High-quality, plant-based foods linked with lower COVID-19 risks, reveals ZOE analysis

07 Sep 2021 --- People who eat high-quality, gut-friendly diets with plant-based foods are less likely to develop COVID-19 or become severely ill. This is according to an analysis of nearly 600,000 ZOE COVID Study app contributors, which the researchers say is the largest study in this space.

“These data highlight the importance of diet quality on health – not just calories and fats,” Tim Spector, lead scientist at ZOE COVID Study and professor of genetic epidemiology at King’s College London, UK, tells NutritionInsight

Diet quality is an established risk factor for many conditions that are known to have an inflammatory basis, adds Andrew Chan, a gastroenterologist and director of epidemiology at Massachusetts General Hospital and professor at Harvard Medical School. 

“Our study demonstrates that this may also hold true for COVID-19, a virus that is known to provoke a severe inflammatory response.” 

In March 2020, health science company ZOE launched an app that allows US and UK users to record various lifestyle markers like diet, along with COVID-19 factors. With 4 million global contributors, the scale of this data allows researchers to adjust for multiple confounding factors. 

The effect of diet on COVID-19 is independent of other known risk factors, including age, weight, ethnicity and underlying health conditions, but was amplified by social inequality.

Pinning down high-quality diets
It had not yet been clear how diet affects the risk of catching the virus independently of factors like obesity and diabetes. Based on analysis of symptoms or PCR test results reported in the app, 31,815 contributors (19 percent) ultimately caught COVID-19. Notably, people with the highest quality diet were around 10 percent less likely to develop COVID-19 than those with the lowest quality diet and 40 percent less likely to fall severely ill.

These diets include plant-based foods such as fruits, vegetables, whole grains and nuts, as well as oily fish, healthier fats like olive oil, less processed foods and refined carbohydrates. 

In contrast, a low diet quality score is associated with diets high in ultra-processed foods and low amounts of plant-based foods, like fruit and vegetables.

Plant-based perks
According to ZOE, recent research on a smaller cross-sectional sample has shown that people who eat a plant-based or pescatarian diet are less likely to become severely ill with COVID-19. However, this is the first study to show that a healthier diet actually reduces the chances of developing the disease in the first place.

“You don’t have to go vegan, but getting more diverse plants on your plate is a great way to boost the health of your gut microbiome, improve your immunity and overall health, and potentially reduce your risk from COVID-19,” says Spector.

The analysis also found that high-quality diet scores were also linked with a healthier and more diverse gut microbiome. This was also associated with a wide range of favorable health outcomes, including reduced inflammation and body fat and improved levels of blood lipids and glucose.

For this reason, higher quality scoring diets were also referred to as “gut-friendly” diets. 

“The ultra-processed foods eaten by 60 percent of US consumers is harming our immune systems and microbes. This makes us more susceptible to COVID-19 and other conditions from obesity to dementia. The gut microbes are the key link between our food and our immune systems,” emphasizes Spector.

Social factors take a toll
Notably, the relationship between diet quality and COVID-19 risk still remained after accounting for all potential confounding factors. Factors included age, body mass index (BMI), ethnicity, smoking, physical activity and underlying health conditions. Mask-wearing habits and population density were also considered.ZOE’s app provides insight on asymptomatic and symptomatic information across the UK, with 1.2 million logging on a weekly basis.

However, the impact of diet was amplified by individual life situations, with people living in low-income neighborhoods and having the lowest quality diet being around 25 percent more at risk from COVID-19 than people in more affluent communities who were eating in the same way.

Therefore, the researchers estimate that nearly a quarter of COVID-19 cases could have been prevented if these differences in diet quality and socioeconomic status had not existed. 

This further highlights that improved access to nutritious, healthier food could be substantive for bettering public health, especially among the underprivileged members of the community, they argue. 

Spector also notes that there were no major differences between the US and UK cohorts in terms of the relationship between diet and COVID-19. 

“Both countries have similarly poor diets so not surprising they are similar. However, the effect of diet quality even after adjusting for body weight and deprivation and other conditions was larger than I expected.” 

Access to healthier food is essential
COVID-19 has laid bare how such social determinants underlie the severe racial and socioeconomic disparities in COVID-19 risk that we and others have documented, emphasizes Chan. 

“Access to healthier food is important to everyone in society, but our findings tell us that helping those living in more deprived areas to eat more healthily could have the biggest public health benefits,” adds Dr. Sarah Berry, study co-lead and reader in nutritional sciences at King’s College London. 

In April, another analysis based on the ZOE COVID Study app found that women taking certain supplements are less likely to test positive for SARS-CoV-2. An earlier assessment also revealed that supplementation of probiotics, omega 3 fatty acids, multivitamins or vitamin D was associated with a lower risk of self-reported SARS-CoV-2 infection.

By Katherine Durrell