Health Benefits of Coffee: What Patients and Providers Should Know

How did we get here?

Every morning, most Americans do something that has been a staple in their respective routines for as long as they can remember. This is not showering, teeth brushing, nor breakfast eating, it is coffee drinking. Whether it helps the sleep deprived get through the day or it's simply an addiction being satisfied, many individuals demand their daily cup/s of Joe.

Coffee is believed to date back to 9th century Ethiopia, with the name derived from Kaffa, a region in Ethiopia where it originated. Since then, its popularity has increasingly grown, as well as our understanding of the science behind coffee and its effect on human health. The most notable active ingredient in coffee is caffeine, which is widely known for its stimulant and diuretic effects. However, we now understand that coffee is pharmacologically complex and contains many active compounds with potential health effects, including various antioxidants and diterpenes.

Caffeine chemically resembles adenosine, a molecule that generates a relaxing, drowsy effect, and is able to bind to adenosine receptors in the brain. This is largely why caffeine induces feelings of alertness, focus, and sociability. With chronic consumption of coffee, the brain will try to upregulate levels of adenosine to compensate for the receptors occupied by caffeine. This mechanism is responsible for individuals developing coffee tolerance and withdrawal. With increased levels of adenosine able to bind to their receptors, withdrawal symptoms can include drowsiness, low energy, and depressed mood. Caffeine also causes vasoconstriction in the brain. Coffee discontinuation results in increased blood flow to the brain, which can cause withdrawal headaches.

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It has been long assumed that, because caffeine acutely increases blood pressure (BP) and heart rate (HR), it may contribute to hypertension (HTN), arrhythmias, or other types of cardiovascular disease (CVD). This public perception is primarily based on anecdotal accounts and extends to the medical community, with many healthcare providers recommending limited caffeine intake for certain patient demographics.

Atrial fibrillation (AFib) is the most common type of treated arrhythmia with the potential to cause blood clots, stroke, heart failure (HF) and other heart-related complications. Between 2.7 and 6.1 million Americans are living with AFib, which results in over 750,000 hospitalizations, 130,000 deaths, and $6 billion in healthcare costs annually. Many risk factors have been identified for AFib, including high BP, diabetes, and HF. However, there is limited data available regarding association between coffee or caffeine and AFib.

About 45% of US adults have HTN. Most patients with HTN are asymptomatic, but if left untreated, are at risk for heart attack, stroke and other types of cardiovascular disease. High BP costs the US about $131 billion annually and in 2017 was associated with nearly half a million deaths.

Emerging coffee research

Extensive research over the past decade suggests that many widely held beliefs regarding coffee may not be evidence-based. A 2018 systematic review published in the Journal of Human Hypertension conducted a meta-analysis of all cohort studies investigating the association between coffee consumption and HTN. With a total of 243,869 individuals and 58,094 incident cases of hypertension, the study found an inverse association with coffee and HTN risk in a dose-response manner. Furthermore, risk was reduced by 2% with each additional cup of coffee/day and when compared to no coffee intake, risk was reduced by 3%, 5%, 8%, and 10% for 2, 4, 6, and 8 cups/day, respectively.

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A 2019 prospective study published in the Journal of the American Heart Association assessed incidence of AFib in US male physicians with differences in coffee consumption. A total of 18,960 participants were included with a mean age of 66 years old. Primary analysis showed a lower risk of AFib among physicians with reported consumption of 1-3 cups/day and no association between AFib and other levels of coffee intake. Furthermore, risk of AFib was reduced by 15% and 14% in males who drank 1 cup/day and 2-3 cups/day, respectively. Following this study, a systematic review published in the European Journal of Preventive Cardiology conducted a meta-analysis of studies assessing effect of coffee or caffeine consumption on new-onset AFib. Analysis of 361,143 individuals found no significant association between caffeine/coffee consumption and incidence of AFib. These results are consistent with previous meta-analyses of coffee or caffeine consumption and AFib.

A 2014 systematic review published in Diabetes Care conducted a meta-analysis of prospective studies investigating association between coffee consumption and risk of type 2 diabetes (T2D). With 1,109,272 participants and 45,335 cases of T2D, they found that coffee consumption was inversely associated with risk of T2D in a dose-response manner. Furthermore, T2D risk was reduced by 9% with each additional cup of caffeinated coffee/day and 6% with each additional cup of decaffeinated coffee/day. When compared to non-drinkers, coffee consumption reduced T2D risk by 8%, 15%, 21%, 25%, 29%, 33% in 1-6 cups/day, respectively. One mechanism for coffee's T2D-protective effects are from active coffee compounds including chlorogenic acid and trigonelline, which have shown to improve blood glucose metabolism and insulin sensitivity.

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A 2016 systematic review published in the European Journal of Epidemiology conducted a meta-analysis of prospective studies evaluating association between coffee intake and risk of mortality. The review included a total of 31 studies comprising 1,610,543 individuals and 183,991 cases of all-cause, 34,574 of CVD, and 40,991 of cancer mortality. Analysis showed an inverse association between all-cause and CVD mortality and coffee consumption in a dose-response manner. Furthermore, when compared with no coffee consumption, 4 cups/day reduced risk of all-cause and CVD mortality by 16% and 17%, respectively. No difference was found in coffee associated risk reduction between smokers and non-smokers for all-cause and CVD mortality. However, for cancer mortality, only non-smokers had a significant risk reduction, which was 10% when comparing 4 cups/day to none.

While many of these studies suggest health benefits of coffee, there are certainly negative or adverse effects that have been revealed in the literature. A 2012 systematic review published in the European Journal of Clinical Nutrition conducted a meta-analysis of randomized controlled trials assessing the effect of coffee on serum lipid levels. Analysis of 12 studies with a total of 1,017 individuals showed an association between total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and coffee consumption. This effect was found to be more pronounced in patients with hyperlipidemia, older age, and those who drank coffee unfiltered and/or in greater quantities. Furthermore, drinking coffee for an average of 45 days consecutively was associated with increases of 8.1, 5.4, and 12.6 mg/dl to TC, LDL-C, and TG, respectively. One likely mechanism for this is the diterpenes, cafestol and kahweol, which naturally occur in coffee and are believed to increase serum lipid levels.

What do our guidelines say?

The Dietary Guidelines For Americans defines moderate coffee consumption as 3-5 cups/day or up to 400 mg of caffeine per day. They state that this amount of coffee can be incorporated into healthy eating patterns and that moderate consumption is not associated with increased risk of major chronic diseases, such as cancer, cardiovascular disease (CVD), or death. On average, a single cup of coffee contains about 100 mg of caffeine. Recent studies show that the average American consumes below moderate caffeine levels, at about 165 mg per day.

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The American Diabetes Association (ADA) guidelines don't make any recommendation in regards to coffee or caffeine consumption. However, they state that higher intake of coffee is associated with reduced diabetes risk. The American College of Cardiology/American Heart Association (ACC/AHA) guidelines for prevention, detection, evaluation, and management of BP in adults states that coffee consumption in patients with hypertension is associated with acute increases in BP. However, they note that long-term use of coffee is not associated with increased BP or CVD. The ACC/AHA guidelines for management of AFib, ventricular arrhythmia, and blood cholesterol do not address the role of coffee or caffeinated beverages in these disease states.

Key coffee takeaways

We know that caffeine and by association coffee are physically addictive substances. This means that with chronic coffee consumption comes the baggage of caffeine withdrawal in the absence of continuous intake. While coffee temporarily increases BP and HR, this has not been associated with any serious health outcomes. Long-term coffee consumption has shown to elevate serum lipid levels, but has also shown to decrease risk for HTN, T2D, and even death. Our most respected medical guidelines unanimously approve of moderate coffee consumption, even in patients with or at risk for HTN, arrhythmia, or other types of CVD. There is a need for more research on the efficacy and safety of coffee in healthy individuals, as well as those with various health conditions.

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We must continue to pursue the truth about coffee and break away from perceptions which are medically unfounded. Given that the majority of the world consumes it on a daily basis, it feels reasonable that clinical coffee research should be a priority, especially with recent findings suggesting that it can help prevent some of the most common chronic diseases. Perhaps we will live in a future where healthcare providers are recommending coffee... crazier things have happened.