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Drinking coffee reduces risk for death, negative health outcomes

Consuming coffee lowered the risk for death and a broad spectrum of health outcomes, according to a report recently published in BMJ.

“It is important to systematically assess the totality of higher level evidence of the effects of coffee consumption on all health outcomes,” Robin Poole, MB, ChB, MSc, of the academic unit of primary care and population sciences, University of Southampton, United Kingdom, and colleagues wrote. “This approach can help contextualize the magnitude of the association across health outcomes and importantly assess the existing research for any harm that could be associated with increased consumption.”

Researchers identified 201 meta-analyses in the Cochrane Database of Systematic Reviews, CINAHL, Embase, and PubMed for their umbrella review. AMSTAR and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) were used to assess data quality.

Poole and colleagues found that drinking coffee was more often linked to benefit than harm for a variety of health outcomes across exposures including any coffee vs. no coffee, one extra cup of coffee a day, and high consumption vs. low consumption. There was also evidence of a nonlinear association between consumption and some outcomes: the largest relative risk reductions occurred in those consuming three to four cups of coffee a day vs. none, including all-cause mortality (RR = 0.83; 95% CI, 0.83–0.88), cardiovascular mortality (RR = 0.81; 95% CI, 0.72–0.9), and CVD (RR = 0.85; 95% CI, 0.8–0.9). High vs. low consumption was associated with a lower risk for incident cancer (RR = 0.82; 95% CI, 0.74–0.89). Drinking coffee was also linked to a lower risk for type 2 diabetes; prostate, endometrial, skin and liver cancers; liver cirrhosis; dementia; gallstones; gout; Parkinson’s and Alzheimer’s diseases; and depression.

In addition, harmful associations from drinking coffee were largely voided by adequate adjustment for smoking, except in pregnancy, where high vs. low or no consumption was linked with pregnancy loss (OR = 1.46; 95% CI, 1.06–1.99), preterm birth in the first trimester (OR = 1.22; 95% CI, 1–1.49) and second trimester (OR = 1.12; 1.02–1.22) and low birth weight (OR = 1.31; 95% CI, 1.03–1.67). There was also a link between coffee drinking and risk for fracture in women but not men (RR ratio = 1.5; 95% CI, 1.2–1.88).

“Robust randomized controlled trials are needed to understand whether the observed associations are causal,” Poole and colleagues wrote. “Importantly, outside of pregnancy, existing evidence suggests that coffee could be tested as an intervention without significant risk of causing harm. Women at increased risk of fracture should possibly be excluded.”

In a related editorial, Eliseo Guallar, MD, MPH, Johns Hopkins Bloomberg School of Public Health, cautioned that doctors should not begin to recommend coffee as way to prevent disease or for health reasons.

“The evidence is so robust and consistent across studies and health outcomes, however, that we can be reassured that drinking coffee is generally safe, although some caveats apply,” he wrote, adding that these stipulations include recognizing that some population subgroups may be at higher risk for adverse events than others, the amount of coffee consumed, and the nutritional value of the food consumed with coffee.

Guallar shared Poole and colleagues’ sentiments that further research on the link between coffee and a person’s health must be completed.

“Additional studies are also needed to understand why people start and stop drinking coffee and the factors associated with coffee intake. Similarly, future studies will have to obtain more detailed information on the type of coffee beverages consumed and the circumstances associated with coffee drinking if study findings are going to be widely generalizable to all types of coffee,” he wrote. – by Janel Miller

Disclosure: Poole reports no support from any organization for the submitted work. Guallar reports no relevant financial disclosures. Please see the study for a full list of the other authors’ relevant financial disclosures.