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Summary of COVID-19 diet studies

Studies   Meta Analysis   Hide extended summaries

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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.,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,

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,,
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