Does a healthy diet reduce the risk of severe Covid-19?

I haven’t written about Covid for a while. Frankly, I was hoping to move on to other health topics by now – we’ve been living under this shadow for almost two years. But Covid-19 is still a central health matter, and many of its mysteries remain unsolved.

One of the most puzzling issues is the incredible variability in disease severity, age notwithstanding. Underlying medical conditions, such as hypertension and diabetes predict a higher likelihood of severe disease, as does obesity, but there’s a lot that can’t be explained by that.

Could nutrition inform some of this disparity? Poor diet is linked with the severity of other infectious diseases. Sound nutritional status supports immunity, lowers the chance of severe, out-of-control inflammation, and malnutrition causes immune deficiency.

This question remains relevant for this pandemic. Although vaccination is the most effective way to prevent severe disease and hospitalization, breakthrough infections are possible and ameliorating those is vital – we’re not completely done protecting ourselves, even with two shots. 

This question is also crucial for other infectious diseases known and yet to come.

Diet and the pandemic

A new study in the journal Gut looks at data from almost 600,000 people in the UK and the US, who were followed from March to December of 2020 by the smartphone based Covid-19 Symptom Study. All participants’ diet was assessed before the study began.

During follow-up almost 32,000 people had Covid-19 infections.

Healthy plant-based diets were associated with lower risk of contracting the disease and of severe Covid-19.

Poor diet quality was associated with lower socioeconomic status, as you might imagine. Healthy behaviors tend to cluster and people who eat healthy may sign on to other health-promoting measures. 

But the association remained strong even after accounting for other healthy behaviors, social determinants of health like education disparities, income inequality, housing insecurity, healthcare access, social isolation, food insecurity, unemployment, public safety etc., and the steps taken to prevent virus transmission such as mask wearing as well as the rates of transmission of Covid-19 in the community.  The authors conclude that: “The joint association of diet quality with socioeconomic deprivation was greater than the addition of the risks associated with each individual factor, suggesting that diet quality may play a direct influence in COVID-19 susceptibility and progression. Our findings suggest that public health interventions to improve nutrition and poor metabolic health and address social determinants of health may be important for reducing the burden of the pandemic.”

Another study of about 3000 health workers from France, Germany, Italy, Spain, UK, and the US showed that those on a plant based or pescatarian diet had lower odds of moderate to severe disease after taking into account other health characteristics, with the vegetarians among the group showing a 73 percent lower chance of moderate to severe illness, and the pescatarians with 59 percent lower odds of significant manifestations.

Again, removing every confounder is impossible, but we already have so many reasons to invest in healthy diets – personally with our own decisions and with public health interventions that increase access and education about the importance of eating well. This isn’t just the Covid-19 pandemic: Poor diets are a risk factor for a long list of chronic diseases, from heart disease to diabetes to cancer.

Dr. Ayala