Optimal nutrition is one of the most important determinants of health. Adequate nutrition before and after an infection is therefore very important. With regard to the prevention and development of COVID-19, only a few studies on dietary patterns have been carried out to date. Brazilian researchers from the University of São Paulo have now taken on this task.
COVID-19 was not the world’s first pandemic. However, in order to prevent the spread of this highly contagious disease, it quickly led to global changes like no other before it. The USA and Brazil recorded the highest number of cases and deaths. In contrast to western regions, the Japanese island of Okinawa had a low COVID-related mortality rate. Mortality and infection rates were also lower in sub-Saharan Africa than in North Africa, Europe and North America. These populations in Japan and sub-Saharan Africa have different geopolitical and socioeconomic contexts, but similar dietary habits: Both eat a predominantly plant-based diet, eat less meat and have a low prevalence of chronic diseases (such as metabolic syndrome), which has likely contributed to the lower COVID-19 mortality.
Dr. Julio Cesar Acosta-Navarro, Clinical Emergency Unit, Heart Institute, Hospital da Clinicas HCFMUSP, University of São Paulo, and colleagues conducted an observational study in which 702 participants provided information on sociodemographic characteristics, dietary habits and COVID-19 levels by questionnaire between March and July 2022. In addition, their lifestyle was determined and their medical history, including COVID-19 vaccination, was checked. Finally, they were divided into two groups based on their eating habits: Omnivores, i.e. “omnivores” with no restrictions (n=424), and “plant eaters”, whose diet is primarily plant-based (n=278). The latter were further divided into those who had meat in their diet three times a week or less (flexitarians, n=87), and vegetarians and vegans (n=191) who did not eat any animal foods such as eggs, milk and dairy products, fish and red meat.
Participants with a plant-based diet fell ill significantly less often
The researchers found no significant differences between the groups in the variables of gender, age, vaccination and degree of isolation. A total of 330 people (47.0%) had a COVID-19 infection. Of these, 224 (31.9%) were diagnosed with mild symptoms and 106 (15.1%) with moderate to severe symptoms. The prevalence of COVID-19 was significantly higher in the omnivorous group than in the plant-based diet group (51.6% vs. 39.9%; p=0.005) (Fig. 1A+B). In terms of the severity of COVID-19 infection, the omnivore group had a higher rate of moderate infections than the plant-based diet group (17.7% vs. 11.2%; p=0.005) (Fig. 1C+D). The duration of symptoms in people with COVID-19 did not differ between the two groups (p=0.549).
Vegetarians consumed more cereals, fruit, vegetables, nuts and seeds as well as vegetable oils and fewer dairy products and eggs (all p<0.001). Conversely, the omnivorous group had a higher meat consumption (p<0.001) than the two plant-based diet groups. The researchers found that the lower prevalence of COVID-19 in the plant-based group compared to the omnivorous group was mainly due to the vegetarian arm. People who ate a plant-based and vegetarian diet were 39% less likely to be infected than those who ate meat. On the other hand, the frequency of consumption of food groups in the omnivorous group was the same as in the flexitarian group. Flexitarians are closer to the omnivorous group in terms of food consumption and lack of protection than vegetarians. Therefore, the positive results in the vegetarian group can be linked to differences in the consumption of food groups: a higher consumption of cereals, fruits, vegetables, nuts and seeds, vegetable oils and a lower consumption of dairy products, eggs and meat, the authors explain.
A plant-based diet is rich in antioxidants, phytosterols and polyphenols, which have a positive effect on various cell types involved in immune function and have direct antiviral properties. In addition, a lower number of leukocytes and neutrophil granulocytes was found in vegetarians. It was also shown that the NK cell activity of peripheral blood lymphocytes is higher in plant-based populations than in omnivorous populations. Participants who consumed meat and plant-based products, were less physically active on a daily basis and were more likely to be overweight and obese were clearly more susceptible to COVID-19 infection and its more severe symptoms and complications.
A diet based on vegetables, nuts and legumes and low in dairy products and meat can help prevent SARS-CoV-2 infection, Dr. Acosta-Navarro and his colleagues conclude. However, they caution that this was a retrospective study and that they had to rely on the information provided by the participants, which was naturally subjective. Nevertheless, in view of these results, they recommend a plant-based or vegetarian diet.
Literature:
- Acosta-Navarro JC, et al: Vegetarian and plant-based diets associated with lower incidence of COVID-19. BMJ Nutrition, Prevention & Health 2024: e000629; doi: 10.1136/bmjnph-2023-000629.
InFo PNEUMOLOGY & ALLERGOLOGY 2024; 6(2): 28-29
