Coffee Consumption as a Preventive Measure Against COVID-19 Infections, Depression

As decadent as café au lait may sound, the adding of milk to coffee enhances its already anti-inflammatory and antiviral effects.

Research has found that drinking one to two cups of coffee daily helps prevent COVID-19 infection. New Africa/Shutterstock

Daily moderate coffee consumption reduces the risk of cardiovascular diseases and cancer-related mortality, combats depression and anxiety, and aids the body in resisting COVID-19 infection, studies have found.

Winter is flu season, with a heightened prevalence of respiratory infections. Additionally, recent outbreaks of mycoplasma pneumonia in China, coupled with a resurgence in COVID-19 cases, have left people feeling uneasy.

Can we fight against bacterial invasion with simple daily dietary choices? Jin-Jian Zhang, emeritus professor at the National Taiwan University College of Medicine with years of research experience in coffee, shared on the “Health 1+1” program how daily coffee consumption can alleviate inflammation, enhance immunity, and reduce the risks of cardiovascular diseases and cancer.

The Potential Role of Coffee in Combating COVID-19

A study published in Cell & Bioscience in November 2023 found that drinking about one to two cups of coffee daily may be sufficient to inhibit infection by multiple variants of COVID-19.

The coffee used in the study was purchased from supermarkets and included ground coffee (from Laos, Honduras, Indonesia, Guatemala, and the United States), instant coffee (from Japan, Brazil, and Germany), and decaffeinated coffee (from Japan). All of the coffee types were confirmed to possess the ability to inhibit virus infection in cells. The research also found that adding milk or sugar doesn’t affect the beverage’s antiviral effect.

The study found that the protective mechanism of coffee against COVID-19 involves inhibiting the binding of the virus’s spike protein with human angiotensin-converting enzyme 2 (ACE2) and reducing the activity of transmembrane serine protease 2 (TMPRSS2) and cathepsin L (CTSL), thereby preventing the virus from infecting cells.

Another study conducted by the same research team, published in the International Journal of Biological Sciences in July 2022, found that extracts from Arabica coffee leaves, which share similar active components with coffee, can inhibit the entry of the COVID-19 virus and its variants into human cells.

The compounds associated with anti-COVID-19 activity in coffee leaf extracts, including chlorogenic acid, caffeine, quinic acid, and mangiferin, share similarities with the main active ingredients in coffee. They inhibit infection by preventing the binding of the COVID-19 virus spike protein with ACE2.

A study on the impact of dietary habits on COVID-19 infection, published in the journal Nutrients in 2021, analyzed data from 37,988 individuals in the UK Biobank. The study concluded that habitual intake of one or more cups of coffee per day was associated with a 10 percent reduction in the risk of COVID-19 infection, compared to those who drink less than one cup daily.

Coffee Reduces Cardiovascular Disease, Mortality Risk

Mr. Zhang noted that the benefits of coffee are gaining attention and recognition. In recent years, numerous large-scale community studies highlighting the health advantages of coffee have been published.

Another study, published in the European Journal of Preventive Cardiology in 2022, conducted large-scale population research using data from the UK Biobank. This 10- to 15-year follow-up study on 468,629 individuals without clinical manifestations of heart disease revealed that moderate coffee consumption (0.5 to 3 cups per day) was associated with reduced all-cause mortality, cardiovascular mortality, and incident stroke.

The benefits of coffee are not limited to the larger coffee-consuming Western population—they also extend to populations in Asia, where coffee consumption is relatively lower. A prospective cohort study, published in the International Journal of Epidemiology in 2022, involving 529,362 individuals in Asian countries (China, Japan, Korea, and Singapore), found an association between coffee consumption and reduced all-cause mortality, as well as lower risks of mortality from cardiovascular disease and cancer.

Anti-Inflammatory Benefits

Mr. Zhang stated that, apart from its role in preventing cancer and cardiovascular diseases, regular moderate coffee drinking is beneficial for improving metabolism, reducing inflammation, alleviating gout and diabetes risks, and even extending lifespan.

The mechanisms by which coffee improves health conditions are not fully understood, but one reason may be the reduction of inflammatory factors in the body. A 2017 study published in the journal Nature Medicine demonstrated that coffee can lower the levels of the inflammatory cytokine interleukin-1beta, thereby reducing the risk of diseases such as cancer and cardiovascular diseases, and contributing to an extended lifespan.

The study found that the risks of age-related cardiovascular diseases and mortality are closely linked to the inflammatory process, triggered by circulating nucleic acid metabolites or breakdown products in the blood. This pro-inflammatory effect may potentially be counteracted by caffeine and its metabolites.

“More than 90 percent of all noncommunicable diseases of aging are associated with chronic inflammation,” David Furman, lead author of the study and an associate professor at the Stanford Institute for Immunity, Transplantation, and Infection, wrote in a Stanford Medicine article. He further explained that evidence from more than 1,000 papers suggests that chronic inflammation can contribute to various conditions, including cancers, cardiovascular disease, osteoarthritis, Alzheimer’s disease, other forms of dementia, and even depression.

Mr. Zhang noted that coffee’s association with longevity is linked to various bioactive compounds present in coffee, such as chlorogenic acid, caffeic acid, trigonelline, cafestol, and melanoidins formed during the roasting process. All of these substances exhibit antioxidant properties to some extent.

Coffee With Milk for Combating Depression

The global incidence of depression is on the rise, and about one-fifth of U.S. adults have been diagnosed with this condition. Multiple studies have found that moderate coffee consumption may alleviate mental issues such as depression and anxiety, and the addition of milk to coffee shows even better results.

A study published in the journal Psychiatry Research in August 2023 conducted a tracking survey on 146,566 participants using data from the UK Biobank. The research revealed a J-shaped association between coffee intake and incident depression and anxiety, with participants drinking 2 to 3 cups of coffee per day experiencing the lowest risk of developing mental disorders. Additionally, researchers categorized participants based on the type of coffee consumed and observed that the reduction in depression risk was most notable among those who consumed “milk-coffee,” unsweetened coffee, and ground coffee.

A study published in the Journal of Agricultural and Food Chemistry in January 2023 found that adding milk—rich in protein and amino acids—to coffee, which is abundant in polyphenols, enhances the anti-inflammatory effects of coffee by forming potent phenolic-amino acid complexes.

Mr. Zhang pointed out that coffee can help to combat depression through two mechanisms. First, coffee can increase the population of beneficial bacteria in the gut. According to Mr. Zhang, as these bacteria multiply, they contribute to improved sleep quality and reduce worries through the gut-brain axis. Second, the aroma of coffee beans can trigger the release of feel-good hormones in the body, enhancing overall happiness.

Drinking Coffee the Right Way to Enhance Benefits

Mr. Zhang said he typically enjoys three cups of coffee each day—two in the morning and one in the afternoon. Because of a mild gastroesophageal reflux issue, he avoids drinking coffee on an empty stomach as it may worsen the symptoms. Instead, he enjoys his coffee after meals, often with added milk to mitigate its impact on the digestive system.

During busy workdays, Mr. Zhang mainly opts for instant coffee, but when time allows, he enjoys roasting and grinding his own coffee beans. Occasionally, he pairs his coffee with cakes or cookies for a delightful treat.

Mr. Zhang said that in the past, there was a trend of drinking plain black coffee for health reasons. However, the newer research found that coffee with milk added offers greater benefits. That’s because the cysteine in milk combines with polyphenols in coffee to form complexes, enhancing its anti-inflammatory activity.

He does not recommend adding nondairy creamer or sugar to coffee. Nondairy creamer mainly contains trans fatty acids, which are detrimental to the body, while sugar may contribute unnecessary calories.

Coffee enthusiasts who are prone to insomnia should be mindful of the timing of their coffee drinking, Mr. Zhang said. If you are having just one cup per day, the ideal time for coffee is at about 10 a.m. For those enjoying two cups or more daily, the second cup is recommended in the afternoon, at about 3 p.m. or 4 p.m., especially when feeling tired, as coffee during this time can help to enhance alertness. Individuals prone to insomnia should steer clear of coffee in the evening, particularly after 7 p.m. or 8 p.m. For those who are sensitive to caffeine, even the afternoon may be too late.

From the perspective of health benefits, Mr. Zhang said, there is not much difference among various types of coffee, whether in terms of origin or brewing methods—it’s all about personal preference.

However, he emphasized that excessive coffee consumption can lead to side effects such as insomnia and restlessness. Additionally, individuals with osteoporosis, those prone to insomnia, and children younger than age 12 should be cautious and consider limiting or avoiding coffee intake.