According to the findings published in The BMJ Nutrition, Prevention and Health, which examined data from healthcare workers across six countries including the UK, vegetarians are 73 per cent less likely to be hit by coronavirus while self-declared pescatarians were 59 per cent less likely to become ill than those who eat red and white meat.
Low-carbohydrate, high-protein diets appeared to be linked to an increased chance of contracting moderate to severe illness, though the findings were not statistically significant.
The study consisted of a web-based questionnaire that sought to explore the relationship between the respiratory disease and diet, polling 2,300 who had not had the virus and 568 who had.
Among those who had contracted Covid-19, 138 reported moderate to severe symptoms while 430 said they had suffered only a mild or a very mild form of the illness.
Participants were asked to consider the diet they had in the year before Covid and were given 11 choices: whole foods, plant-based diet; keto diet; vegetarian diet; Mediterranean diet; pescatarian diet; Palaeolithic diet; low fat diet; low carbohydrate diet; high protein diet; other; none of the above.
Among the 568 respondents who reported that they had previously been ill, only 41 said they had followed a plant-based diet while just 46 had become ill after pursuing a plant-based or pescatarian diet.
The authors, led by a team in the US, wrote: “In six countries, plant-based diets or pescatarian diets were associated with lower odds of moderate-to-severe Covid-19.
“These dietary patterns may be considered for protection against severe Covid-19.
“Plant-based diets or pescatarian diets are healthy dietary patterns, which may be considered for protection against severe Covid-19.”
Gunter Kuhnle, professor of nutrition and food science at the University of Reading, said: “Since the beginning of the pandemic, there has been a lot of speculation about the impact of diet on disease risk.
“This study attempts to answer this question, but there are a number of limitations that need to be considered: The study relied entirely on self-reporting, and a lot of data have shown that self-reported dietary intake is unreliable.
“In this study, participants were asked about their diet after they were diagnosed with Covid-19, and this might lead to further misreporting, especially among participants who are interested in a potential link between diet and disease.
“Finally, the study has been conducted in different countries with widely different diets – a plant-based diet in Spain or Italy is likely to be different from a mainly plant-based diet in Germany or the UK.”
Professor Francois Balloux of the UCL Genetics Institute said: “The study reports that doctors eating plant-based or pescatarian diets tend to be at significantly lower risk of developing severe Covid-19 symptoms upon infection.
“The sample size is decent, and the analyses look competently performed. Further validation may be required to confirm a direct, causal link between diet and Covid-19 illness severity.
“Indeed, unaccounted lifestyle variables correlated with diet might influence general health of the subjects of the study, and hence how well they coped with Covid-19 infection.”
A vegan diet contains only plants such as vegetables, grains, nuts and fruits and foods made from plants, according to the Eatwell guide. Vegans do not eat foods that come from animals, including dairy products and eggs.
Additional reporting by agencies