- Coffee consumption reduces all-cause mortality and total mortality among populations.
- Coffee consumption—caffeinated or decaffeinated—reduces the risk of developing Alzheimer disease.
- Coffee reduces the risk of some cancers including breast and gastric cancers. It also reduces the risk of depression and suicide.
- Coffee consumption seems to generally benefit the liver.
- Coffee may increase the risk of some cancers such as lung and laryngeal.
There is a true paradigm shift occurring in medical science regarding the healthfulness of coffee and it based on solid research. Just as Thomas S. Kuhn describes in “The Structure of Scientific Revolutions,” the old medical views on coffee are simply being refuted and overturned to the degree that we must let them go entirely. Physicians must begin to see coffee in a patient-centric perspective.
See our brief review of the systematic review literature on coffee here.
For most patients, coffee consumption of either caffeinated or decaffeinated coffee will benefit their health. Coffee has been found in thousands of well-constructed studies to protect populations against all-cause mortality and total mortality. The specific diseases being presented include cardiovascular disease (CVD), Alzheimer disease and other neurologic diseases, a wide variety of cancers, depression, suicide, and others.
For patients who are at risk of laryngeal or lung cancer, and a small handful of gastric cancers, it may be beneficial to avoid coffee.
It’s time to talk with your patients about whether it is appropriate for them to drink coffee as part of an all-around healthy diet and lifestyle. Coffee consumption can be one of the most cost-effective preventive interventions in medicine. And it tastes good.
Data: Coffee Reduces Mortality
Circulation
The results of a very recent large meta-analysis of studies of coffee was published recently in Circulation. The researchers found that higher total consumption of coffee, caffeinated coffee, and decaffeinated coffee was associated with a lower risk of total mortality.
The researchers “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.”
“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,” they wrote.
The American Journal of Epidemiology
The results of a very large meta-analysis were published in The American Journal of Epidemiology. This was a multi-center study published as “Association of Coffee Consumption with Total and Cause-Specific Mortality in Three Large Prospective Cohorts.” It was published by a group led by researchers from the Department of Nutrition at Harvard School of Public Health.
This group appears to be the only one that has conducted and published a dose-response meta-analysis of prospective studies to examine the dose-response associations between coffee consumption and mortality from all causes, cardiovascular disease (CVD), and all cancers.
They examined pertinent studies published between 1966 and 2013, including only prospective studies in which investigators reported relative risks of mortality from all causes, CVD, and all cancers for 3 or more categories of coffee consumption. Results from individual studies were pooled using a random-effects model. In all, 21 studies including 121,915 deaths and 997,464 participants, met the inclusion criteria.
The researchers found “strong evidence of nonlinear associations between coffee consumption and mortality for all causes and CVD (P for nonlinearity < 0.001). The largest risk reductions were observed for 4 cups/day for all-cause mortality (16%, 95% confidence interval [CI]: 13, 18) and 3 cups/day for CVD mortality (21%, 95% CI: 16, 26).
“Coffee consumption was not associated with cancer mortality. Findings from this meta-analysis indicate that coffee consumption is inversely associated with all-cause and CVD mortality,” they wrote.
Public Health Nutrition
A single-center meta-analysis included 17 studies, 1,054,571 participants, and 131 212 death events from all causes.
The researchers found what they called a U-shaped dose-response relationship between coffee consumption and all-cause mortality (P for non-linearity <0.001). Compared with non/occasional coffee drinkers, the relative risks for all-cause mortality were 0.89 (95 % confidence interval [CI] 0.85, 0.93) for 1≤3, 0.87 (95 % CI 0.83, 0.91) for 3≤5 cups per day and 0.90 (95 % CI 0.87, 0.94) for ≥5 cups per day, and the relationship was more marked in females than in males.
“The present meta-analysis of prospective cohort studies indicated that light-to-moderate coffee intake is associated with a reduced risk of death from all causes, particularly in women,”s the researchers wrote.
New England Journal of Medicine
A 2012 study in the New England Journal of Medicine similarly found that drinking coffee was associated with decreased total and cause-specific mortality.
This group examined the association of coffee drinking with subsequent total and cause-specific mortality among 229,119 men and 173,141 women in the National Institutes of Health–AARP Diet and Health Study who were 50 to 71 years of age at baseline. Participants with cancer, heart disease, and stroke were excluded. Coffee consumption was assessed once at baseline.
“Inverse associations were observed for deaths due to heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections, but not for deaths due to cancer. Results were similar in subgroups, including persons who had never smoked and persons who reported very good to excellent health at baseline,” they wrote.
“In this large prospective study, coffee consumption was inversely associated with total and cause-specific mortality” the researchers concluded.
European Journal of Epidemiology
A meta-analysis of all appropriate prospective studies on the relation of coffee with mortality for all causes, all cancers, cardiovascular disease (CVD), coronary/ischemic heart disease (CHD/IHD) and stroke found clinically significantly lower risks among coffee drinkers.
The pooled relative risks (RRs) of all-cause mortality for the study-specific highest versus low (≤1 cup/day) coffee drinking categories were 0.88 (95% CI 0.84-0.93) based on all the 23 studies, and 0.87 (95% CI 0.82-0.93) for the 19 smoking adjusting studies. The combined RRs for CVD mortality were 0.89 (95 % CI 0.77-1.02, 17 smoking adjusting studies) for the highest versus low drinking and 0.98 (95 % CI 0.95-1.00, 16 studies) for the increment of 1 cup/day.
Compared with low drinking, the RRs for the highest consumption of coffee were 0.95 (95% CI 0.78-1.15, 12 smoking adjusting studies) for CHD/IHD; 0.95 (95 % CI 0.70-1.29, 6 studies) for stroke; and 1.03 (95 % CI 0.97-1.10, 10 studies) for all cancers. This meta-analysis provides quantitative evidence that coffee intake is inversely related to all cause and, probably, CVD mortality.
Disease-Specific Data
Liver Diseases
A report at the recent 2015 annual meeting of the American Society for the Study of Liver Diseases examined 1155 patients with hepatitis C or B infections, and non-alcoholic fatty liver disease (NAFLD). These patients were also receiving transient elastography assessments of liver stiffness during the time from May 2012 to November 2013.
Daily coffee consumption reported by 1125 individuals ranged from 0-20 cups, with a daily average of 1.3 cups; nearly 73% drank instant coffee. The results were reported by A Hodge and colleagues in poster 47 at the 2015 annual meeting of the AASLD, held here recently. You can find the entire abstract here.
The average liver stiffness for all the individuals studied was 8.4 on the Korean Society of Pathologists Scoring System (kPa). Multiple linear regression that took controlled for age, alcohol consumption, smoking, and weight. Individuals with HCV benefited from coffee consumption, with liver stiffness an average of 2 kPa lower for those that drank at least 2 cups of coffee a day compared to non-coffee drinkers.
In patients with NAFLD, consumption of ≥2 cups of coffee per day was associated with a decrease in liver stiffness (controlled attenuation parameter, CAP) of about 9% (23 dB/m) compared with non-coffee drinkers.
In a separate review article published in 2014 in Liver International, also examined the association of coffee consumption with liver disease. This systematic review of studies on the effects of coffee on liver associated laboratory tests, viral hepatitis, nonalcoholic fatty liver disease (NAFLD), cirrhosis and hepatocellular carcinoma (HCC) was performed.
Coffee consumption was associated with improved serum gamma glutamyltransferase, aspartate aminotransferase and alanine aminotransferase values in a dose dependent manner in individuals at risk for liver disease.
In chronic liver disease patients who consume coffee, a decreased risk of progression to cirrhosis, a lowered mortality rate in cirrhosis patients, and a lowered rate of HCC development were observed. In chronic hepatitis C patients, coffee was associated with improved virologic responses to antiviral therapy.
Moreover, coffee consumption was inversely related to the severity of steatohepatitis in patients with non-alcoholic fatty liver disease. Therefore, in patients with chronic liver disease, daily coffee consumption should be encouraged.”
Alzheimer Disease
A 2015 meta-analysis published in the Journal of Neurology, Neurosurgery & Psychiatry, found that, among many factors, coffee consumption was significantly protective against development of Alzheimer Disease.
“Among factors with relatively strong evidence (pooled population >5000) in our meta-analysis, we found grade I evidence for 4 medical exposures (estrogen, statin, antihypertensive medications and non-steroidal anti-inflammatory drugs therapy) as well as 4 dietary exposures (folate, vitamin E/C and coffee) as protective factors of [Alzheimer Disease].
Depression
A systematic review was conducted of observational studies reporting the odds ratios (ORs) or relative risks (RRs) and 95% confidence intervals (CI) of depression linked to coffee/tea/caffeine consumption.
Random-effects models, subgroup and dose-response analyses were performed. Twelve studies with 23 datasets were included in the meta-analysis, accounting for a total of 346,913 individuals and 8146 cases of depression.
Compared to individuals with lower coffee consumption, those with higher intakes had pooled RR of depression of 0.76 (95% CI: 0.64, 0.91). Dose-response effect suggests a non-linear J-shaped relation between coffee consumption and risk of depression with a peak of protective effect for 400 mL/d. A borderline non-significant association between tea consumption and risk of depression was found (RR 0.70, 95% CI: 0.48, 1.01) while significant results were found only for analysis of prospective studies regarding caffeine consumption (RR = 0.84, 95% CI: 0.75, 0.93).
“This study suggests a protective effect of coffee and, partially, of tea and caffeine on risk of depression,” the researchers wrote.
Prostate Cancer
In one study, all epidemiologic studies regarding coffee consumption and prostate cancer risk were included. Odds odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated to estimate the strength of the association.
The analysis included 12 case-control studies involving 7,909 prostate cancer cases and 9,461 controls and nine cohort studies involving 455,123 subjects. Compared with patients in category with the lowest consumption, patients in the unstratified highest category of coffee consumption showed a significance reduction in prostate cancer risk (OR 0.91, CI 0.86-0.97).
A borderline significant influence was also found when the stratified highest category (U.S. ≥ 4, Europe ≥ 5) of coffee consumption was compared with the reference category (OR 0.96, CI 0.92-1.00), but no relationships were observed for the other two categories.
In another analysis conducted by coffee consumption and prostate cancer stage and Gleason grade, our results showed a significant inverse association in all categories of prostate cancer except Gleason <7 grade in a fixed-effects model; the results remained the same, except for advanced prostate cancer, in a random-effects model.
"Our meta-analysis suggests that high (e.g., highest ≥ 4 or 5 cups/day) coffee consumption may not only be associated with a reduced risk of overall prostate cancer, but also inversely associated with fatal and high-grade prostate cancer." the team concluded.
