People who drink about three to five cups of coffee a day may be less likely to die prematurely from some illnesses than those who don’t drink or drink less coffee, according to a new study by Harvard TH Chan School of Public Health researchers and colleagues. Drinkers of both caffeinated and decaffeinated coffee saw benefits, including a lower risk of death from cardiovascular disease, neurological diseases, type 2 diabetes, and suicide.
"Bioactive compounds in coffee reduce insulin resistance and systematic inflammation," said first author Ming Ding, a doctoral student in the department of nutrition. "That could explain some of our findings. However, more studies are needed to investigate the biological mechanisms producing these effects."
Researchers analysed health data gathered from participants in three large ongoing studies: 74,890 women in the Nurses' Health Study; 93,054 women in the Nurses' Health Study 2; and 40,557 men in the Health Professionals Follow-up Study. Coffee drinking was assessed using validated food questionnaires every four years over about 30 years. During the study period, 19,524 women and 12,432 men died from a range of causes.
In the whole study population, moderate coffee consumption was associated with reduced risk of death from cardiovascular disease, diabetes, neurological diseases such as Parkinson’s disease, and suicide. Coffee consumption was not associated with cancer deaths. The analyses took into consideration potential confounding factors such as smoking, body mass index, physical activity, alcohol consumption, and other dietary factors.
"This study provides further evidence that moderate consumption of coffee may confer health benefits in terms of reducing premature death due to several diseases," said senior author DR Frank Hu, professor of nutrition and epidemiology. "These data support the 2015 Dietary Guidelines Advisory Report that concluded that 'moderate coffee consumption can be incorporated into a healthy dietary pattern.'"
Background—The association between consumption of caffeinated and decaffeinated coffee and risk of mortality remains inconclusive.
Methods and Results—We examined the associations of consumption of total, caffeinated, and decaffeinated coffee with risk of subsequent total and cause-specific mortality among 74,890 women in the Nurses' Health Study (NHS), 93,054 women in the NHS 2, and 40,557 men in the Health Professionals Follow-up Study. Coffee consumption was assessed at baseline using a semi-quantitative food frequency questionnaire. During 4,690,072 person-years of follow-up, 19,524 women and 12,432 men died. Consumption of total, caffeinated, and decaffeinated coffee were non-linearly associated with mortality. Compared to non-drinkers, coffee consumption one to five cups/d was associated with lower risk of mortality, while coffee consumption more than five cups/d was not associated with risk of mortality. However, when restricting to never smokers, compared to non-drinkers, the HRs of mortality were 0.94 (0.89 to 0.99) for ≤ 1 cup/d, 0.92 (0.87 to 0.97) for 1.1-3 cups/d, 0.85 (0.79 to 0.92) for 3.1-5 cups/d, and 0.88 (0.78 to 0.99) for > 5 cups/d (p for non-linearity = 0.32; p for trend < 0.001). Significant inverse associations were observed for caffeinated (p for trend < 0.001) and decaffeinated coffee (p for trend = 0.022). Significant inverse associations were observed between coffee consumption and deaths due to cardiovascular disease, neurological diseases, and suicide. No significant association between coffee consumption and total cancer mortality was found.
Conclusions—Higher consumption of total coffee, caffeinated coffee, and decaffeinated coffee was associated with lower risk of total mortality.