Coffee delivers the boost that many people need to start their day. Now, new research suggests this breakfast powerhouse may also provide some protection against COVID-19.
Consuming vegetables and having been breastfed might also reduce your COVID-19 risk, according to the new study from Northwestern University in Chicago. Conversely, processed meats may increase your susceptibility to the coronavirus. Other foods studied — including fruit, tea and red meat — had no impact.
"We know that COVID is an infectious disease, similar to pneumonia or other kinds of respiratory infections. We know that immunity plays an important role in our ability to combat some of these infectious diseases," said study co-author Marilyn Cornelis.
"I was interested in seeing how nutrition could play a role [in COVID-19] because we know that nutrition impacts immunity," added Cornelis, an associate professor of preventive medicine at Northwestern University School of Medicine.
Other research has focused on individual health issues in terms of COVID-19 infection, including the impact of conditions such as diabetes. Less attention has been given to modifiable risk factors, other than weight, Cornelis said.
For the study, the researchers used UK Biobank data to examine an association between dietary behaviors from 2006 to 2010 and COVID-19 infections from March through November 2020 in the same people. The investigators looked specifically at foods shown to affect the immune system in earlier human and animal studies.
The study included nearly 38,000 participants who had received a COVID-19 test. About 17% tested positive for the virus.
The team found that nutrition might confer a modest degree of protection.
For example, consuming one or more cups of coffee a day was associated with a 10% decrease in risk of COVID-19 when compared to consuming less than one cup daily. Consuming at least two-thirds of a serving of cooked or raw vegetables daily (excluding potatoes) was also linked with reduced risk.
However, even eating less than half a serving of processed meat daily — think hot dogs and deli meat — was associated with higher risk. Like coffee, being breastfed as an infant was associated with a 10% reduced risk.
Why these dietary factors might make a difference is not yet known, and it's important to note that the study cannot prove a direct cause-and-effect relationship.
The reason why coffee seems protective while tea is not could be the greater amount of caffeine in coffee, Cornelis suggested.
"Alternatively, it could be other constituents of coffee that are unique and make it distinct from tea. For example, tea is often rich in flavonoids. Whereas with coffee, it's more polyphenols, specifically chlorogenic acid, which is actually a relatively unique constituent of coffee," Cornelis said. "It has been implicated in other diseases not related to COVID-19 but might also be driving this relationship."
In a similar juxtaposition, red meat consumption did not appear to boost risk for contracting COVID-19, but processed meats did.
"The relationship may not necessarily be related to meats all, but it could be the actual processing of these foods. These are just hypotheses, but because COVID-19 is so new, obviously more research is needed," Cornelis said.
Consuming a lot of veggies appeared to be good, in terms of risk, she said, though whether specific vegetables with certain nutrient profiles make a bigger difference is unknown.
"Some of these findings, they just are indicators of good eating habits. I think it just speaks to the importance of good nutrition, not only for COVID-19, but just for overall health," Cornelis said.
Not a substitute for vaccine
Certainly, coffee and veggies are not substitutes for the COVID-19 vaccine and other recommended preventive measures, experts say.
The U.S. Centers for Disease Control and Prevention says everyone age 12 and older should get a vaccine. Vaccines are not yet available for younger children.
Dr. Karen Studer is program director for the preventive medicine residency program at Loma Linda University in California. She said the study findings are similar to the teachings of lifestyle medicine and the idea that food is medicine.
"The benefits of a whole food, plant-based diet — which is mostly fruits and vegetables and grains — will protect you from a lot of diseases. This is exciting because it looks like it's true for infectious disease such as COVID-19, too," Studer said.
Other studies have also found benefits in coffee, including increased longevity, Studer said.
Small lifestyle changes can have a big impact on health, Studer added. That might include giving up tobacco, alcohol or sugar-sweetened beverages. If nutrition is challenging, you could focus on other lifestyle changes, such as improving sleep or managing stress, she said.
"My advice to my patients is, the degree at which you want to see change happen is the degree you're going to have to change your behavior," Studer said. "Look for your low-hanging fruit and then do small steps and really try to make changes over time to benefit your health long-term."
The findings were published online recently in the journal Nutrients.