Vegetarians and pescatarians are up to 73% less likely to develop severe Covid-19 than meat-eaters, a Johns Hopkins study finds. But no association was observed between any type of diet and the risk of contracting Covid-19 infection or length of the subsequent illness.
Plant-based vegetarian diets reduce the risk of moderate to severe Covid-19 by up to 73% and a fish-based pescatarian diet reduces the risk by 59%. Previous studies had shown a link between diet and the severity and duration of a Covid-19 infection, which the team wanted to examine in more detail.
Drawing on a survey of 2,884 frontline doctors and nurses exposed to the virus between July and September 2020, the team from Johns Hopkins Bloomberg School of Public Health looked into diet and Covid-19 severity.
As it was a self-reported observational study they couldn't say why this was the case, but suspected it may be due to increased vitamins, nutrients and minerals in a plant-based diet that are vital for a healthy immune system. The research, led by Dr Yoko Yokoyama, from Keio University in Fujisawa, found vegetarians had 29.2 milligrams less of total cholesterol per decilitre (one tenth of a litre) than meat-eaters.
Volunteers involved in the survey faced extensive exposure to SARS-CO-v2, the virus responsible for Covid-19 infection throughout the pandemic. They were working in France, Germany, Italy, Spain, the UK and the US last summer and were all part of the Survey Healthcare Globus market research network.
The researchers used this network to identify medical professionals, including doctors and nurses, at high risk of COVID-19 infection as a result of their jobs. The survey also gathered information on personal background, medical history, medication use, and lifestyle.
They explored three diets: plant-based that was higher in vegetables than meat, pescatarian that was high in vegetable and fish, and a low carb-high protein diet.
Of the volunteers involved in the survey, 568 said they had Covid-19 symptoms or no symptoms but had positive swab test for the infection, and another 2,316 said they hadn't had any symptoms or tested positive.
Among the 568 cases, 138 clinicians said they had a moderate to severe Covid-19 infection and the remaining 430 said they had a very mild to mild infection.
The team then factored in several influential variables, including age, ethnicity, medical specialty, and lifestyle factors, such as smoking and physical activity levels.
They found that those taking part in the survey who eat a plant or fish-based diet had significantly lower odds than meat eaters of developing a severe strain of Covid. In comparison, those who eat a low carb-high protein diet had four times the odds of developing a moderate to severe infection than plant-eaters.
These associations held true when weight (BMI) and co-existing medical conditions were also factored in.
There were a number of issues with the study, the team explained, including the fact men outnumbered women, so the findings may not be applicable to women. This was also an observational study, and so can't establish cause, only correlation. It also relied on individual recall rather than on objective assessments, and the definition of certain dietary patterns may vary by country, point out the researchers.
Study details
Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries
Published in June 2021, BMJ Nutrition Prevention & Health
Authors: Hyunju Kim, Casey M Rebholz, Sheila Hegde, Christine LaFiura, Madhunika Raghavan, John F Lloyd, Susan Cheng, and Sara B Seidelmann.
Abstract
Background
Several studies have hypothesised that dietary habits may play an important role in COVID-19 infection, severity of symptoms, and duration of illness. However, no previous studies have investigated the association between dietary patterns and COVID-19.
Methods
Healthcare workers (HCWs) from six countries (France, Germany, Italy, Spain, UK, USA) with substantial exposure to COVID-19 patients completed a web-based survey from 17 July to 25 September 2020. Participants provided information on demographic characteristics, dietary information, and COVID-19 outcomes. We used multivariable logistic regression models to evaluate the association between self-reported diets and COVID-19 infection, severity, and duration.
Results
There were 568 COVID-19 cases and 2316 controls. Among the 568 cases, 138 individuals had moderate-to-severe COVID-19 severity whereas 430 individuals had very mild to mild COVID-19 severity. After adjusting for important confounders, participants who reported following ‘plant-based diets’ and ‘plant-based diets or pescatarian diets’ had 73% (OR 0.27, 95% CI 0.10 to 0.81) and 59% (OR 0.41, 95% CI 0.17 to 0.99) lower odds of moderate-to-severe COVID-19 severity, respectively, compared with participants who did not follow these diets. Compared with participants who reported following ‘plant-based diets’, those who reported following ‘low carbohydrate, high protein diets’ had greater odds of moderate-to-severe COVID-19 (OR 3.86, 95% CI 1.13 to 13.24). No association was observed between self-reported diets and COVID-19 infection or duration.
Conclusion
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.
Full study in BMJ Nutrition Prevention & Health (Open access)
See also from the MedicalBrief archives:
Supplements reduce COVID risk in women but not men — Large observational study
High vitamin D levels may protect against COVID-19, especially for Black people