In America, almost 400 million cups of coffee are consumed each day. According to a new study published in the journal Mayo Clinic Proceedings, drinking large amounts of coffee may have adverse effects on individuals under the age of 55. A new study of more than 40,000 people found a statistical significance of a 21 percent increase of mortality in those who drink more than 28 cups per week. A 50 percent mortality risk in both men and women younger than 55 was observed. Investigators warn that younger people in particular may need to avoid heavy coffee consumption. No adverse effects were observed in individuals over the age of 55. 

According to the latest National Coffee Drinking Study from the National Coffee Association, more than 60 percent of American adults drink coffee every day, consuming an average of just over three cups.

It has been suspected that coffee contributes to a variety of chronic health conditions for a long time, even though earlier studies are limited and often controversial.

A multicenter research team investigated the effect of coffee consumption on death from all causes and deaths from cardiovascular disease in the Aerobics Center Longitudinal Study (ACLS) cohort, with an average follow-up period of 16 years and a relatively large sample size of over 40,000 men and women.

Between 1979 and 1998, almost 45,000 individuals ages 20 to 87 years old participated and returned a medical history questionnaire assessing lifestyle habits, including coffee consumption, and personal and family medical history. The investigators examined a total of 43,727 participants, 33,900 men and 9,827 women, in their final analysis.

During the 17-year average follow-up period there were 2,512 deaths, 32 percent of them caused by cardiovascular disease. Those who consumed higher amounts of coffee were more likely to smoke and had lower levels of cardiorespiratory fitness.

All participants were followed from the baseline examination to date of death or until December 31, 2003. Deaths from all causes and deaths from cardiovascular disease were identified through the National Death Index or by accessing death certificates.

Senior investigator Steven H. Blair, PED, of the Department of Biostatistics and Epidemiology, Arnold School of Public Health, University of South Carolina, emphasizes that “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.”

“Thus, all of these mechanisms could counterbalance one another. Research also suggests that heavy coffee drinkers may experience additional risk through potential genetic mechanisms or because of confounding through the deleterious effects of other risk factors with which coffee drinking is associated,” say lead authors, Junxiu Liu, MD, Department of Biostatistics and Epidemiology, and Xuemei Sui, MD, MPH, PhD, Department of Exercise Science, both at the Arnold School of Public Health, University of South Carolina, “Therefore, we hypothesize 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.”