Coffee is one of the most ubiquitously consumed beverages in the world. Globally, over 2.25 billion cups of coffee are consumed every day, and the average American drinks about 22 gallons of it annually. This means caffeine is the most widely used psychoactive substance on the planet.
Despite its widespread use, most people don’t know much about its effects. And what’s worse, we often hear contradictory information about its potential benefits and harms. So we set out to get some clarity on the topic by diving deep into this episode of Danny Lennon’s Sigma Nutrition podcast. (Sigma nutrition is a go-to resource for evidence-based approaches to nutrition and health).
The entire episode is dedicated to casting a light on the effects of coffee. Danny and his guest Alan Flanagan bring great clarity to the topic, drawing from their extensive knowledge of scientific studies on the topic and covering many health dimensions, including cardiovascular, neurological, cognitive, and performance.
Here are the key takeaways:
- Antioxidant effects of coffee.While we associate coffee with caffeine, it turns out that it is also a rich source of polyphenols. These are the natural compounds found in many plants (e.g., blueberries, cocoa) that are known to have significant antioxidant effects. They are associated with benefits for cardiovascular health, neurological health, and overall healthspan.
- Optimal consumption. When you look at the effects of coffee across different health dimensions (cardiovascular disease, diabetes, neurodegenerative diseases) there is a very consistent pattern in which the health benefits peak at similar amounts of coffee consumption. This “U” or “J” shaped curve of effect peaks at 2 to 4 cups per day, and drops at both lower and higher levels of consumption. The effects are also seen mostly in habitual (daily) consumers.
- Note that 2 to 4 cups is a pretty broad range given that: (1) different studies report different peaks in their curves; (2) the specific type of coffee consumed and the way it is prepared has an impact on its effects; and (3) serving sizes vary across studies. What is remarkable, is the fact that across so many studies looking at different health effects of coffee, the same “peak” effect is observed.
- Positive effects on cardiovascular disease and mortality rates. Across multiple long-term studies (5 to >20 years in duration), an overall reduction in mortality from cardiovascular disease among frequent consumers (i.e., people who drink 2 to 3 cups per day) is consistently observed
- Positive effects on brain health. Across studies using large cohorts over long periods of time, you also see a directionally consistent reduction in risk for Alzheimer’s disease and dementia. This risk reduction appears to be statistically significant, with drops in the 20%-30% range. The same effect was not observed in consumption of decaffeinated coffee.
- Effect on risk of Parkinson’s disease. Coffee’s neuroprotective effects show the strongest and most consistent impact on Parkinson’s. The studies on this disease show an observed relative risk reduction in the range of 30%-40%. This is attributed to the psycho-stimulation effect of caffeine itself. Caffeine has been shown to increase activity in the dopaminergic reward system, as well as increasing sympathetic activity in the brain.
- Protective effect against depression. A number of meta analyses also show relatively lower risk of depression in habitual coffee drinkers. One interesting observation is that the effect on depression may be attributed to the anti-inflammatory effects on the brain of the polyphenols in coffee.
- Negative effect on blood pressure. Coffee does appear to have a hypertensive effect. So it is not ideal to consume if you have hypertension. Interestingly, however, when you compare the effects from ingesting coffee to pure caffeine, the latter has a much more noticeable impact. The implication is that other compounds in the coffee work to soften the effect of the caffeine on blood pressure
- Coffee and cholesterol. Some studies have shown that coffee consumption can lead to increased LDL cholesterol and triglycerides. The nuance here is that the effect was observed in unfiltered coffee as opposed to the filtered kind. The filtration apparently catches the oils that contain the cholesterol-increasing compounds
- Upper limits of caffeine consumption. Per day, the maximum consumption of caffeine should be around 400mg. Consumption in the general population ranges from 80 to 400mg per day. One thing to keep in mind is that the caffeine content of coffee can vary greatly due to many factors, for instance how the beans are roasted and how the coffee is brewed.
- Coffee and sleep.Caffeine directly inhibits adenosine receptors in the brain, which prevents the buildup of adenosine that triggers the feeling of sleepiness. Keep in mind that the half-life of caffeine is about 6 hours, though this is influenced to some degree by metabolism and genetic variants that allow some people to process caffeine faster than others.
- Coffee and anxiety. Consuming very high levels of caffeine is known to trigger anxiety and jitteriness. This is exacerbated by genetic variations that can make people less tolerant to caffeine.
- Coffee and colorectal cancer. Some studies have shown an association between coffee consumption and lower incidence of certain cancers, such as colorectal cancer. This is thought to be related to the fact that coffee increases gastrointestinal motility and can stimulate bowel movement. Some people can be very sensitive to this effect and can develop irritable bowel syndrome.
There seem to be lots of good reasons to justify your daily coffee habit, as long as you don’t overdo it. So go enjoy your next cup!