With millions drinking morning coffee to start the day, recent research has created a new buzz around caffeine consumption.

A large UK study from September found that moderate caffeine consumption from coffee or tea reduces the risk of developing multiple cardiometabolic diseases such as heart disease, stroke and diabetes. Another study, published in January, concluded that drinking coffee in the morning was particularly beneficial in reducing cardiovascular disease and premature death.

It's good to know what the evidence is for the health benefits of coffee? And what is the physiological basis for these benefits? How much coffee is good for most people, according to these studies - and how much is too much? Should some people be especially careful about drinking coffee? And if you don't like coffee, are there similar benefits from drinking tea or other beverages?

To help with these questions, I spoke with CNN health expert Dr. Leana Wen. Wen is an emergency room physician and associate professor at George Washington University. She was previously the health commissioner for Baltimore.

CNN: What is the evidence for the health benefits of coffee, and what is the physiological basis for these benefits?

Dr. Leana Wen: The evidence is quite strong. In addition to recent studies, a wealth of research over decades has found that moderate coffee consumption is associated with a reduced risk of developing numerous diseases, including heart disease, diabetes, some types of cancer, and even dementia.

It is not known exactly why this happens, although there are several hypotheses. For example, coffee contains chemicals that are thought to have antioxidant and anti-inflammatory properties, possibly contributing to its effect on reducing cancer risk.

Substances in coffee may help the body use insulin better and help control blood sugar. And some compounds may help better process cholesterol, possibly contributing to protection against negative outcomes. More research is needed to understand which components of coffee have beneficial health effects.

CNN: How much coffee is good for you?

Wen: Many of these studies found positive health effects at a moderate level of consumption, which is generally defined as two to four cups of coffee per day.

In a 2024 study in the United Kingdom, the risk of developing many new cardiometabolic diseases was reduced by over 48% for those who drank three cups of coffee per day compared to those who did not drink or drank less than one cup per day.

According to a large 2022 study, the greatest reduction in early mortality was seen for those who drank two to three cups of coffee per day. Interestingly, this study found that drinking ground coffee reduced the risk of early death the most (27%). Instant coffee had the least effect (11%).

Many studies have found positive health effects of coffee at a moderate level of consumption.

Many studies have found positive health effects of coffee at a moderate level of consumption. Halfpoint/iStockphoto/Getty Images

CNN: How much coffee is too much?

Wen: Coffee jitters are related to consuming too much caffeine, which can cause heart palpitations, anxiety, restlessness, and difficulty sleeping. According to the U.S. Food and Drug Administration, 400 milligrams of caffeine per day is safe for most adults. That's about the amount in four cups of coffee.

Many people exceed this amount and experience no ill effects. But people who have difficulty sleeping or other problems should be aware that these may be due to caffeine consumption.