Coffee, a staple beverage of American culture and cultures around the world, remains the most ubiquitously consumed psychoactive agent on earth. However, coffee and caffeine can be shrouded in misinformation and confusion. One day you may meet someone trying to cut down on their coffee consumption, and another day, meet someone determined to increase their daily intake. So, what does the evidence say? We will evaluate both the costs and benefits of drinking coffee and outline what we believe is the ideal way to drink it to maximize its upside.
Focus– Caffeine’s stimulant effect is partially from its similarity to the molecule adenosine. Adenosine is a molecule in the body important for a variety of functions but also builds up in the brain over the course of the day. As its levels increase, a person becomes more tired generating the “sleep pressure” we need to close our eyes at night. By blocking the adenosine receptor, caffeine prevents drowsiness and fatigue. These benefits, however, are optimized in a person naïve to caffeine or a person drinking more caffeine than their baseline tolerance. Alternatively, if a person abstains from caffeine for a period of time, they may find its cognitive benefits more effective when consumption is resumed. Michael Pollan, one of the most accessible and authoritative writers on food and nutrition, recently published an audiobook on caffeine in which he fasts from it for three months. In the book, Pollan discusses the intense experience he had drinking caffeine after abstaining for an extended period and recommends people take short breaks from caffeine so they can completely capture its improvement in focus. Pollan asserts that most people drink caffeine daily not to help them focus, but to prevent caffeine withdrawal. He postulates that the brain fog many people experience in the morning is the body’s way of begging for its caffeine fix. Alternatively, if a person cycles their caffeine intake and intermittently deprives themselves of it, they will build up less tolerance and be more sensitive to its beneficial effects.
Weight loss– There is limited evidence that caffeine can help with weight loss and even reduce body fat by increasing a person’s basal metabolic rate. These effects, however, are limited by the fact that many caffeine-containing beverages are laced with another, more sinister compound: sugar. It goes without saying that a person’s caffeine consumption should be done with as little added sugar as tolerable to their palate.
Liver– There is robust evidence that caffeine protects the liver against fat deposition, liver fibrosis, and even liver cancer. Hepatologists (liver doctors) will often advise their patients to drink caffeine as a means of improving their liver health, and the evidence backs it up. Additionally, polyphenols and other components of coffee help with liver health and have anti-oxidant properties.
Cardiovascular– Though there is not enough evidence to conclusively say that coffee prevents heart disease (though there is some suggestion of it in limited data) it certainly does not put people at an increased risk of cardiovascular complications. Caffeine intake, in appropriate and moderate amounts, is safe for heart health and notably does not exacerbate atrial fibrillation.
The Potential Costs
Despite being consumed by nearly 85% of Americans on a daily basis, caffeine has side effects like any other drug. We will go into the potential costs of caffeine intake and how to minimize them.
Hypertension– The notion that caffeine causes hypertension is so ubiquitous that it almost seems intuitive. While it is physiologically true, large group data does not necessarily indict it as an independent cause of sustained high blood pressure. In studies that looked at pure caffeine intake, the increase in blood pressure is modest, about 4 mmHg on average. When coffee consumption was examined, the data was less clear. Some suggest that while caffeine independently raised blood pressure by increasing epinephrine in the bloodstream, other components in coffee bring it down. Overall, caffeine consumption does not seem to be a large risk factor for hypertension, but a patient struggling to keep their blood pressure under control would only benefit from moderating their intake.
Sleep– As we mentioned previously, Caffeine works by blocking adenosine receptors, inhibiting drowsiness and makes a person more alert and focused. While this can be beneficial for someone looking for optimized cognitive performance in the morning, you can see the conflict it could create as bedtime approaches. According to a study in Sleep Medicine Review, caffeine increases the time it takes to fall asleep, decreases the time a person is asleep and decreases the quality of sleep. During his three-months without caffeine, Michael Pollan endorsed a significant improvement in both the length and quality of this sleep. The negative impact of caffeine on sleep can be mitigated, and we will discuss that below in our ideal caffeine consumption plan.
Pregnancy– While the data on pregnancy and caffeine intake is both mixed and not entirely clear, there is some suggestion that caffeine intake correlates with lower birth weight. Lower birth weights are considered a harbinger of negative health outcomes. The American College of Obstetrics and Gynecology recommends moderate caffeine consumptions of under 200mg per day for pregnant patients. Exercising caution would be most prudent in this patient population. For expectant mothers who want to drink caffeine in moderation, we describe how to calculate caffeine intake below.
Hyperlipidemia– Unfiltered coffee, such as coffee made in a French press or Moka pot, increases LDL cholesterol, also known as the bad cholesterol when consumed in high amounts. LDL is correlated with an increased risk of heart disease. Most coffee purchased from a typical coffee shop or even instant coffee are run through a filter first and do not carry this risk. The filtering process is believed to remove some of the coffee’s natural oils, which are responsible for the cholesterol bump. Unfiltered coffee consumption should be limited.
How to do it best
Overall, coffee is an enjoyable beverage that has many benefits and some potential costs. Caffeine is a drug, and a person should be cognizant and deliberate about their caffeine intake. A person needs to consider how much caffeine is right for them, when they should drink it, and how often.
“Dosing” your caffeine– The ideal caffeine dose is different for every person. Caffeine is mostly processed by an enzyme in the liver called Cytochrome P450, Isozyme 1A2. There are, however, variants of this enzyme that can make people slow, intermediate, or fast metabolizers. In the absence of easily accessible genetic testing, the best way to know how quickly someone clears their caffeine is based on their own personal experience. Someone who can sleep right after a cup of coffee is likely a fast metabolizer while someone who feels jittery after half a cup is likely a slow metabolizer. Various levels of tolerance complicate this, however, some data suggest that fast metabolizers will naturally drink more coffee while their slow metabolizer counterparts will drink less. Broadly speaking, moderate caffeine consumption is about 50mg-400mg a day, but each individual’s moderate amount will be different. Once a person has a general sense of what their ideal caffeine intake is, they can look up common beverages at https://www.caffeineinformer.com/. This website is an excellent tool and has a variety of calculators a person can use to figure out how much caffeine is right for them.
Timing– While the amount of caffeine a person should drink is different based on the individual; the timing of caffeine intake follows more general principles. Broadly speaking, in order to avoid interference with sleep, people should drink caffeine earlier in the day. The half-life of caffeine in the bloodstream is 3-4 hours (dependent on the type of Isozyme 1A2 you have), so caffeine consumed in the evening will still have an impact at bedtime. Ideally, caffeine should be consumed well before a person plans to go to bed and at a time when they will benefit from its positive cognitive effects.
Cycling intake– As Michael Pollan vividly describes in his audiobook, caffeine withdrawal is both intense and can last 2-9 days. Outside of the common “caffeine headache,” withdrawal symptoms can include fatigue, mind fog, and even flu-like symptoms. With daily caffeine intake at high doses, most people are chasing away withdrawal rather than benefitting from the zoned-in feeling coffee can give you. By cycling caffeine intake, either by taking days off, or including days with a low caffeine beverage, a person’s caffeine can pack more of a punch on the days they choose to drink it.
And, of course…all caffeine should be consumed without sugar or with as little added sugar as possible! Any caffeinated beverage packed with sugar goes from a likely beneficial drink to a certainly harmful one.
Pollan M. Caffeine: How Caffeine Created the Modern World. In: Audible Originals; 2019.
Nehlig A. Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption. Pharmacol Rev. 2018;70(2):384-411.
van Dam RM, Hu FB, Willett WC. Coffee, Caffeine, and Health. N Engl J Med. 2020;383(4):369-378.
Clark I, Landolt HP. Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep Med Rev. 2017;31:70-78.
Internal Medicine-Pediatrics resident at the University of Chicago and aspiring Gastroenterologist.