Summary of COVID-19 diet studies

568 patient diet study: 72% fewer moderate/severe cases (p=0.02) and 19% fewer cases (p=0.24).
Retrospective healthcare workers in six countries with exposure to COVID-19 patients, showing lower risk of moderate/severe COVID-19 with plant-based diets.
Jun 2021, BMJ Nutrition, Prevention & Health, https://nutrition.bmj.com/content/4/1/257, https://c19p.org/kim4

2. Reis et al., The Association between Lifestyle Risk Factors and COVID-19 Hospitalization in a Healthcare Institution

546 patient diet study: 75% lower hospitalization (p=0.0003).
Retrospective 546 COVID+ patients in the USA, showing lower risk of hospitalization with higher consumption of vegetables.
Oct 2022, American J. Lifestyle Medicine, http://journals.sagepub.com/doi/10.1177/15598276221135541, https://c19p.org/reis6

3. Jagielski et al., Associations of Nutritional Behavior and Gut Microbiota with the Risk of COVID-19 in Healthy Young Adults in Poland

95 patient diet study: 82% fewer cases (p=0.005).
Retrospective 95 people in Poland, showing significantly lower risk of COVID-19 with higher consumption of fruits, vegetables, and nuts. Diets with higher consumption of fruits, vegetables, and nuts had a significantly lower dietary inflammatory index.
Jan 2022, Nutrients, https://www.mdpi.com/2072-6643/14/2/350, https://c19p.org/jagielski

4. Merino et al., Diet quality and risk and severity of COVID-19: a prospective cohort study

296,285 patient diet study: 41% lower severe cases (p<0.0001) and 18% fewer cases (p<0.0001).
Retrospective 592,571 participants in the UK and USA with 31,815 COVID-19 cases, showing lower risk or COVID-19 cases and severity for higher healthful plant-based diet scores. Notably, the assocation was less evident with higher levels of physical activity.
Jun 2021, Gut, https://gut.bmj.com/content/70/11/2096, https://c19p.org/merino2

5. Pavlidou et al., Association of COVID-19 Infection with Sociodemographic, Anthropometric and Lifestyle Factors: A Cross-Sectional Study in an Older Adults’ Population Aged over 65 Years Old

5,197 patient diet study: 55% fewer cases (p=0.0009).
Retrospective 5,197 Greek adults over 65. After adjustment for confounders, COVID-19 infection was independently associated with poor sleep, low physical activity, low Mediterranean diet adherence, living in urban areas, smoking, obesity, depression, anxiety, stress, and poor health-related quality of life.
Nov 2023, Diseases, https://www.mdpi.com/2079-9721/11/4/165, https://c19p.org/pavlidoudt

6. Naushin et al., Insights from a Pan India Sero-Epidemiological survey (Phenome-India Cohort) for SARS-CoV2

diet study: 40% lower seropositivity (p<0.0001).
Retrospective 10,427 volunteers in India, 1,058 anti-nucleocapsid antibody positive, showing lower risk of seropositivity with a vegetarian diet.
Apr 2021, eLife, https://elifesciences.org/articles/66537, https://c19p.org/naushin

7. Ebrahimzadeh et al., Major dietary patterns in relation to disease severity, symptoms, and inflammatory markers in patients recovered from COVID-19

diet study: 69% lower severe cases (p=0.004), 56% lower hospitalization (p=0.07), and 68% improved recovery (p=0.003).
Retrospective 250 recovered COVID-19 patients, showing lower risk of severe cases and shorter recovery and hospitalization times with a healthy diet. Notably, all individual symptoms show lower incidence with a healthy diet with the exception of fever and chills. Fever and chills help the immune system fight infections (shivering helps to raise the body temperature).
Aug 2022, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2022.929384/full, https://c19p.org/ebrahimzadeh

8. Zhao et al., Associations between the Dietary Inflammatory Index and COVID-19 Outcomes in the UK Biobank Cohort

196,154 patient diet study: 24% lower mortality (p=0.13), 28% lower severe cases (p=0.0003), and 15% fewer cases (p<0.0001).
UK Biobank retrospective 196,154 participants with 11,288 COVID-19 cases, showing lower COVID-19 mortality, severity, and incidence for lower dietary inflammatory scores.
Dec 2022, SSRN Electronic J., https://www.ssrn.com/abstract=4300209, https://c19p.org/zhao6

9. Wang et al., Improving Nutritional Status Was Associated with Decreasing Disease Severity and Shortening of Negative Conversion Time of PCR Test in Non-ICU Patients with COVID-19

148 patient diet study: 45% lower severe cases (p=0.06) and 32% improved viral clearance (p=0.03).
Retrospective 148 hospitalized COVID-19 patients in China, showing lower severity and faster viral clearance with improved nutrition.
Jul 2023, Infection and Drug Resistance, https://www.dovepress.com/improving-nutritional-status-was-associated-with-decreasing-disease-se-peer-reviewed-fulltext-article-IDR, https://c19p.org/wang18

10. Wang et al., Adherence to Healthy Lifestyle Prior to Infection and Risk of Post–COVID-19 Condition

798 patient diet study: 9% lower PASC (p=0.43).
Prospective analysis of 32,249 women from the Nurses’ Health Study II in the USA, showing lower risk of PASC with a healthy lifestyle, and in a dose-dependent manner. Participants with 5 or 6 healthy lifestyle factors had significantly lower COVID-19 hospitalization and PASC. BMI and sleep were independently associated with risk of PASC.
Feb 2023, JAMA Internal Medicine, https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2800885, https://c19p.org/wang10dt

11. Perez-Araluce et al., Components of the Mediterranean Diet and Risk of COVID-19

4,403 patient diet study: 78% lower severe cases (p=0.15), 15% fewer symptomatic cases (p=0.31), and 20% fewer cases (p=0.14).
Retrospective 5,194 participants in Spain with 382 COVID-19 cases, showing lower risk of COVID-19 with high adherence to a Mediterranean diet, with statistical significance only when excluding healthcare professionals.
Jan 2022, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2021.805533/full, https://c19p.org/perezaraluce

12. Aghajani et al., Association between dietary antioxidant quality score and severity of coronavirus infection: a case–control study

295 patient diet study: 88% lower severe cases (p<0.0001).
Case control study of 295 COVID-19 patients in Iran, showing lower risk of severe cases with higher dietary antioxidant quality scores, and with higher intake of vitamin D.
Jul 2023, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2023.1174113/full, https://c19p.org/aghajani2

13. Barania Adabi et al., The association between inflammatory and immune system biomarkers and the dietary inflammatory index in patients with COVID-19

500 patient diet study: 99% lower ICU admission (p<0.0001).
Retrospective 500 COVID-19 patients, showing dietary inflammatory index (DII) and energy-adjusted dietary inflammatory index (E-DII) associated with COVID-19 severity.
Mar 2023, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2023.1075061/full, https://c19p.org/baraniaadabi

14. Zamanian et al., The association of dietary approach to stop hypertension (DASH) diet with hospitalization risk in patients with COVID-19

141 patient diet study: 81% lower hospitalization (p=0.002).
Case control study with 53 inpatients and 88 outpatients in Iran, showing lower risk of hospitalization with increased adherence to the DASH (Dietary Approach to Stop Hypertension) diet. Increased intake of fruits, vegetables and low-fat dairy products, and lower intake of sodium and processed/red meat were significantly associated with reduced risk of hospitalization due to COVID-19.
Mar 2023, Clinical Nutrition Open Science, https://www.sciencedirect.com/science/article/pii/S2667268523000050, https://c19p.org/zamanian

15. Tadbir Vajargah et al., Association of fruits, vegetables, and fiber intake with COVID-19 severity and symptoms in hospitalized patients: A cross-sectional study

166 patient diet study: 67% lower severe cases (p=0.003).
Retrospective 250 hospitalized patients in Iran, showing higher consumption of fruits, vegetables, and fiber associated with lower COVID-19 severity.
Sep 2022, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2022.934568/full, https://c19p.org/tadbirvajargah

16. Zargarzadeh et al., Higher Adherence to the Mediterranean Dietary Pattern Is Inversely Associated With Severity of COVID-19 and Related Symptoms: A Cross-Sectional Study

169 patient diet study: 77% lower severe cases (p=0.0002).
Retrospective 250 COVID-19 patients in Iran, showing lower risk of severe disease with greater adherence to a Mediterranean diet.
Jul 2022, Frontiers in Medicine, https://www.frontiersin.org/articles/10.3389/fmed.2022.911273/full, https://c19p.org/zargarzadeh

17. Firoozi et al., The Association between Energy-Adjusted Dietary Inflammatory Index, Body Composition, and Anthropometric Indices in COVID-19-Infected Patients: A Case-Control Study in Shiraz, Iran

diet study: 65% fewer cases (p<0.0001).
Retrospective 133 COVID-19 patients and 322 controls, showing higher risk of COVID-19 for diets that have a higher inflammatory index (E-DII).
Mar 2022, Int. J. Clinical Practice, https://www.hindawi.com/journals/ijclp/2022/5452488/, https://c19p.org/firoozi

18. Yamamoto et al., Flight attendant occupational nutrition and lifestyle factors associated with COVID-19 incidence

52 patient diet study: 66% fewer cases (p=0.009).
Retrospective 84 flight attendants, 52 reporting COVID-19 status and diet quality, showing higher risk of COVID-19 with lower self-reported diet quality.
Dec 2021, Scientific Reports, https://www.nature.com/articles/s41598-021-04350-0, https://c19p.org/yamamoto

19. Moludi et al., The relationship between Dietary Inflammatory Index and disease severity and inflammatory status: a case–control study of COVID-19 patients

diet study: 92% fewer cases (p<0.0001).
Retrospective 60 COVID-19 hospitalized patients and 60 controls in Iran, showing pro-inflammatory diets associated with COVID-19 cases and severity. IR.KUMS.REC.1399·444, IR.TBZMED.REC.1399·225.
Aug 2021, British J. Nutrition, https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0007114521003214, https://c19p.org/moludi

20. Hou et al., COVID-19 Illness Severity in the Elderly in Relation to Vegetarian and Non-vegetarian Diets: A Single-Center Experience

509 patient diet study: 72% lower severe cases (p=0.23) and 11% fewer moderate/severe cases (p=0.66).
Retrospective 509 COVID-19 patients in Taiwan, showing higher risk of critical COVID-19 cases with non-vegetarian diets.
Apr 2022, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2022.837458/full, https://c19p.org/hou

21. Micek et al., Association of dietary intake of polyphenols, lignans, and phytosterols with immune-stimulating microbiota and COVID-19 risk in a group of Polish men and women

95 patient diet study: 70% fewer cases (p=0.09).
Dietary analysis of 95 adults in Poland, showing lower risk of COVID-19 with higher intake of polyphenols, lignans, and phytosterols. Results were statistically significant for total phytosterols, secoisolariciresinol, β-sitosterol, matairesinol, and stigmasterol. Authors suggest that beneficial effects on gut microbiota and immune function may contribute to the lower risk.
Aug 2023, Frontiers in Nutrition, https://www.frontiersin.org/articles/10.3389/fnut.2023.1241016/full, https://c19p.org/micek

22. Zhou et al., Impact of ultra-processed food intake on the risk of COVID-19: a prospective cohort study

20,507 patient diet study: 16% fewer cases (p<0.0001).
Prospective study of 41,012 UK Biobank participants, showing higher risk of COVID-19 cases with ultra-processed food consumption.
Aug 2022, European J. Nutrition, https://link.springer.com/10.1007/s00394-022-02982-0, https://c19p.org/zhou7

23. Yue et al., Long-term diet and risk of SARS -CoV-2 infection and Coronavirus Disease 2019 (COVID-19) severity

diet study: 19% fewer cases (p=0.008).
Analysis of 42,935 participants showing lower risk of COVID-19 with healthier diets. Risk of severe cases was also lower with healthier diets, while not reaching statistical significance. Severity results are only provided with diet indices as a continuous variable.
Aug 2022, The American J. Clinical Nutrition, https://academic.oup.com/ajcn/advance-article/doi/10.1093/ajcn/nqac219/6659183, https://c19p.org/yue

24. Magaña et al., Influence of mediterranean diet on survival from covid-19 disease

89 patient diet study: 53% lower mortality (p=0.05).
Retrospective 89 COVID-19 patients in Spain, showing lower mortality with adherence to the Mediterranean diet.
Dec 2021, Clinical Nutrition ESPEN, https://www.sciencedirect.com/science/article/pii/S2405457721009293, https://c19p.org/magana

25. Nguyen et al., Single and Combinative Impacts of Healthy Eating Behavior and Physical Activity on COVID-19-like Symptoms among Outpatients: A Multi-Hospital and Health Center Survey

2,136 patient diet study: 15% fewer symptomatic cases (p=0.006).
Analysis of 3,947 participants in Vietnam, showing significantly lower risk of COVID-19-like symptoms with physical activity and with a healthy diet. The combination of being physically active and eating healthy reduced risk further compared to either alone. The analyzed period was Feb 14 to Mar 2, 2020, which may have been before testing was widely available.
Sep 2021, Nutrients, https://www.mdpi.com/2072-6643/13/9/3258, https://c19p.org/nguyen2dt

26. Mohajeri et al., Adherence to the Mediterranean Diet Association with Serum Inflammatory Factors Stress Oxidative and Appetite in COVID-19 Patients

600 patient diet study: 25% lower progression (p<0.0001).
Retrospective 600 COVID-19 patients in Iran with moderate/severe CT scans, showing lower prevalence of dyspnea, fever, taste/smell abnormalities, and cough with high adherence to the Mediterranean diet in unadjusted results.
Jan 2023, Medicina, https://www.mdpi.com/1648-9144/59/2/227, https://c19p.org/mohajeri2

27. Mahto et al., Seroprevalence of IgG against SARS-CoV-2 and its determinants among healthcare workers of a COVID-19 dedicated hospital of India

689 patient diet study: 20% lower IgG positivity (p=0.32).
Retrospective 689 healthcare workers in India, showing non-statistically significant lower risk of IgG positivity with a vegetarian diet in unadjusted results.
Feb 2021, American J. Blood Research, https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC8010601/, https://c19p.org/mahtodt

28. Ahmadi et al., Lifestyle risk factors and infectious disease mortality, including COVID-19, among middle aged and older adults: Evidence from a community-based cohort study in the United Kingdom

468,569 patient diet study: 3% higher mortality (p=0.85).
Retrospective 468,569 adults in the UK, showing no significant difference in COVID-19 mortality based on diet quality, however significantly lower mortality was seen with higher diet quality for pneumonia and infectious diseases.
Aug 2021, Brain, Behavior, and Immunity, https://www.sciencedirect.com/science/article/pii/S088915912100180X, https://c19p.org/ahmadi2dt

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