A plant-based diet was associated with lower risk and severity of COVID-19, particularly evident among individuals living in areas with higher socioeconomic deprivation, found a Harvard and Massachusetts General Hospital (MGH) study.
Although metabolic conditions such as obesity and type 2 diabetes have been linked to an increased risk of COVID-19, as well as an increased risk of experiencing serious symptoms once infected, the impact of diet on these risks is unknown.
In a study, published in Gut Journal, people whose diets were based on healthy plant-based foods had lower risks on both counts. The beneficial effects of diet on COVID-19 risk seemed especially relevant in individuals living in areas of high socioeconomic deprivation.
“Previous reports suggest that poor nutrition is a common feature among groups disproportionately affected by the pandemic, but data on the association between diet and COVID-19 risk and severity are lacking,” says lead author Jordi Merino, PhD, a research associate at the Diabetes Unit and Center for Genomic Medicine at MGH and an instructor in medicine at Harvard Medical School.
For the study, Merino and his colleagues examined data on 592,571 participants of the smartphone-based COVID-19 Symptom Study. Participants lived in the UK and the US, and they were recruited from 24 March 2020 and followed until 2 December 2020. At the start of the study, participants completed a questionnaire that asked about their dietary habits before the pandemic. Diet quality was assessed using a healthful Plant-Based Diet Score that emphasises healthy plant foods such as fruits and vegetables.
During follow-up, 31,831 participants developed COVID-19. Compared with individuals in the lowest quartile of the diet score, those in the highest quartile had a 9% lower risk of developing COVID-19 and a 41% lower risk of developing severe COVID-19. "These findings were consistent across a range of sensitivity analysis accounting for other healthy behaviours, social determinants of health and community virus transmission rates," says Merino.
“Although we cannot emphasise enough the importance of getting vaccinated and wearing a mask in crowded indoor settings, our study suggests that individuals can also potentially reduce their risk of getting COVID-19 or having poor outcomes by paying attention to their diet,” says co-senior author Dr Andrew Chan, MPH, a gastroenterologist and chief of the Clinical and Translational Epidemiology Unit at MGH.
The researchers also found a synergistic relationship between poor diet and increased socioeconomic deprivation with COVID-19 risk that was higher than the sum of the risk associated with each factor alone.
“Our models estimate that nearly a third of COVID-19 cases would have been prevented if one of two exposures – diet or deprivation – were not present,” says Merino.
The results also suggest that public health strategies that improve access to healthy foods and address social determinants of health may help to reduce the burden of the COVID-19 pandemic.
“Our findings are a call to governments and stakeholders to prioritise healthy diets and well-being with impactful policies, otherwise we risk losing decades of economic progress and a substantial increase in health disparities,” says Merino.
Study details
Diet quality and risk and severity of COVID-19: a prospective cohort study
Jordi Merino, Amit Joshi, Long Nguyen, Emily Leeming, Mohsen Mazidi, David Drew, Rachel Gibson, Mark Graham, Chun-Han Lo, Joan Capdevila, Benjamin Murray, Christina Hu, Somesh Selvachandran, Alexander Hammers, Shilpa Bhupathiraju, Shreela Sharma, Carole Sudre, Christina Astley, Jorge Chavarro, Sohee Kwon, Wenjie Ma, Cristina Menni, Walter Willett, Sebastien Ourselin, Claire Steves, Jonathan Wolf, Paul Franks, Timothy Spector, Sarah Berry, Andrew Chan.
Published in Gut in September 2021
Abstract
Objective
Poor metabolic health and unhealthy lifestyle factors have been associated with risk and severity of COVID-19, but data for diet are lacking. We aimed to investigate the association of diet quality with risk and severity of COVID-19 and its interaction with socioeconomic deprivation.
Design
We used data from 592 571 participants of the smartphone-based COVID-19 Symptom Study. Diet information was collected for the prepandemic period using a short food frequency questionnaire, and diet quality was assessed using a healthful Plant-Based Diet Score, which emphasises healthy plant foods such as fruits or vegetables. Multivariable Cox models were fitted to calculate HRs and 95% CIs for COVID-19 risk and severity defined using a validated symptom-based algorithm or hospitalisation with oxygen support, respectively.
Results
More than 3 886 274 person-months of follow-up, 31 815 COVID-19 cases were documented. Compared with individuals in the lowest quartile of the diet score, high diet quality was associated with lower risk of COVID-19 (HR 0.91; 95% CI 0.88 to 0.94) and severe COVID-19 (HR 0.59; 95% CI 0.47 to 0.74). The joint association of low diet quality and increased deprivation on COVID-19 risk was higher than the sum of the risk associated with each factor alone (Pinteraction=0.005). The corresponding absolute excess rate per 10 000 person/months for lowest vs highest quartile of diet score was 22.5 (95% CI 18.8 to 26.3) among persons living in areas with low deprivation and 40.8 (95% CI 31.7 to 49.8) among persons living in areas with high deprivation.
Conclusions
A diet characterised by healthy plant-based foods was associated with lower risk and severity of COVID-19. This association may be particularly evident among individuals living in areas with higher socioeconomic deprivation.
Diet quality and risk and severity of COVID-19: a prospective cohort study (Open access)
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