Going green reduces COVID risk: Plant-based diets slash risk by up to 41%

By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Jan 11 2024

In a recent study published in the journal BMJ Nutrition, Prevention & Health, researchers investigated the associations between dietary choices and severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection risk. Their evaluation of 424 omnivores and 278 vegetarians revealed that individuals choosing plant-based diets are up to 39% less likely to contract a SARS‑CoV‑2 infection when compared to their meat-eating counterparts. Additionally, plant-based diets were associated with better body mass indices (BMIs) and lower obesity and overweight prevalence, highlighting its benefits. This study, therefore, presents plant-based diets as having a potentially protective effect against COVID-19, revealing a behavioral change that may retard the pandemic's spread.

Study: Vegetarian and plant-based diets associated with lower incidence of COVID-19. Image Credit: Alkema Natalia / Shutterstock

A case for avoiding meat

The coronavirus disease 2019 (COVID-19) pandemic represents one of the worst pandemics in human history, with a death toll surpassing 7 million since its discovery in late 2019. In the United States of America (US) alone, more than 1 million individuals have died of the disease. In comparison, the Spanish influenza of 1918, America's second-worst pandemic, claimed approximately 675,000 lives. The COVID-19-associated infrastructure, medical, and economic breakdown remains unprecedented globally.

The development of COVID-19 vaccines in tandem with government-enforced social distancing policies has significantly hampered or even reversed the spread of SARS-CoV-2, the pathogen behind COVID-19. Unfortunately, the emergence of novel virus subvariants presents a drawback in vaccination efforts, with the possibility of a pandemic resurgence still genuine. Drawing from the success of social distancing restrictions, recent research has explored the merits of modifiable behaviors in combatting COVID-19. Diet is one of these behaviors.

Reports from Okinawa, Japan, and sub-Saharan Africa reveal that these regions, already noteworthy for the longevity of their inhabitants, suffered far fewer SARS-CoV-2 infections and mortality compared to their counterparts from North Africa, North America, and Europe. Despite their substantially differing socioeconomic and geopolitical contexts, a commonality between Okinawa and sub-Saharan Africa is their predominant diet – most citizens of these regions follow a vegetarian lifestyle.

Elucidating dietary choices' impacts and potential benefits in the fight against COVID-19 would help provide consumers and medical practitioners with the information needed to safeguard themselves against the ongoing pandemic.

About the study

In the present study, researchers investigated the associations between diet type (omnivorous or vegetarian) and SARS-CoV-2 infection risk. Their study cohort comprised 702 adult Brazilian volunteers recruited as a part of the Pandora Project, a prospective study on dietary influences on health. Data was collected via online questionnaires and included information on sociodemographics, lifestyle (including smoking), medical history, and eating behaviors (dietary choices and habits).

Based on their eating behaviors, participants were divided into omnivorous (consumption of animal-origin food more than three times per week) and plant-based (including flexitarians, lacto-ovo-vegetarians, strict-vegetarians, and vegans). The Brazilian Institute of Geography and Statistics (IBGE) methodology was used to classify age, education, ethnicity, and religion. Smoking status was evaluated using the Surveillance of Chronic Diseases by Telephone Survey (Vigitel) questionnaire.

Physical activity metrics were collected and analyzed using the International Physical Activity Questionnaire-Short Form (IPAQ), which comprises leisure, domestic, transportation, and work contexts. Self-reported weight and height data was used to calculate all participants' body mass indices (BMIs). In addition to the presence and severity of prior SARS-CoV-2 infections, medical history data was used to analyze vaccination status and chronic diseases (cancers, cardiovascular diseases), all of whom comprised statistical covariates.

Statistical analyses included Fisher's exact test and chi-squared (Χ²) tests to elucidate differences in categorical variables and regression models (logistic and linear) to compare findings between cases (plant-based diets) and controls (omnivores). Demographic and medical data were used to correct these models where relevant.

Study findings

Of the 723 individuals initially recruited into the study, 21 were found to provide incongruent information and were excluded from data analysis. Of the remaining 702, 424 were omnivorous, and 278 followed plant-based diets. Regression analyses found no significant differences between these groups based on age, sex, vaccination status, smoking, or degree of isolation. This confirms the validity of between-group comparisons based on dietary choice as the treatment of interest.

Overall health analyses revealed the omnivores group to depict significantly higher BMI, incidences of overweight and obesity, and total pre-existing medical conditions when compared to the plant-based cohort. Physical activity was higher in the plant-based group than their omnivorous counterparts. Together, these results suggest that individuals subscribing to plant-based dietary regimes are more health-conscious and healthier overall than their meat-eating counterparts.

Crude and multivariable logistic regression analyses revealed that plant-based diets had a 38% lower incidence rate than meat-based diets, with demographic corrections revealing a 39-41% lower infection risk in the former cohort. However, following infection contraction, dietary choices were not found to have a statistically significant effect on disease severity.

Conclusions

The present study reveals the protective effect of meat-based diet abstinence against COVID-19 infections. Comparisons between 424 omnivorous and 278 plant-based diet consumers depicted that the latter is overall the healthier choice, resulting in substantially lower BMI, lower risk of overweight and obesity, and lower chronic disease prevalence. The highlight of this study is that vegetarians are at 39-41% less risk from COVID-19 than their meat-eating counterparts. However, the plant-based diet does not additionally reduce disease severity once the infection is contracted.