There Are So Many Health Studies on Coffee. Which One Should You Trust?

There's no shortage of studies that make contradictory claims on coffee's health benefits and risks.

While one study showed that that excessive coffee consumption could lead to dementia and stroke, others suggested the opposite. A more recent study conducted by Tianjin Medical University found that consuming two to three cups of coffee each day was linked to a 28% lower risk of dementia.

This new research is just one of many coffee-focused studies published this year. Other studies have claimed that coffee could reduce the risk of heart disease and even COVID-19.

Americans are drinking more coffee than ever. Around 62% of Americans drink coffee daily and the average drink consumes three cups a day, according to the National Coffee Association. With such a high demand for caffeine, it's no surprise that coffee is a huge focus of nutrition research.

But with all the coffee studies out there, how do you know which ones to trust?

Whitney Linsenmeyer, PhD, RD, LD, an assistant professor in nutrition and dietetics at Saint Louis University, told Verywell that coffee "has been has been integral to the food cultures of many countries dating back to the 15th century" and there's a strong interest in researching about this staple beverage.

Many nutritional studies are observational, rather than experimental, which means they show correlation but can't directly prove cause and effect. “They allow us to study dietary trends or patterns in large populations,” Linsenmeyer said.

Observational studies may link coffee with cognitive health based on reports of how often people drink coffee. While they're not as accurate as experimental studies, they can show that further research is needed to confirm an association.

Which Coffee Studies Can You Trust?

Observational studies can still be reliable, but it’s better to learn how to interpret the many different observational coffee studies out there.

Nurgül Fitzgerald, PhD, MS, RD, an associate professor of nutritional sciences at Rutgers University, told Verywell, that we can judge the strength of a study by laying out a few questions.

For instance, evaluate the study's authors to see if they're trained in a relevant field and if they're looking to gain any financial benefits from the study publication, Fitzgerald said. Studies published in peer-reviewed and respected journals are typically the most reliable.

She added that it's also important to consider the number of participants, how the researchers control for potential biases, and how reliable their measurement instruments are. Some of these limitations are often covered in the discussion section of the peer-reviewed publications.

Coffee studies are highlighted in the media all the time, Fitzgerald said, and it's important to think about all of the results together instead of focusing on an individual study.

"If the results of an observational study can be repeated in many different populations and under different conditions and over time, it gives a much greater level of confidence in the reliability of the results," she said.

So Is Coffee Good For Your Brain?

Sherri M. Cirignano, MS, RDN, LDN, an associate professor and chair with the department of family and community health sciences at Rutgers University, told Verywell that over the past few years, research has been showing that coffee may actually be beneficial to cognitive health.

The new findings from Tianjin Medical University contributed to this growing body of evidence by examining data from over 360,000 participants in the UK Biobank. Researchers pointed out that the antioxidant properties of caffeine may be beneficial to brain health.

But another study evaluating data from the same biobank warned that drinking six or more cups of coffee a day was associated with 53% higher odds of dementia.

These studies don't necessarily rule each other out. But they should be considered together, along with the other available research out there.

"Individuals should consider all studies as a piece of a large puzzle that cannot be completed without many pieces from many other studies included," Cirignano said.

Dietary recommendations emphasize caffeine intake rather than coffee itself, she added. This means the caffeine intake can come from soft drink, tea, or energy drinks.

The Food and Drugs Administration said that caffeine can be part of a healthy diet for most people. For most adults, drinking 400 milligrams a day—about four or five cups of coffee is generally not associated with any negative health effects.