Penn State Department of Family and Community Medicine, Penn State College of Medicine, Hershey (Dr. Malone); Torrance Memorial Physician Network, Calif (Dr. Tsai) malm0001@hotmail.com
The authors reported no potential conflict of interest relevant to this article.
Coffee is one of the most widely used botanicals with approximately 3.5 billion cups of coffee consumed per day worldwide. It is a popular beverage because of its unique aromatic taste and its use as a central nervous system stimulant. The coffee tree (genus coffea) is found throughout Latin America, Africa, and eastern Asia. Two of the most common commercially grown species are Coffea arabica (Arabicas) and Coffea canephora (Robusta). Processing and roasting methods may differ and produce variations in flavor and aroma. The degree of roasting also affects the caffeine content.
Coffee consumption leads to increased alertness and can boost mental performance. Based on the literature and US Food and Drug Administration recommendations, four 8-oz cups of coffee (about 400 mg of caffeine) daily is an acceptable average amount of caffeine. More than 500 mg/d is considered excessive use of coffee.33,34
Overall mortality.A 2008 study showed that regular coffee was not associated with increased or decreased mortality in both men and women.35 However, more recent studies show an inverse relationship between mortality and coffee consumption.
Specifically, a 2014 meta-analysis found an inverse relationship between coffee and mortality.36 A large prospective cohort study from 2015 that included 79,234 women and 76,704 men found that drinking coffee was inversely associated with overall mortality.37 In this cohort study, an inverse association were observed for deaths from heart disease, respiratory disease, diabetes, and self-harm.37 While mechanisms were not analyzed, coffee may reduce mortality risk by affecting inflammation, lung function, insulin sensitivity, and depression.
Cardiovascular disease. Coffee consumption may modestly reduce the risk of stroke, according to a prospective cohort study of 83,076 women from the Nurses’ Health Study who were followed for 24 years.38 Reduced cardiovascular mortality was also found in a large prospective cohort study, as noted in the mortality discussion above.37 A 2014 meta-analysis concluded that coffee consumption is inversely associated with cardiovascular mortality. Drinking 3 or 4 cups a day appears to be the amount that may decrease one’s risk of death when compared to those who do not drink coffee at all.36
Liver disease. Friedrich et al performed a study involving 379 patients with end stage liver disease, and found that coffee consumption delayed the progression of disease in patients with both alcoholic liver disease and primary sclerosing cholangitis.39Coffee consumptionalso increased long-term survival after liver transplantation.39 However, the study found that coffee did not have any effect on patients with chronic viral hepatitis.
In a 2016 meta-analysis, caffeinated coffee consumption reduced hepatic fibrosis of nonalcoholic fatty liver disease, although caffeine consumption did not reduce the prevalence of nonalcoholic fatty liver disease.40 Another meta-analysis, including 16 studies, also found caffeine reduced the risk for hepatic fibrosis and cirrhosis.41
Depression. Based on 2 different systematic reviews and meta-analyses from 2016, coffee consumption appears to have a significant protective effect, decreasing the risk of developing depression.40,42
Alzheimer’s disease/dementia. Coffee, tea, and caffeine consumption show promise in reducing the risk of cognitive decline and dementia. Individuals who consume one to 2 cups of coffee per day had a decreased incidence of mild cognitive impairment compared to non-drinkers.43 A 2015 Japanese study also found an inverse association between coffee consumption and dementia among women, nonsmokers, and those who do not drink alcohol.44 Most recently, a 2016 study, the Women’s Health Initiative Memory Study, looked at incident dementia rates in women >65 years of age with high vs low caffeine intake. Women with higher caffeine intake were less likely to develop dementia or any cognitive impairment compared with those consuming <64 mg/day.45
Type 2 diabetes. A 2009 prospective cohort study, which included 40,011 participants followed for more than 10 years, found that drinking at least 3 cups of coffee or tea was associated with a lowered risk of type 2 diabetes.46 A 2009 systematic review of 20 cohort studies showed that high intakes of coffee, decaffeinated coffee, and tea are associated with a reduced risk of diabetes.47
A meta-analysis of 12 studies involving 832,956 participants found an inverse relationship between cutaneous melanoma and coffee consumption.
Melanoma. A meta-analysis of 12 studies involving 832,956 participants demonstrated an inverse relationship between cutaneous melanoma and coffee consumption.47 The risk of melanoma decreased by 3% and 4% for one cup/day of total coffee and caffeinated coffee consumption, respectively. Furthermore, a 2016 meta-analysis found that caffeinated coffee may have greater chemopreventive effects against melanoma than decaffeinated coffee.48
Adverse effects
Despite the many potential benefits of coffee, caffeine is a potent drug that should be used with caution.49 People with underlying heart problems should avoid caffeine due to concern that it may cause palpitations from tachycardia. It may worsen anxiety problems or depression. Coffee may increase the production of stomach acids, which can worsen acid reflux or stomach ulcers.
Regular coffee intake is associated with a lower risk of mortality, reduced CV events, and a reduction in liver disease progression.
Caffeine is a potent diuretic and may decrease absorption of calcium and cause OA. Caffeine may cause dependence and withdrawal symptoms. Some of the symptoms of withdrawal include drowsiness, headaches, irritability, nausea, and vomiting. It may disrupt sleeping patterns by causing jitters and sleeplessness.49 Additionally, large amounts of caffeine may cause overdose and death.
The bottom line
Regular coffee intake is associated with a lower risk of mortality, reduced cardiovascular events, and a reduction in liver disease progression. Coffee may also have some utility for improving cognitive function and reducing the risk of type 2 diabetes. Caffeinated coffee should be limited to no more than 32 oz per day, due to the risk of insomnia, palpitations, anxiety, and gastritis.
