Drinking Coffee and Eating Vegetables May Help Protect Against COVID-19

Your daily cup of morning coffee may actually keep you in good health. A new study finds that drinking coffee, as well as eating vegetables, may boost the immune system and lower the risk of contracting COVID-19.

Nutrition and immunology researchers at Northwestern Medicine analyzed data from almost 38,000 people, looking at correlations between their intake of products such as coffee, tea, vegetables, fruit, meat, and more, and the rate of COVID-19 infections.

They found that drinking at least one cup of coffee per day was associated with 10% less risk of contracting COVID-19, and so is eating vegetables every day.

Of course, one food cannot prevent infection entirely, but findings like this shine further light on how nutrition affects the immune system. According to the authors, this is the first longitudinal study analyzing how nutrition affects the prevention of COVID-19. It could also pave the way for digging deeper into how diets can affect people’s susceptibility to other viruses at large.

“I am an expert in nutrition and knowing that nutrition does play an impact in immunity, I was interested in seeing whether certain dietary factors would kind of offset the risk of COVID-19,” senior author Marilyn Cornelis, associate professor of preventive medicine at Northwestern University Feinberg School of Medicine, tells Verywell.

The study was published in June in the journal Nutrients.

Drinking Coffee and Eating Vegetables May Help

Cornelis’s team used data from the UK biobank for 37,988 participants, 17% of which had tested positive for COVID-19 between March and December 2020. They looked at their dietary habits between 2006 and 2010 and adjusted the data for exposure to the virus.

“That provided us kind of with an unbiased measure of dietary behavior,” Cornelis says. “Although the fact that the leg between the collection of diet and the pandemic is quite large might be a limitation, at the same time, it provides a kind of a habitual measure of diet, which usually is quite stable.”

They specifically looked for correlations between products which, according to prior research, may boost immunity like:

• Coffee
• Tea
• Vegetables
• Fruit
• Fatty fish
• Processed meat
• Red meat

They also looked at whether participants had been breastfed growing up because that too has been previously linked to stronger immune systems.

The scientists found that some foods are correlated with a higher risk of COVID-19 infection, and some are correlated with a lower one:

• Having one or more cups of coffee a day—compared to having none—was associated with about a 10% decrease in risk of contracting COVID-19.
• Having at least half a serving (cooked or raw) daily of veggies can also go a long way and is associated with a lower risk of infection by 12%.
• Having even as little as half a serving of processed meat per day was associated with a higher risk of COVID-19. 
• Having been breastfed as a baby reduced the risk by 9% compared to not having been breastfed. 

Why Might This Be the Case?

Exactly why these foods help ward off the virus is still unclear, but the researchers are starting to formulate hypotheses.

“For example, we didn't see anything with tea. And although you might think that coffee and tea are very similar because both of these beverages contain caffeine, coffee contains roughly twice the amount of caffeine as tea,” Cornelis says. “So if caffeine is driving the relationship that we're seeing between coffee and COVID-19, perhaps we didn't see with tea because it is just a very weak source of caffeine.”

Caffeine and polyphenols—an organic compound found in large quantities in coffee—contain anti-inflammatory properties which could benefit the immune system.

On the other hand, the research might simply be picking up on a generally healthy diet, or maybe some of these dietary factors correlate with other healthy habits that the researchers are not capturing through this data alone.

There is still no evidence that a specific food or beverage prevents COVID-19 infection, and getting vaccinated is still the most effective way to decrease infection rates worldwide. 

“A weakness of the study was its use of self-reported data, which was collected from 2006-2010,” Megan Meyer PhD, director of science communications at the International Food Information Council, tells Verywell. “Since diets change over time and the dietary data was collected from 2006 to 2010 and then correlated with infection rates from 2020, it’s highly unlikely that what was reported in the dietary questionnaires actually impacted infection rates 10 to 14 years later.” 

Meyer also points out that the study did not have information on other known risk factors for the virus such as social distancing behavior, work environment and face mask use, and more.

Similarly, the researchers on the study also raise questions about how long it takes diets to affect immune systems. They still aren't sure whether making tweaks to your nutritional habits can immediately boost your defense against viruses or if, instead, it might take a while.

“This is a very interesting correlation and makes you wonder what might be going on, but it is far from definitive,” William Li, MD, medical director of the Angiogenesis Foundation, and author of "Eat To Beat Disease," tells Verywell. “The coffee consumption pattern was documented years before the pandemic and many factors are linked to vulnerability to COVID. This just makes us think about why this would be and how to study it more rigorously.”

Still, this might be a good step in the right direction in helping people become aware of the importance of "food as medicine." More people are interested in eating to beat disease and preserve health, Li says. “Our immune system is very complicated and we are just scratching the surface in our understanding of the power of food," Li adds.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.