Originally appeared in the article, "Gut Check: Is Coffee Good for Your Gut Microbiome?" by Ashley Welch in Everyday Health on August 17, 2022.
Most people think of coffee as a quick energy boost or as part of their morning ritual to start their day, but research suggests a cup of joe can do much more than that.
Studies have found drinking coffee comes with a number of health benefits. “Moderate coffee consumption may reduce the risk of chronic diseases such as metabolic syndrome, obesity, type 2 diabetes, cardiovascular diseases, or some types of cancer,” says Lisa Ganjhu, DO, gastroenterologist and clinical associate professor of medicine at NYU Langone Health in New York City.
But did you know coffee may be beneficial to the gut microbiome, the trillions of bacteria, fungi, and viruses that live in the digestive tract and impact our overall health?
Here’s a look at what the research says about the potential positive effects of coffee on gut health and exactly how you can reap the benefits.
A Closer Look at the Health Benefits of Coffee
Scientists around the world have been studying the health effects of coffee for decades, and many have found positive results.
A study published in July 2022 in the Annals of Internal Medicine, for example, found that coffee consumption was linked to a lower risk of noncancer and cancer-related deaths.
Another study, published in June 2021 in the journal BMC Public Health, looked at the coffee habits of nearly 500,000 people and found that drinking java significantly lowers the risk of chronic liver disease.
Still, other research has linked coffee intake to a lower risk of obesity, metabolic syndrome, and type 2 diabetes.
“So the question is, these are all very different diseases with different pathways of development, so what can link these together?” asks Ali Rezaie, MD, the medical director of GI motility at Cedars-Sinai in Los Angeles. “One answer is potentially the gut microbiome.”
Coffee and Gut Health: What the Research Says
In recent years, researchers have been discovering more ways that the gut microbiome impacts our health.
The microbiome is made up of bacteria that is both potentially helpful and harmful to our health. When a body is healthy, both types of microbes coexist without any issues. But if there is a disturbance to this balance, the harmful bacteria can make us more prone to illness and disease.
“What's important to understand is that these microbes constantly communicate with each other, and what they produce affects us and what we do affects them, including what we eat and drink,” Dr. Rezaie says. “And more and more, we're understanding that the health and balance of the gut microbiome also affects health and disease.”
One area of research in this field is coffee’s potential effect on the microbiome.
A small study published in May 2020 in the journal Nutrients, for example, found that regular coffee consumption is associated with changes in some intestinal microbiota groups in which dietary polyphenol and caffeine may play a role.
Another small abstract of 34 people presented at the American College of Gastroenterology annual meeting in 2019 determined that the microbiomes of regular coffee drinkers were significantly healthier than participants who drank little or no coffee.
Scientists are working to understand the potential mechanisms for the perceived benefits of coffee on the gut, but there are some theories.
One has to do with coffee’s role as a stimulant. “Coffee gets the gut moving, and if you ask a lot of people, it makes them go to the bathroom,” Rezaie says. “Whenever there is a stimulant in the gut, that movement of the gut does change the microbiome generally in the right direction.”
He likens it to a stream of water. “If the water flow is nice and continuous, the water stays clear and even drinkable,” Rezaie says. “But if the stream becomes stagnant, then bacteria starts to grow and overpopulate.”
In the gut, this can lead to bacterial overgrowth, which can cause illness and disorders like irritable bowel syndrome. “So one potentially beneficial effect that coffee has is helping the stream move along,” Rezaie says.
Coffee also contains phytochemicals that are helpful to the gut and promote the growth of good bacteria, he notes.
While the research is still preliminary, Rezaie says it’s important to watch.
“This is where the research is going and potentially it's possible that the past beneficial effects of coffee for all these studies that we see is exerted, at least in part, through gut microbiome,” he says.
How to Reap the Health Benefits of Coffee
When it comes to coffee, how much you drink and what you put in it can play a role in its effects.
The maximum daily recommendation of caffeine is 400 milligrams, according to the U.S. Food and Drug Administration. That’s equivalent to about four cups of coffee.
At the same time, Rezaie notes that studies have shown that the optimal benefit of coffee is seen at around two to three cups per day. “Beyond that, it starts to wear off, so generally, that’s what I recommend,” he says. “But if you want to have just one cup in the morning, that’s fine, too. I wouldn’t go beyond four because it is a stimulant and can affect the sleep cycle.”
For this reason, he also recommends stopping caffeine intake around eight to nine hours before bedtime.
Of course, some people should avoid caffeine altogether.
“Those with conditions that are exacerbated by caffeine should avoid coffee,” Dr. Ganjhu says. “Also those sensitive to caffeine or those who get uncomfortable with coffee-induced jitters.”
For those who tolerate coffee well, it’s important to be aware of what you’re adding to it. Rezaie says if you prefer your coffee with milk and sugar, that is generally fine, though he advises limiting sugar to 1 to 2 teaspoons max.
“That’s about 4 grams of sugar,” he notes, “and in comparison, a caramel macchiato has about 16 grams of sugar. So obviously if you’re drinking a beverage that high in sugar, you’re defeating the purpose and negating any beneficial effects.”
Finally, in terms of preparation, research suggests there is really no difference when it comes to health benefits and how your coffee is made.
“It looks like it's quite universal in studies, meaning that instant coffee, drip coffee, or filtered coffee, they all appear to have beneficial effects,” Rezaie says. “So just drink it up, whichever way you like.”