The link between plant-based eating and COVID-19 immunity

Aim

In this observational study, Vegetarian and plant-based diets associated with lower incidence of COVID-19, the researchers explore whether omnivorous, flexitarian, or plant-based dietary habits had an impact on the rate of COVID-19 infection.

It additionally aimed to identify key food groups within the dietary patterns which may be protective.

It explores the nuances between the dietary patterns considered and the impact of interlinked factors such as body weight on immunity.

Method

702 adult volunteers from Brazil participated in this prospective observational study, recruited online between March and July 2022.

Participants completed questionnaires on sociodemographic variables, lifestyle, medical history and diet, and were then categorised as omnivorous or plant-based based on these self-reported dietary habits.

Follow-up of at least 6 months was requested. The co-variables were integrated or adjusted for in four regression models assessing the association between dietary pattern, food groups consumed and COVID-19 incidence, severity and duration.

Key findings

Of the total sample (n=702), 47.0% reported a diagnosis of COVID-19 during the study period, representing the incidence of infection.

The plant-based group had significantly fewer infections than the omnivorous group (39.9 vs 51.6%, p=0.005). This significant difference prevailed when adjusted for sex, age, ethnicity, smoking status, BMI, physical activity, vaccination and pre-existing medical conditions.

It was also found that when further subdivided into vegetarian and flexitarian diets, the difference in incidence remained for both groups in comparison to the omnivorous diet, even when controlled for the above variables. The protective impact was greatest for the vegetarian condition.

The plant-based group also had a lower rate of moderate-severe infection comparative to the omnivorous group (11.2 vs 17.7%, p=0.005).

The duration of symptoms displayed no difference between the groups observed.

There were key observable differences in the baseline characteristics of the groups:

• Sex, age, vaccination, smoking status and degree of isolation were not significantly different between the two main groups considered.

• The plant-based group did however have a higher rate of post-graduate participants compared to the lower educational level in the omnivorous group, and also did more physical activity.

• The omnivorous group had a higher rate of pre-existing medical conditions and elevated BMI.

Food group considerations

Food groups were also considered independently for which, the plant-based group was divided into vegetarian and flexitarian. Those who reported following vegetarian diets had a higher intake of vegetables, legumes and nuts, and a lower intake of dairy, meats and eggs.

A majority of the benefits were observed in the plant-based group.

Food-group consumption was not significantly different between the omnivore and flexitarian groups.

Therefore, the difference in the plant-based groups COVID-19 incidence and outcomes can be linked to key food groups mentioned above.

Conclusion

Those following a plant-based diet have a lower incidence of COVID-19 even when controlled for differences in baseline variables.

For the greatest protection, it is suggested vegetarian diets and diets which exclude meat are preferred.

Population protective measures should think beyond measures like isolation and vaccination and consider dietary changes for a potentially cost-effective, efficacious reduction in infection incidence.