Earlier this year, the Dietary Guidelines Advisory Committee (DGAC) released a report^[1] stating that up to five cups of coffee per day, or up to 400 mg of caffeine, is not associated with long-term health risks. Not only that, they highlighted observational evidence that coffee consumption is associated with reduced risk for several diseases, including type 2 diabetes, cardiovascular disease (CVD), and neurodegenerative disorders. The body of data suggesting that moderate coffee—and, in all likelihood, tea—consumption is not only safe but beneficial in a variety of mental and medical conditions is growing fast.

A substance known to increase blood pressure might actually be good for the cardiovascular system. Caffeine consumption can cause a short-lived increase in blood pressure, and regular use has been linked to a longer-term increase. However, when caffeine is ingested via coffee, enduring blood pressure elevations are small and cardiovascular risks may be balanced by protective properties. Coffee beans contain antioxidant compounds that reduce oxidation of low-density lipoprotein (LDL) cholesterol, and coffee consumption has been associated with reduced concentrations of inflammatory markers.  Moderate coffee intake is associated with a lower risk for coronary heart disease as far out as 10 years, and data suggest that an average of two cups per day protects against heart failure.  Finally, a study presented during a poster session at the Heart Rhythm Society 2015 Scientific Sessions counters the long-held dogma that patients with arrhythmias should avoid caffeine, finding no association between the compound and premature atrial or ventricular contractions.

According to a 2011 meta-analysis, consuming between one and six cups per day reportedly cut stroke risk by 17%.

Despite coffee's association with increased blood pressure, the steamy brew appears to confer benefit to other aspects of so-called "metabolic syndrome," the dangerous cluster of hypertension, hyperglycemia, abnormal lipid levels, and increased body fat. Numerous studies have linked regular coffee drinking with improved glucose metabolism, insulin secretion, and a significantly reduced risk for diabetes.

With so many foods thought to increase cancer risk—soda, alcohol, and grilled meats among them—at least we can rest easy when it comes to coffee according to recent data. Evidence suggests that moderate to heavy coffee consumption can reduce the risk for numerous cancers, including endometrial (> 4 cups/day), prostate (6 cups/day), head and neck (4 cups/day), basal cell carcinoma (> 3 cups/day), melanoma, and breast cancer (> 5 cups/day).

Beyond the short-term mental boost it provides, coffee also appears to benefit longer-term cognitive well-being. A 2012 study reported that patients with mild cognitive impairment and plasma caffeine levels of > 1200 ng/mL—courtesy of approximately three to five cups of coffee per day—avoided progression to dementia over the following 2-4 years.

A 2011 study suggests that a boost in coffee consumption might also benefit our mental health.  Women who drank two to three cups of coffee per day had a 15% decreased risk for depression compared with those who drank less than one cup per week. A 20% decreased risk was seen in those who drank four cups or more per day.

The liver might help break down coffee, but coffee might protect the liver in some cases. Evidence suggests that coffee consumption slows disease progression in patients with alcoholic cirrhosis and hepatitis C, and reduces the risk of developing liver carcinoma. A 2012 study reported that coffee intake is associated with a lower risk for nonalcoholic fatty liver disease, while work published in 2014 found that coffee protects against liver fibrosis in those with already fatty liver disease.

As is often the case, with benefits come risks, and coffee consumption certainly has negative medical and psychiatric effects to consider. Besides the aforementioned potential increase in blood pressure, coffee can incite or worsen anxiety, insomnia, and tremor and potentially elevate glaucoma risk.  Also, given the potential severity of symptoms, caffeine withdrawal syndrome is included as a diagnosis in the DSM-5.

Additional research is necessary to better assess and balance the potential benefits and drawbacks of coffee consumption. But mounting evidence suggests that going back for a second cup might not necessarily be a bad decision.

 Roger Knapp MD

different drinks and their caffeine.