in the journal, Mayo Clinic Proceedings.