A study published in JAMA in February found that drinking two to three cups of coffee daily was associated with a lower risk of dementia. Coffee is a daily habit for 66% of American adults and serves as a major source of disease-fighting nutrients for millions of Americans daily.

Studies suggest that coffee can boost mental and physical performance. Coffee consumption is linked to a reduced risk of heart disease, heart attack, and stroke, as well as a lower risk of cancers, including breast cancer, colorectal cancer, and liver cancer.

Coffee consumption is also linked to improved insulin sensitivity and a lower risk of diabetes, along with better mood and fewer symptoms of depression. Coffee molecules interact with brain receptors associated with alertness, attention, and memory and support healthy blood flow in the brain and body.

Caffeine is a stimulant that increases metabolism and reduces inflammation. Coffee is a rich source of polyphenols, plant-based compounds that help protect cells from damage, and contains chlorogenic acid, a polyphenol associated with antioxidant defense.

Studies suggest chlorogenic acid defends against inflammation, cell damage, and metabolic dysfunction. Coffee provides a small dose of fiber, which is a nutrient important for gut health.

"Caffeine is one of the most powerful and one of the most consistent tools that we have for performance," said Tom Coughlin, a sports nutritionist. Ninety-five percent of the athletes Coughlin works with include some form of caffeine in their performance strategy.

Caffeine speeds up reaction time and improves endurance, stamina, and strength. "It's part of their strategy in terms of optimizing performance, making the brain work better, and making the body work better," Coughlin said.

"High doses of antioxidants can be very beneficial for us across loads of different areas within the body," Coughlin said.

"Coffee helps feed the brain with the aroma, the taste, and the moment," said Agenor Limon, a professor of neurology. "If we're very rushed and distracted, we don't focus on things. That's a problem later in life," he said.

"I don't think that's the rescue for an unhealthy diet. Not one single food nutrient or beverage could save us," said Fang Fang Zhang, an epidemiologist and professor.

A daily intake of over 400 milligrams of caffeine—about three cups of coffee—can cause symptoms such as indigestion, jitters, anxiety, rapid heart rate, and headaches. Decaffeinated coffee is not linked to the same health benefits as regular coffee.