Until the day comes when we can avoid influenzas and coronaviruses like COVID-19, we need to take measures to avoid contracting them while building strong immune systems that are inhospitable to infection. Nutrition is the cornerstone of a person’s healthy immune system. Although there’s much we don’t know about COVID-19 and who catches it, let’s review what we think we know about how nutrients or deficiencies influence immunity.
Exploring the Data on Nutrition in America
It appears that people are most vulnerable to infection when they’re undernourished with nutrient deficiencies, or they have an underlying chronic inflammatory disorder like diabetes, lung or cardiovascular disease, or obesity.
Undernutrition can happen for many reasons, including poor food choices, the aging gut, and reduced absorption, lack of money to buy good food, disease and lack of appetite, drug interference, mouth sores or inability to chew well, poverty, or living in neighborhoods called food deserts where a grocery store may be over 5 miles away and the person lacks transportation, or low nutrition awareness, just to name a few reasons.
Another obstacle is that some of the most nutritious, powerhouse foods like fruits and vegetables are not popular with many people. The CDC reports that only 10 percent of Americans eat the recommended 1 ½-2 cups of fruits and 3 servings of vegetables per day.1 Men, younger adults, and people living in poverty eat the fewest fruits and vegetables.1 Too many kids list French fries, ketchup, and pizza sauce as their only forms of vegetable intake.
Overnutrition, where people eat quantity and not enough quality food can cause imbalances and inadequate nutrient levels even when calories are abundant, and the person looks well fed.
Now it can be easy to think that most Americans are well nourished, but in fact, a study in the American Journal of Clinical Nutrition found that as many as 50% of hospitalized patients and 45% of long-term care patients had malnutrition.2 In 2017, according to Pentagon data, 71 percent of young Americans between 17 and 24 were ineligible to serve in the U.S. military due to health reasons.3
Observational reports in 2020 during the pandemic show a 38 percent increase of food insecurity due to job loss or disruption.4 This was particularly seen in women, people of color, homes with children, and larger households. Coincidently, many essential workers come from these same demographics.5
This is especially worrisome amid a pandemic because “malnourished people have higher risk of becoming ill with longer duration of illness, and greater risk of death.”5
How the Immune System Responds to a Pathogen
Here’s an abbreviated overview of the immune response in the presence of a pathogen from a nutrition point of view.
First, there’s a significant demand for energy from carbohydrates, amino acids, and fatty acids that are already in the body. Lipid-derived mediators such as prostaglandins and leukotrienes are produced along with protein products like immunoglobulins, chemokines, and cytokines. Proteins are also used as substrates to produce DNA and RNA. Many different vitamins and minerals are used as cofactors and direct regulators of gene expression.
On the other hand, damaging reactive oxygen species are created through all this activity, making antioxidant vitamins like C and E, and antioxidant enzymes extremely important—with the enzymes dependent upon adequate supplies of copper, zinc, iron, manganese, and selenium.
Based on this information, it’s easy to see why having adequate nutrition can improve immune function while deficiencies can compromise immunity.6
- Only 1 in 10 Adults Get Enough Fruits or Vegetables. CDC Newsroom; Nov. 16, 2017. Accessed 11/3/2020.
- Keller HH. Malnutrition in the institutionalized elderly: how and why? J Gen Intern Med. 2002; 17:923-932.
- Malnutrition in America 2020. FocusforHealth.org/malnutrition. Accessed 11/13/2020.
- Wolfson J, Leung C. Food insecurity and COVID-19: Disparities in early effects for US adults. Nutrients. 2020;12: 1-13.
- Mozaffarian D, Glickman D, Maydani SN. How your diet can help flatten the curve. CNN Opinion. March 27, 2020. Accessed 11/3/2020. https://www.cnn.com/2020/03/27/opinions/healthy-diet-immune-system-covid-19-mozaffarian-glickman-nikbin-meydani/index.html
- Calder PC. Nutrition, immunity, and COVID-19. Accessed 11/10/2020. https://nutrition.bmj.com/content/early/2020/05/20/bmjnph-2020-000085