Nearly 400 million cups of coffee are consumed every day in America. Drinking large amounts of coffee may be bad for under-55s, according to a new study published in Mayo Clinic Proceedings. A study of more than 40,000 individuals found a statistically significant 21% increased mortality in those drinking more than 28 cups of coffee a week and death from all causes, with a greater than 50% increased mortality risk in both men and women younger than 55 years of age. Investigators warn that younger people in particular may need to avoid heavy coffee consumption. No adverse effects were found in heavy coffee drinkers aged over 55.