As the COVID-19 pandemic intensifies, it has become increasingly clear that peoples’ daily lives will continue to be disrupted for the foreseeable future. Likewise, many public health officials have emphasized that it will be important to evaluate and enact measures to reduce the infection rate, death toll, and overall suffering resulting from the outbreak. Along with encouraging measures such as social distancing, hand washing, and staying home if ill, many have emphasized the need to incorporate other strategies to reduce the long-term impacts of the pandemic.1,2
Unfortunately, some people—especially those who are older or have a preexisting condition—may have dysfunctional immune systems that fail to keep the response to particular pathogens such as COVID-19 in check. 3 The ability for patients to mount more robust immune responses can help fight viruses and may help keep some of them out of hospitals, leaving room for those in most dire need.3 A significant factor in the strength of one’s immune system is their nutrition.3,4 Likewise, nutrition may be a key part of long-term strategies to alleviate public health crises such as COVID-19.5
Although there is currently no evidence regarding specific dietary factors that can protect people from acute infections like COVID-19, eating a healthy diet can aid in optimal immune system functioning as well as give people a sense of control in an uncertain time.3-5 Here, we present 4 diet-focused factors that should be considered on a national level to combat COVID-19.
Immune System Boosting Nutrition
Increased consumption of key nutrients seems to strengthen the immune system, whereas reduced consumption of these nutrients leads to a less responsive immune system and increased susceptibility to infection. 5,6 Such nutrients include vitamins A, C, D, E, B-6, micronutrients such as zinc, selenium, iron, as well proteins and probiotics.5-7
Vitamin A supports antibodies by aiding their response to toxins and foreign substances. Food sources of vitamin A include carrots, spinach, broccoli, squash, kale, sweet potatoes, cantaloupe and mangoes. 6,7 Vitamin C assists in increasing blood levels of antibodies and assists in the differentiation of lymphocytes. Studies have also shown that increased levels of vitamin C may reduce the duration of cold symptoms. 6-8 Vitamin C can be found in food sources such as oranges, strawberries, cabbage, cauliflower, brussels sprouts, and green and red peppers. 6-8 Vitamin D may help mitigate the risk of developing viral infections in the upper respiratory tract.6,9 Food sources of Vitamin D include fatty fish, eggs, fortified milk, cheese, fortified juice and mushrooms. 6,7,9 Zinc assists cells in the immune system to grow and differentiate. According to one study, zinc supplements can decrease the duration of symptoms of the common cold. 5-7,10 Food sources of zinc include lentils, nuts, seeds, beans, chickpeas, oysters, lobster, and meat.6,7 Proteins are also crucial building blocks for immune cells and antibodies. Sources of protein can be animal- or plant-derived and may include fish, milk , eggs, yogurt, as well as beans, lentils, nuts and seeds. 5-7,11 Probiotics and prebiotics may bolster the health of the microbiome, which in turn assists the immune system.5-7 Sources of probiotics include yogurt and other fermented foods. Sources of prebiotics include beans, artichokes, asparagus, garlic, whole grains, onions and bananas.5-7 Importantly, several of these nutrients can support reduction of excess inflammation and tissue damage caused by viral infection. 12
Although there is currently no evidence regarding specific dietary factors that can protect people from acute infections like COVID-19, eating a healthy diet can aid in optimal immune system functioning as well as give people a sense of control in an uncertain time.
Malnourished individuals have increased risk of becoming ill
Previous infectious disease outbreaks have demonstrated that malnourishment (either hunger or obesity) is a risk factor in severe disease. 13 Malnourished individuals have impaired immune systems and are at increased risk for becoming seriously ill, experiencing a longer period of illness, and mortality.13
In the climate of the current COVID-19 emergency, addressing malnourishment is even more vital. Due to some families having inadequate household income to purchase school lunches for children, the School Breakfast Program provides free or reduced-price breakfast to nearly 15 million children while the National School Lunch Program provides free or low-cost lunches to nearly 30 million children. 14,15 For most US children, breakfast and lunch account for approximately half of daily calorie intake. Of note, school meals provide approximately 77% of daily milk and 41% of vegetable intake. 16 As COVID-19 has forced the shutdown of many schools, access to healthy meals is no longer available for members of this population. With the shutdown of at least 124,000 US schools, compounded by the growing loss of wages and increasing rates of unemployment, this critical lifeline of healthy food is gone, and the logistics of feeding many school-aged children has become a challenge. 17
On a national scale, even a small decrease in risk of severe infection can make a significant difference in tempering the impact of COVID-19 on hospitals. Consequently, it is important for communities to try to find alternative strategies to reduce the number of patients with severe infections, and, according to many, addressing malnourishment may do just that.
Increased risk of CVD and diabetes that are attributable to poor diet
Another population who are susceptible to severe forms of COVID-19 are those with diabetes and cardiovascular disease (CVD). 4,9,18,19 With CVD weakening the heart’s ability to handle stress and diabetes weakening the immune system, these conditions can predispose people with COVID-19 to the severe excess inflammation which often contributes to lung failure and death.4,9,18,19 According to the American Heart Association, more than half of the US adult population (121.5 million) have some form of CVD, while nearly half of the US adult population (114.4 million) have prediabetes or diabetes.20-22 This is especially concerning when one considers that while the fatality rate is 1% for healthy individuals, the fatality rate jumps to 7.3% and 10.5% for people with diabetes and cardiovascular disease, respectively.18 Increasing consumption of healthy foods is among the key strategies for lessening the severity of existing diabetes and CVD. Suboptimal intake of specific foods and nutrients was associated with an estimated 45% of all deaths due to CVD and diabetes. 18,19 This includes excess sodium intake, insufficient intake of nuts/seeds, high intake of processed meats, low intake of seafood omega-3 fats, low vegetables and low fruit intake. 5,6,18,19
Dehydration can be a physical stressor
Lastly, it is important for people to stay hydrated, as mild dehydration can pose as a physical stressor. According to the Institute of Medicine, the adequate water intake for men and women is 3.7 liters (125 ounces) and 2.7 (91 ounces) per day, respectively.7,23 This recommended daily amount can also come from water-rich sources such as fruits, vegetables and soups.
Containing the current outbreak of COVID-19 is a daunting task to be sure, and we must face it head on, implementing every strategy we have in our disposal—from scientific endeavors seeking treatments and vaccines to public health measures such as improving nutrition and support for the hungry.
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4. Jawhara S. Could intravenous immunoglobulin collected from recovered coronavirus patients protect against COVID-19 and strengthen the immune system of new patients? Int J Mol Sci. 2020 Mar 25;21(7).
5. Harvard T.H. Chan-School of Public Health. Food safety, nutrition, and wellness during COVID-19. https://www.hsph.harvard.edu/nutritionsource/2020/03/25/food-safety-nutrition-and-wellness-during-covid-19/. March 27, 2020. Accessed March 28, 2020.
6. Wintergerst ES, Maggini S, Hornig DH. Contribution of selected vitamins and trace elements to immune system. Ann Nutr Metab. 2007;51:301–323.
7. Drayer L. How to strengthen your immunity during the coronavirus pandemic. Part 1: Diet. https://www.cnn.com/2020/03/25/health/immunity-diet-food-coronavirus-drayer-wellness/index.html. March 27, 2020. Accessed March 28, 2020.
8. Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013 Jan 31;(1):CD000980.
9. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583
10. Science M, Johnstone J, Roth DE, Guyatt G, Loeb M. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012 Jul 10; 184(10): E551–E561.
11. Daly JM, Reynolds J, Sigal RK, Shou J, Liberman MD. Effect of dietary protein and amino acids on immune function. Crit Care Med. 1990 Feb;18(2 Suppl):S86-93.
12. Khomich OA, Kochetkov SN, Bartosch B, Ivanov AV. Redox biology of respiratory viral infections. Viruses. 2018 Aug; 10(8): 392.
13. Quinn SC, Kumar S. health inequalities and infectious disease epidemics: a challenge for global health security. Biosecur Bioterror. 2014 Sep-Oct;12(5):263-73.
14. United States Department of Agriculture. National School Lunch Program. https://www.ers.usda.gov/topics/food-nutrition-assistance/child-nutrition-programs/national-school-lunch-program/. August 20, 2019. Accessed March 30, 2020.
15. United States Department of Agriculture. National School Lunch Program. https://www.ers.usda.gov/topics/food-nutrition-assistance/child-nutrition-programs/school-breakfast-program/. August 20, 2019. Accessed March 30, 2020.
16. Cullen KW, Chen T. The contribution of the USDA school breakfast and lunch program meals to student daily dietary intake. Prev Med Rep. 2016 Nov 28;5:82-85.
17. Education Week. Map: Coronavirus and School Closures. https://www.edweek.org/ew/section/multimedia/map-coronavirus-and-school-closures.html. March 28, 2020. Accessed March 28, 2020.
18. Zimmer K. Why some COVID-19 cases are worse than others. https://www.the-scientist.com/news-opinion/why-some-covid-19-cases-are-worse-than-others-67160. February 24, 2020. Accessed March 28, 2020.
19. Micha R, Penalvo JL, Cudhea F, Imamura F, Rehm CD, Mozaffarian D. Association between dietary factors and mortality from heart disease, stroke, and type 2 diabetes in the United States. JAMA. 2017;317(9):912-924.
20. 2010 Census Briefs. Age and sex composition: 2010. https://www.census.gov/prod/cen2010/briefs/c2010br-03.pdf. May 2011. Accessed March 28, 2020.
21. American Heart Association. Heart disease and stroke statistics-2019 At-a-glance. https://healthmetrics.heart.org/wp-content/uploads/2019/02/At-A-Glance-Heart-Disease-and-Stroke-Statistics-%E2%80%93-2019.pdf. January 19, 2020. Accessed March 28, 2020.
22. National Center for Chronic Disease Prevention and Health Promotion. CDC works to prevent type 2 diabetes and improve the health of all people with diabetes. https://www.cdc.gov/chronicdisease/resources/publications/factsheets/diabetes-prediabetes.htm. March 28, 2020. Accessed March 28, 2020.
23. The National Academies of Sciences, Engineering, Medicine. Dietary reference intakes water potassium sodium chloride and sulfate. https://www.nationalacademies.org/hmd/Reports/2004/Dietary-Reference-Intakes-Water-Potassium-Sodium-Chloride-and-Sulfate.aspx. February 2004. Accessed March 28, 2020.