Consuming two to three cups of coffee daily can bring a range of surprising health benefits. Although many drink coffee for a boost of energy, the beverage has a wide spectrum of effects on the body. Coffee is one of the most thoroughly studied drinks in the world, and researchers have conducted thousands of studies regarding its impact on life expectancy, cardiovascular health, blood sugar levels, weight loss, and cancer risk.
Composition and Early Concerns
Coffee contains over a thousand chemical compounds, including magnesium, potassium, niacin, and other B vitamins. In the past, scientists suspected that coffee could be harmful to health. In 1991, the World Health Organization classified coffee as 'possibly' carcinogenic due to links with bladder cancer, and other studies indicated a possible increased risk of lung cancer.
Revisiting Scientific Data
It later became clear that in some cases, scientists confused correlation with causation, as smokers often consume a lot of coffee. After accounting for this factor, the link between coffee and lung and bladder cancers virtually disappeared. Over the decades, hundreds of studies have changed the perception of coffee, showing that it may have a protective effect against a number of serious diseases, including certain types of cancer. When studying the components of coffee, it was found that many of them possess anti-inflammatory and anti-cancer properties.
General Conclusions on Benefits
A large meta-analysis summarizing decades of research across 67 health indicators concluded that for most adults, daily coffee consumption is 'more beneficial than harmful.' On average, the analysis showed that people who drink several cups of coffee a day have nearly 20% lower probability of premature death compared to those who drink little or no coffee.
Benefits for Liver and Heart
One of the most consistent findings after decades of coffee research is its positive impact on the liver. Rob van Dam, a professor at the Milken Institute of Public Health at Georgetown University, noted that coffee consumers show lower rates of liver cancer, non-alcoholic fatty liver disease, liver cirrhosis, and other liver diseases. Coffee consumption is also associated with lower liver enzyme levels, which usually indicates good liver health and lack of stress.
Van Dam, who specializes in nutrition, reported that the protective effects of coffee for the liver have been demonstrated in large observational, experimental studies, animal studies, and clinical trials. For example, a study published in 2021 tracked almost half a million adults for about 11 years and found that coffee lovers had a 21% lower risk of developing chronic liver disease and a 49% lower probability of dying from such a disease compared to non-coffee drinkers. These results were observed in people consuming any type of coffee, including espresso, instant, and decaf, with the risk reduction being associated with consuming just one cup a day, although the greatest benefit was seen with consuming three to four cups a day.
Protection Against Type 2 Diabetes
Coffee's ability to improve insulin sensitivity also explains why researchers found that coffee consumers suffer less from type 2 diabetes. Many large studies have shown that people who drink three to four cups of coffee daily have approximately 25% lower risk of this disease compared to those who drink little or no coffee. In fact, the probability of developing diabetes decreases by about 6% for every cup of coffee consumed daily (up to six cups).
This effect was identified in dozens of studies involving over a million people from Europe, North America, and Asia. It was observed in both men and women, young and old, smokers and non-smokers, and obese and non-obese individuals. Researchers also established that the risk changes depending on changes in coffee consumption. In studies tracking thousands of men and women over two decades, scientists found that increasing coffee consumption by one or two additional cups per day reduced the risk of type 2 diabetes by 11%. However, decreasing consumption by a similar amount increased the probability of developing diabetes by 17%. This effect was not observed when analyzing changes in tea consumption.
Role of Polyphenols and Parkinson's
Coffee is a rich source of polyphenols—compounds found in fruits, vegetables, whole grains, and other plants known for their health benefits. Studies have shown that these polyphenols, including chlorogenic acid, improve insulin sensitivity and blood sugar control. They also help protect pancreatic beta cells, which produce insulin and play a key role in the development of type 2 diabetes, according to Hubert Kolb, a researcher at the West German Center for Diabetes and Health in Düsseldorf, who studies the effect of coffee on health.
One of the most surprising and consistent findings about coffee consumption is the reduced risk of developing Parkinson's disease. Scientists believe this is largely related to caffeine. A large meta-analysis of data from two dozen studies involving over a million people established that people who drank up to three cups of coffee a day had a 28% lower probability of developing Parkinson's disease compared to those who drank little or no coffee. Meanwhile, people who consumed up to two cups of tea a day had a 26% lower probability of developing this disease. Van Dam noted: 'Initially, people were skeptical, but this has been repeatedly confirmed study after study, that people who consume a lot of caffeine—whether from coffee or tea—have a lower risk of Parkinson's disease.'
Physical Activity and Coffee
Daily physical exercise is one of the best ways to maintain health, and coffee can contribute to increased activity. In a rigorous study published in the New England Journal of Medicine in 2023, scientists recruited 100 healthy men and women and equipped them with fitbits, heart rate monitors, and other devices to measure health metrics. Participants were tracked for two weeks, instructed to drink caffeinated coffee on some days and abstain from coffee on others.
Scientists found that on days when people drank coffee—usually consuming one to three cups—they walked 1,000 steps more. This is equivalent to walking about half a mile. Gregory M. Marcus, the study's author and a professor of medicine in the cardiology department at the University of California, San Francisco, stated that this significant increase in physical activity could be one reason why coffee consumption is generally linked to better health. He added: 'Adding a thousand steps a day has a significant impact on many health indicators.' Marcus and his colleagues noted in their study that an extra thousand steps a day is associated with a 6–15% reduction in mortality, which has a 'strikingly similar scale of benefit for mortality observed among coffee consumers.'
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