A study published (June 7th) in the journal BMJ Nutrition reported that ‘plant-based’ diets had a lower risk of developing moderate-to-severe COVID-19 (1). This study involved 2884 front-line healthcare workers from six countries (France, Germany, Italy, Spain, UK, USA) and was a survey based study, relying on self-reporting. 254 reported to have plant-based diets and of those 41 participants had Covid-19 (the others were controls). Of those 41, 37 (90.2%) reported having very-mild-to-mild disease and only 4 (9.8%) had moderate-severe disease. In the total sample, 568 participants had Covid-19. Of these, 430 (75.7%) had very-mild-to-mild disease and 138 (24.3%) had moderate-severe disease. You can see the plant-based group had a much lower percentage (9.8% vs 24.3%) of moderate-severe disease. Does this mean that we should consider a plant-based diet to protect from Covid-19?
The reduction in risk of severe cases appears to be quite dramatic. There is a clear, statistically significant, difference between the risks of moderate-severe disease in the plant-based group versus total groups. When controlling for other factors (i.e. weight, smoking status, etc) this statistically significant difference is conserved . This is crucial because many of these other factors may play a role in response to Covid-19 infection and some (such as weight) have already received a lot of attention on the news for associations with poor outcomes following Covid-19 infection.
There are some limitations to this study. The participants are front-line healthcare workers and primarily male. A large study looking at the general population would be massively beneficial. Additionally, no cases were of patients who had been in critical condition or who died from Covid-19. This was unavoidable in this study. However, further studies could investigate these more severe cases.
The self-reported diets are a major issue for me. The participants were asked follow-up questions about intake of particular foods, such as nuts or milk. This highlights an issue with terminology. Plant-based to me (in the UK) normally means vegan. No meat, fish, dairy or eggs. However, looking at answers to the follow up questions all of these food groups were consumed by the plant-based group (some even at the same rates as the non-plant-based group). For example, the plant-based group consumed significantly less (but not zero) red meat or poultry a week. However, the plant-based group did not consume significantly less fish, milk or eggs. The study even including ‘whole food’ diets as part of the plant-based group. For me this is a massive oversight. I believe a larger study (with more Covid-19 cases) and a better classification of diet patterns is required. Perhaps comparing vegans, vegetarians and omnivores.
The authors cannot say for sure whether the diet is the causal factor and, beyond that, what aspect of the diet may be protective against severe disease. For example, it could be that the important dietary change would be limiting red meat or it could be eating more nuts. This remains unclear from the current study alone. Additional studies are required to better understand the effect of diet on Covid-19 response. With that being said, switching to a plant-based diet is associated with an array of health benefits that are backed by solid science (2). I would encourage anyone to cut down on meat (especially red meat) and dairy for your health and for the environment. However, it remains to be seen whether going vegan will save you from severe Covid-19 infection.
1. 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 2021;bmjnph-2021-000272. doi: 10.1136/bmjnph-2021-000272
2. Medawar, E., Huhn, S., Villringer, A. et al. The effects of plant-based diets on the body and the brain: a systematic review. Transl Psychiatry 9, 226 (2019). https://doi.org/10.1038/s41398-019-0552-0