New Health Benefits From Daily Coffee
By Jeffrey Huntington
Coffee is a widely consumed beverage.1-3 It contains over 1,000 compounds, many of which are biologically active. Coffee also contains a complex mixture of polyphenols, making it one of the most popular pharmacologically active beverages.1,4-11
Scientific interest in uncovering the health benefits contained in a daily cup of coffee has exploded in the last several years.
For example, drinking two extra cups of coffee daily may reduce your risk of developing type II diabetes. That’s the conclusion of a 2014 study of more than a million people, which demonstrated a 12% decrease in diabetes risk for each additional two cups of coffee consumed (the decrease was 11% among decaffeinated coffee drinkers).4
That’s only one example of the rapidly expanding literature regarding the benefits of drinking coffee. There now is compelling evidence of coffee’s health benefits regarding cardiovascular disease, metabolic syndrome, neurodegenerative disease, plus liver and kidney cancers.6,12-19
And a stunning epidemiological study has shown sharp reductions in the risk of overall death among coffee drinkers.5
Enjoying a cup of coffee—or more—provides important longevity and protective benefits.5,14
Coffee Reduces Risk Of Death
In a study funded by the National Institutes of Health and published in the prestigious New England Journal of Medicine, researchers explored the relationship between coffee drinking and the risk of dying. The study included more than 229,000 men and over 173,000 women who ranged in age from 50 to 71 years at the start of the study.5 The researchers followed the subjects for up to 13 years—or 5.15 million person-years!—making this one of the most powerful studies of its kind.
The researchers found that the risk of dying was significantly reduced in those who drank coffee (all levels of consumption) compared to those who did not.5 Compared to those who drank no coffee, the risk for men of dying from any cause was reduced 6% among those who drank1 cup/day, 10% for 2-3 cups, 12% for 4-5 cups, and10% for 6 or more cups/day. For women, the risk reduction was 5, 13, 16, and 15%, respectively.
While these findings are certainly impressive, the researchers also discovered that coffee consumption produced significant reductions in the risk of dying from a number of specific causes, including heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.5
It is evident from this study, and many earlier, smaller studies, that far from being “bad for you,” as was once believed, coffee can be considered an important promoter of long life and good health.
Coffee Provides Cardiovascular Protection
The complex mix of anti-inflammatory polyphenols and other bioactive compounds in coffee delivers potent cardioprotective properties. The greatest benefits have been found in filtered coffee consumption.20-23 Reversing earlier concerns that coffee might increase or aggravate cardiovascular disease risk, large epidemiologic studies reveal important positive effects on the heart, blood vessels, and brain that contribute to a reduction in the risk of heart disease, atherosclerosis, and stroke.21,24,25
In one large meta-analysis, over 1.2 million participants were evaluated for their cardiovascular disease risk according to their coffee consumption.12 Compared to subjects who drank no coffee at all, the researchers found a 15% cardiovascular disease risk reduction among those who drank an average of 3.5 cups/day, and 11% for those who had an average of 1.5 cups/day. This was an important study since it showed some level of protection for all amounts of coffee consumption.
One of the most important predictors of cardiovascular disease risk is endothelial dysfunction.26 The endothelium is an ultra-thin layer of cells that lines blood vessels. It sends biochemical signals, including nitric oxide, to smooth muscle cells in the vessel walls, triggering them to relax and dilate, or contract and constrict, thereby regulating blood flow and pressure throughout the body.27 People with atherosclerosis (hardening of the arteries) have perturbed endothelial function, causing vital organs such as the heart or brain to suffer from disrupted blood flow, which in turn can produce a heart attack or stroke.28
The effects of coffee consumption on endothelial function have been controversial, in part because of confusion regarding the role of caffeine. Caffeine has been found to temporarily worsen endothelial function in some studies, but the antioxidant and other benefits of polyphenols in coffee appear to largely negate this effect.1,15,29 In a group of older adults consuming a typical drink of boiled caffeinated coffee, endothelial function was 49% better in those who reported high consumption compared with those reporting low consumption.16
Even 200 mg of caffeine (equivalent to about 2.5 cups of coffee) improved endothelial function by 160% in patients with known coronary artery disease and by 121% in healthy volunteers, suggesting there may in fact be a beneficial role for caffeine in addition to the polyphenols.6 In a separate study, 300 mg of caffeine, given to healthy young men, produced a 25.5% improvement in endothelial function; this effect was traced to an increase in production of the vessel-dilating compound nitric oxide.30
Decaffeinated coffee has also repeatedly been shown to improve endothelial function, reducing the risk of cardiovascular disease. In one study, endothelial function improved 46% one hour after consumption of two cups of decaffeinated Italian espresso coffee, and by 23% one hour after consumption of one cup.31
Given that decaffeinated coffee exerts positive effects on endothelial function, it appears that the polyphenol compounds exert substantial benefits. A study of healthy, non-diabetic men showed that ingestion of a single dose of purified caffeine polyphenols improved endothelial function following a glucose challenge (simulating a meal).23 This is an important finding, given that after-meal increases in blood sugar are strongly associated with poor endothelial function and increased cardiovascular risk.32-34
Both caffeinated and decaffeinated coffee, even at fairly high levels of consumption, exert favorable effects on endothelial function and on cardiovascular disease risk. Importantly, one study showed no significant negative effects of coffee consumption, either caffeinated or decaf, on certain types of ECG associated with cardiovascular disease.35
Coffee Protects Against Metabolic Syndrome And Type II Diabetes
The modern lifestyle is contributing to an alarming and constant increase in the prevalence of obesity, type II diabetes, and their deadly long-term consequences.36-40
In particular, metabolic syndrome—abdominal obesity, hypertension, abnormal blood lipids, and insulin resistance producing borderline/high blood sugar levels—is on the rise, along with increased risks for diabetes, heart disease, cognitive decline, and even cancer.37,41,42
Fortunately, there’s a growing body of evidence favoring coffee consumption as a means of protection against both metabolic syndrome and diabetes.
In a study from Japan, where rates of metabolic syndrome have been rising sharply over the past decades, all components of metabolic syndrome occurred less frequently among coffee drinkers than among non-drinkers. More components of metabolic syndrome were present in those who drank less coffee.43
Other studies have shown similar effects, with heavy coffee drinkers being more protected from metabolic syndrome components like elevated triglycerides; one study showed that drinking 1.5 to nearly 3 cups/day offered a 49% reduction in the risk of having high blood sugar.13
Coffee’s impact on fat accumulation is also favorable. Both light (1-3 cups/day) and moderate (4 or more cups/day) coffee consumption was shown to reduce abdominal fat collections in a group of middle-aged men. Moderate coffee consumption was also associated with higher blood levels of the beneficial hormone adiponectin, which helps regulate metabolic processes, further evidence of reduced deleterious activity of fat tissue.14,44
Animal studies provide some insights into how coffee exerts its protective effects against metabolic syndrome.
In one study, rats were fed a diet rich in animal fats and sugars, including fructose. They rapidly developed metabolic syndrome, which led to dangerous remodeling of their heart structures and also to non-alcoholic fatty liver disease (NAFLD), both of which occur in humans who consume too much sugar and fat.45 But when a supplemental coffee extract was added to the rats’ diet, those unhealthy effects were significantly reduced, and the animals’ glucose tolerance and high blood pressure also resolved.45
Similarly, mice fed a high-fat diet gained weight and increased abdominal fat stores, but when fed the same diet and supplemented with coffee (decaf or regular) they had lower body weights and fat stores.46 The supplemented animals also had significantly lower levels of liver damage indicators and inflammatory markers, compared with unsupplemented controls.
Even in animals with both metabolic syndrome and diabetes, coffee has proved to be therapeutic. A study of rats that had both disorders showed coffee consumption reduced serum glucose, total cholesterol, and triglycerides, thus lowering risk factors for developing cardiovascular disease and other complications of metabolic syndrome.47
The benefits of coffee on metabolic syndrome were summarized in a comprehensive review in late 2013. Of the studies examined, all of the animal and most of the human research demonstrated protective effects of coffee on metabolic syndrome and on development of non-alcoholic fatty liver disease (the few human studies that showed no effect were conducted among young populations, who have a relatively low incidence of metabolic syndrome at baseline).48
A main risk posed by metabolic syndrome is the development of full-blown type II diabetes, the result of sustained exposure to fat-related inflammatory cytokines and poor insulin sensitivity.49 As with metabolic syndrome itself, coffee is highly protective against type II diabetes.
A large multi-ethnic study of more than 75,000 men and women showed that drinking 3 or more cups/day of regular coffee reduced risk of developing type II diabetes 35% in women, and 14% in men; this study did not find significant risk reduction with decaffeinated coffee.50
That difference between caffeinated and decaf coffees, however, seemed to disappear in research that examined even larger populations. Two important 2014 meta-analyses, each including more than a million participants, provide definitive evidence that both kinds of coffee offers protective effects against type II diabetes. The first demonstrated that compared with little or no consumption, the risk for developing diabetes was reduced by 8, 15, 21, 25, 29, and 33% for consumption of 1 to 6 cups/day (respectively), with protection seen for both caffeinated and decaffeinated brews.51
The second meta-analysis showed similar results. Compared with the lowest level of coffee intake, those drinking the largest amounts of regular coffee had a 29% lower risk, while those drinking the largest amount of decaf had a 21% lower risk.4 This study also demonstrated that each additional two cups of regular coffee reduced diabetes risk by 12% (11% in decaf drinkers).4
Animal studies show that coffee (decaf and regular) contributes to decreased insulin resistance (the precursor to type II diabetes) and reduces blood sugar levels by modulating several proteins involved in insulin signaling and down-regulating genes involved in inflammation.52 Subsequent research suggests these effects may in turn lead to increased energy utilization and energy expenditure, both important factors in reducing total body fat stores and reducing the risk for diabetes and metabolic syndrome.53
Coffee Protects Brain Cells
Both caffeine and coffee show powerful effects in protecting brain cells from age-related degeneration. Epidemiologic studies show that people with higher intakes of coffee and caffeine are less likely to develop Alzheimer’s or Parkinson’s diseases, two of the most feared cognitive disorders of aging.54-59
People with mild cognitive impairment (MCI, the precursor to Alzheimer’s) who have higher blood caffeine levels are significantly less likely to progress to full-blown dementia, and rates of cognitive decline are slower in people with higher caffeine intake.60,61 Coffee drinkers who consume 3 cups/day are 28% less likely to develop Parkinson’s disease.62
In animal studies, it has been shown that caffeine and caffeinated coffee can prevent Alzheimer’s-like cognitive impairment from developing as mice age, and reverse the cognitive impairment and accumulation of the abnormal Alzheimer’s brain protein called Abeta in aged mice.63 Caffeine also prevented the brain changes associated with Parkinson’s disease in an animal model, through reduction in inflammatory cytokines and preservation of brain cells in important memory regions.55,64
But that’s not the only beneficial component of caffeinated coffee. Studies have shown that caffeinated coffee elevates plasma levels of a growth factor (GCSF—or granulocyte-colony stimulating factor) that is associated with improved memory. GCSF is also thought to promote formation of new brain cells and the synapses that connect them.64 And a specific non-caffeine coffee component called EHT ( eicosanoyl-5-hydroxytryptamide) has direct anti-inflammatory and antioxidant effects that preserve the specific neurons that die off in Parkinson’s disease.58
Caffeine is also associated with a decreased risk of depression, as shown by studies documenting up to a 43% risk reduction in people with the highest versus the lowest caffeine consumption.65,66 Consumption of coffee itself provides a 39 to 77% reduction in risk of depression.66,67