While several studies have indicated that healthy dietary patterns may play a role in improving the immune response, this was the first study to examine the association between dietary patterns and severity of COVID-19 illness.
A 2020 study examining 2884 front-line healthcare workers from France, Germany, Italy, Spain, UK and USA reported that those on plant-based diets or pescatarian diets that were higher in vegetables, legumes and nuts, and lower in poultry and red and processed meats, had 73% and 59% lower odds of moderate-to-severe COVID-19 respectively. It was concluded that plant-based diets or pescatarian diets are healthy dietary patterns which may be considered for protection against severe COVID-19.
Plant-based diets are rich in nutrients, such as phytochemicals (polyphenols and carotenoids), vitamin A, C and E, folate, and minerals (iron, potassium, magnesium). The authors of the paper report that studies show that supplementation of some of these nutrients, specifically, vitamin A, C, D and E, decreased the risk of respiratory infections, such as common cold and pneumonia, and shortened the duration of these illnesses. It is reported that these nutrients support the immune system as they play important roles in the production of antibodies, proliferation of lymphocytes, and reduction of oxidative stress.
The authors also explain fish intake is an important source of vitamin D and omega-3 fatty acids – eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Higher intake of EPA and DHA have anti-inflammatory effects, suppressing the production of pro-inflammatory cytokines (interleukin 1β, tumour necrosis factor α), reducing inflammatory eicosanoid synthesis and oxidative stress. However, they explain that while their results suggest that there is evidence that fish intake may have favourable impacts on respiratory illness, future studies are needed to confirm whether pescatarian diets are associated with patient outcomes in the context of COVID-19.
The report concludes by stating future studies with detailed macro- and micronutrient data are warranted to study associated between dietary intake and COVID-19 severity.
Kim H et al. Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case-control study in six countries. BMJ Nutrition, Prevention & Health. 2021;0. doi:10.1136/bmjnph-2021-000272.