2023 Namey/Burnett Preventive Medicine Writing Award third-place winner Violeta Foss, OMS-III. reviews and advocates for plant-based nutrition in the fight against COVID-19.
Violeta Foss, OMS-III
2023 Namey/Burnett Preventive Medicine Writing Award Winner, Third Place
Sponsored by the ACOFP Foundation, with winners selected by the ACOFP Health & Wellness Committee, the Namey/Burnett Preventive Medicine Writing Award honors the memory of Joseph J. Namey, DO, FACOFP, and John H. Burnett, DO, FACOFP—dedicated advocates for osteopathic medicine—and recognizes the best preventive medicine blog posts submitted by osteopathic family medicine students and residents.
“An apple a day keeps the doctor away.” The nineteenth-century English-language proverb remains popular to this day, suggesting that a healthy diet can save us frequent visits to the doctor.1 Does this saying hold more truth than we thought?
According to the American Heart Association, the term “Mediterranean diet” encompasses eating habits that emphasize a plethora of fruits, vegetables, grains, nuts, and seeds, with low to moderate amounts of dairy products, eggs, fish, and poultry.2 Populations following the Mediterranean diet largely use minimally-processed plant-based based foods as a source of nutrition. The American Heart Association recommends the Mediterranean diet as a way to reduce the risk for common conditions that may lead to disability, including heart disease, stroke, diabetes, high blood pressure, and high cholesterol.2 A plant-based diet that excludes all animal products may offer even more health benefits such as potentially reversing heart disease.3 In recent years, plant-based or plant-exclusive diets have been gaining recognition as powerful tools against disease, including COVID-19.
The COVID-19 pandemic has highlighted the need for primary, secondary, and tertiary prevention of chronic disease prior to or after a viral infection. Chronic conditions are a leading cause of death and disability in the United States and are responsible for $4.1 trillion in healthcare costs each year.4 When COVID-19 emerged, populations living with chronic disease were among the most vulnerable, prone to severe illness and even death, contributing to the enormous strain placed on American healthcare.5,6
Three years since the first reported COVID-19 cases, antiviral treatment options and vaccines remain effective against severe illness and death.7,8 Yet, the novel disease has led to a multitude of disabling long-term symptoms for many individuals.9 According to the National Center for Health Statistics, 14.6% of all adults in the United States have experienced persistent COVID-19 symptoms, lasting weeks to months after initial recovery and reducing their ability to carry out activities of daily living.9,10
Recognizing new prevention strategies will be crucial in the ongoing battle against COVID-19, its multiple variants, post-COVID conditions, growing list of symptoms, and overall burden of disease. This review aims to present the available literature on the relationship between plant-based diets and COVID-19. While studies on the association between diet and COVID-19 incidence and severity are limited, the literature suggests a possible protective effect of plant-based nutrition.
PubMed was used as a search engine to identify current literature on diet and COVID-19 with the following keywords: “SARS-CoV-2,” “COVID-19,” “plant-based diet,” “Mediterranean diet,” and “vegetarian.” Inclusion criteria included all articles published between 2020 and 2022 that had the abstract, full text, or both available in English. Exclusion criteria included review articles, as well as studies that did not explore the relationship between diet and COVID-19, which was determined by evaluating each individual article for relevance with respect to this review.
The initial keyword search retrieved 35 articles. After inclusion and exclusion criteria were applied, only 6 articles were deemed relevant to the topic of plant-based nutrition and its impact on COVID-19 burden of disease. The notable results from each study are summarized in Table 1: Studies Evaluating the Relationship between Dietary Habits and COVID-19.11-16 Overall limitations include sample size, study duration, possible geographic bias, and survey reporting bias.
Discussion – Pathophysiology of COVID-19
COVID-19 is still a novel disease and much remains to be discovered about the precise way the virus infects cells, causing varying degrees of illness across populations. Studies suggest that the course of the disease is closely tied to an individual’s inflammatory response.17 Dysregulated levels of proinflammatory mediators, including cytokines and chemokines, cause a cascade of changes to the homeostatic state, leading to disease progression and worsening illness severity.18,19 When the aberrant immune response persists after initial recovery, individuals experience post-COVID symptoms, also known as long COVID.20
Plant-Based Nutrition and Its Anti-Inflammatory Properties
While plant-based nutrition is a developing field, the interest in such dietary patterns has been growing. Proteins, antioxidants, and sterols contained in whole-food plant-based sources have demonstrated anti-inflammatory effects.21 Various studies suggest that individuals following low-fat, vegetarian diets have a decreased risk for heart disease and diabetes, as well as chronic disease reversal.3,21 Plant-source nutrients are thought to exert their beneficial effect on these non-communicable diseases, which share a pathophysiology rooted in chronic inflammation.21
The areas of the world known for the particularly extended longevity of their populations, known as “Blue Zones,” follow a predominantly plant-based diet, with no processed food or red meat consumption.22 Interestingly, the Blue Zones do not only see low prevalence of chronic disease, but have also shown minimal COVID-19 mortality, implying a possible association between diet and severe illness prevention.22 Considering the suggested role of inflammation in the pathophysiology of COVID-19, plant-based nutrition may be used as a tool to aid the body’s immune response and mitigate the effects of COVID-19.
Summary of Current Research on the Effects of Plant-Based Diet on COVID-19
Overall, current literature agrees that plant-based nutrition may be an effective way to approach the prevention of COVID-19 and its sequelae. The evaluated studies concur that an association exists between diet and illness severity. Further research is needed to determine if plant-based diets impact the incidence and course of COVID-19 directly or indirectly, by alleviating the underlying conditions that predispose individuals to severe illness. The results and information about the individual studies are summarized in Table 1.
Several studies found evidence that adhering to a plant-based diet was associated with a lower risk of severe COVID-19 illness.11,12,13,16 The data suggest that acquiring daily nutrition from predominantly plant sources may be linked to lower incidence of COVID-19, likely due to a strengthened immune system.11,14,15 When compared to a pescatarian diet, exclusively plant-based diets showed lower odds of experiencing moderate to severe COVID-19.12 Existing research, though still limited, points to the beneficial effects of a plant-based diet, especially as we learn more about the processes underlying disease severity.
COVID-19 has changed the healthcare landscape and emphasized the increasing need for disease prevention. As lifestyle medicine gains popularity as a tool to achieve health, osteopathic family physicians can use existing research to help patients better understand and adopt dietary changes. Nutrition can be used as another safe preventative strategy to mitigate the impact of COVID-19 in the wake of the pandemic. Whole-food plant-based diets may be an important adjunct to pharmacologic therapies and vaccines, conferring unique protection and enhancing the body’s self-healing mechanisms. In the constant quest for preventing disease and improving health, nutrition can provide osteopathic family physicians with another avenue to advocate for their patients and help relieve the vast burden of COVID-19.
- Davis MA, Bynum JP, Sirovich BE. Association between apple consumption and physician visits: appealing the conventional wisdom that an apple a day keeps the doctor away. JAMA Intern Med. 2015;175(5):777-783. doi:10.1001/jamainternmed.2014.5466 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420713/
- What is the Mediterranean Diet? American Heart Association. Updated January 9, 2020. Accessed December 27, 2022. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/mediterranean-diet
- Esselstyn CB. A plant-based diet and coronary artery disease: a mandate for effective therapy. J Geriatr Cardiol. 2017;14(5):317-320. doi:10.11909/j.issn.1671-5411.2017.05.004 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466936/
- National Center for Chronic Disease Prevention and Health Promotion. Centers for Disease Control and Prevention. Updated July 21, 2022. Accessed December 27, 2022. https://www.cdc.gov/chronicdisease/about/index.htm
- COVID-19: People with Certain Medical Conditions. Centers for Disease Control and Prevention. Updated December 6, 2022. Accessed December 27, 2022. https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-with-medical-conditions.html
- Boserup B, McKenney M, Elkbuli A. The financial strain placed on America’s hospitals in the wake of the COVID-19 pandemic. Am J Emerg Med. 2021;45:530-531. doi:10.1016/j.ajem.2020.07.007 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7347328/
- Akinosoglou K, Schinas G, Gogos C. Oral Antiviral Treatment for COVID-19: A Comprehensive Review on Nirmatrelvir/Ritonavir. Viruses. 2022;14(11):2540. doi:10.3390/v14112540 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9696049/
- Barouch DH. Covid-19 Vaccines – Immunity, Variants, Boosters. N Engl J Med. 2022;387(11):1011-1020. doi:10.1056/NEJMra2206573 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9454645/
- Long COVID of Post-COVID Conditions. Centers for Disease Control and Prevention. Updated December 16, 2022. Accessed December 27, 2022. https://www.cdc.gov/coronavirus/2019-ncov/long-term-effects/
- Long COVID – Household Pulse Survey. Centers for Disease Control and Prevention. Updated November 14, 2022. Accessed December 27, 2022. https://www.cdc.gov/nchs/covid19/pulse/long-covid.htm
- Merino J, Joshi AD, Nguyen LH, et al. Diet quality and risk and severity of COVID-19: a prospective cohort study. Gut. 2021;70(11):2096-2104. doi:10.1136/gutjnl-2021-325353 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8500931/
- Kim H, Rebholz CM, Hegde S, et al. Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case-control study in six countries. BMJ Nutr Prev Health. 2021;4(1):257-266. doi:10.1136/bmjnph-2021-000272 https://nutrition.bmj.com/content/4/1/257
- Hou YC, Su WL, Chao YC. COVID-19 Illness Severity in the Elderly in Relation to Vegetarian and Non-vegetarian Diets: A Single-Center Experience. Front Nutr. 2022;9:837458. doi:10.3389/fnut.2022.837458 https://www.frontiersin.org/articles/10.3389/fnut.2022.837458/full
- El Khoury CN, Julien SG. Inverse Association Between the Mediterranean Diet and COVID-19 Risk in Lebanon: A Case-Control Study. Front Nutr. 2021;8:707359. doi:10.3389/fnut.2021.707359 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8363114/
- Jagielski P, Wnęk D, Łuszczki E, et al. Proposition of a New POLA Index to Assess the Immunomodulatory Properties of the Diet and Its Relationship with the Gut Microbiota, Using the Example of the Incidence of COVID-19 in a Group of People without Comorbidities. Nutrients. 2022;14(20):4227. doi:10.3390/nu14204227 https://www.mdpi.com/2072-6643/14/20/4227
- McDaid KM, Chopra M. A Pilot Study to Examine If Dietary Habits Can Affect Symptomology in Mild Pre-Vaccination COVID-19 Cases. Biology (Basel). 2022;11(9):1274. doi:10.3390/biology11091274 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9495586
- Lamers MM, Haagmans BL. SARS-CoV-2 pathogenesis. Nat Rev Microbiol. 2022;20(5):270-284. doi:10.1038/s41579-022-00713-0 https://www.nature.com/articles/s41579-022-00713-0
- Wong LR, Perlman S. Immune dysregulation and immunopathology induced by SARS-CoV-2 and related coronaviruses – are we our own worst enemy? Nat Rev Immunol. 2022;22(1):47-56. doi:10.1038/s41577-021-00656-2 https://www.nature.com/articles/s41577-021-00656-2
- Soltani-Zangbar MS, Parhizkar F, Abdollahi M, et al. Immune system-related soluble mediators and COVID-19: basic mechanisms and clinical perspectives. Cell Commun Signal. 2022;20(1):131. doi:10.1186/s12964-022-00948-7 https://biosignaling.biomedcentral.com/articles/10.1186/s12964-022-00948-7
- Ganesh R, Grach SL, Ghosh AK, et al. The Female-Predominant Persistent Immune Dysregulation of the Post-COVID Syndrome. Mayo Clin Proc. 2022;97(3):454-464. doi:10.1016/j.mayocp.2021.11.033 https://www.mayoclinicproceedings.org/article/S0025-6196(21)00888-0/fulltext
- Kahleova H, Levin S, Barnard N. Cardio-Metabolic Benefits of Plant-Based Diets. Nutrients. 2017;9(8):848. doi:10.3390/nu9080848 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579641/
- Kahleova H, Barnard ND. Can a plant-based diet help mitigate Covid-19? Eur J Clin Nutr. 2022;76(7):911-912. doi:10.1038/s41430-022-01082-https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8777176/