The chances of developing moderate to severe COVID-19 could be lower among people who eat a plant-based or pescatarian diet, new research has suggested.
A six-country observational study, published in BMJ Nutrition Prevention & Health, found people with those diets had 73% and 59% lower odds, respectively, of severe disease.
Because several studies have suggested that diet might have an important role in symptom severity and illness duration of COVID-19, the researchers drew on the survey responses of 2884 frontline doctors and nurses, working in France, Germany, Italy, Spain, the UK and the US, with extensive exposure to SARS-COv-2.
They were all part of a global network of healthcare professionals registered with the Survey Healthcare Globus network for healthcare market research.
The online survey, which ran between July and September 2020, was designed to find information about respondents’ dietary patterns and the severity of any COVID-19 infections they had had. It also gathered data on personal background, medical history, medication use, and lifestyle.
The various diets were combined into plant-based; pescatarian/plant-based; and low carb-high protein diets.
Out of all the respondents, 568 said they had had symptoms consistent with COVID-19 or had had a positive swab test for the infection. The remaining 2316 said they had neither experienced any symptoms nor had tested positive.
Of the 568 clinicians, 138 reported having had moderate to severe COVID-19 infection, while 430 said they had had very mild to mild COVID-19 infection.
The researchers found that respondents who reported plant-based or plant-based/pescatarian diets had, respectively, 73% and 59% lower odds of moderate to severe COVID-19 infection, compared with other diets.
Those who said they ate a low carb-high protein diet were found to have nearly four times the odds of moderate to severe COVID-19 infection compared to those on plant-based diets.
The researchers said these associations remained when weight/BMI and co-existing medical conditions were factored in, but they found no association between any type of diet and the risk of contracting COVID-19 infection or length of illness.
The authors say this is an observational study that relied on individual recall rather than on objective assessments, and the definition of certain dietary patterns may vary by country. Men also outnumbered women in the study.
Nevertheless, they add plant-based diets are rich in nutrients, especially phytochemicals, vitamins and minerals, all of which are important for a healthy immune system, while fish is an important source of vitamin D and omega-3 fatty acids.
Shane McAuliffe, deputy chair of the NNEdPro Nutrition and COVID-19 Taskforce, said: “The trends in this study are limited by study size (small numbers with a confirmed positive test) and design (self-reporting on diet and symptoms) so caution is needed in the interpretation of the findings.
“However, a high quality diet is important for mounting an adequate immune response, which in turn can influence susceptibility to infection and its severity.
“This study highlights the need for better designed prospective studies on the association between diet, nutritional status and COVID-19 outcomes.”
Kim H, Rebholz CM, Hegde S et al. Plant-based diets, pescatarian diets and COVID-19 severity: a population-based case–control study in six countries. BMJ Nutrition Prevention & Health 8 June 2021; doi 10.1136/bmjnph-2021-000272
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