How Many Cups of Coffee Should You Drink a Day, According to Science
A study now in the news claims that people who drink two to three cups of coffee a day live longer than those who avoid coffee. So should we all drink two or three cups? Not necessary. Let’s see where these numbers come from.
Two or three cups for longevity, maybe.
This recent study is based on data from the British Biobank, where the median age is 58, slightly more than half of the participants are women, and approximately 95% are white . On average, the researchers could follow the participants for 12 years after they answered the question about how much coffee they drank.
If we look at death from all causes, people who drank two to three cups of coffee a day had the lowest risk, and this applies to whether they drank ground, instant, or decaffeinated coffee. For cardiovascular disease, those who drank one cup a day had the lowest risk, but for arrhythmia (irregular heartbeat), four to five cups were optimal. In the results of the arrhythmia study, decaffeinated coffee was not associated with a reduced risk.
However, the study has many limitations if you’re trying to use it to figure out how much coffee to drink. This group of middle-aged Britons may not represent the rest of the world very well; and it’s not like people randomly decide how much coffee to drink. Income, social class and perceived health risks can influence this choice, just to name a few (British people also tend to drink a lot of instant coffee and espresso , it turns out). The researchers also took the data people reported at face value and suggested that they drank the same amount of coffee over the years rather than constantly overestimating it.
Three to four cups for other health outcomes
A review published in the BMJ looked at dozens of previous studies on coffee and concluded that people who drink coffee have a lower risk of cardiovascular disease, including strokes, some cancers, and some liver and gastrointestinal diseases. The amount of coffee associated with risk reduction was often three to four cups per day.
The author of this analysis said that people should not start drinking coffee because of these findings, but if you already drink coffee, it “may be part of a healthy diet.”
One of the reasons it’s so hard to pinpoint what’s going on with coffee is that coffee contains hundreds of different biologically active compounds, and caffeine is just one of them. The chemical profile can also differ depending on which beans you start with and how you prepare your coffee.
But another reason is that these studies don’t randomly identify people who drink coffee or not; they usually just ask people how much coffee they already drink. If your doctor has told you to limit your caffeine intake, say because of your blood pressure, you will find that you do not drink coffee in the study. Thus, people who avoid coffee may have different health risk factors than people who drink a lot of it, and this is not necessarily reflected in the study.
“Robust randomized controlled trials are needed to understand whether observed associations are causal [i.e., coffee-induced],” the authors conclude.
Four cups or less to be safe
The U.S. Dietary Guidelines refer only to coffee consumption by non-pregnant adults: “For healthy adults, the FDA lists 400 milligrams of caffeine per day as an amount not usually associated with dangerous adverse effects.” (200 milligrams is the recommended limit during pregnancy .)
In other words, coffee is not so important for health that everyone is recommended to drink it. But it’s also not that dangerous to have a hard limit. Instead, they name the amount, which, in principle, is not bad. (Truly a huge amount of caffeine would probably be bad. This is a level that they say with confidence is not a huge amount.)
So how much is coffee? Most brewed hours of coffee contain somewhere around 100 milligrams per 8 fl oz. This varies greatly depending on the brand and style of brew. For example, a 14-ounce Dunkin coffee contains 210 milligrams; 16 ounce McDonald’s coffee contains 145. You can find caffeine in your favorite beverage at Caffeine Informer .
Before ordering, note that the recommendations also state that sweetened coffee drinks are a common source of added sugar to the diet. We should keep added sugars below 10% of total calories, or about 50 grams. Starbucks iced coffee – 20 grams; a caramel frappuccino has 54. On the other hand, black coffee has almost none.