Why the inflammation triggered by what you eat may be putting you at risk from COVID-19 ‍

One of the biggest mysteries about the COVID-19 pandemic has been why some people are seriously affected or lose their life to coronavirus, while others have only mild symptoms or none at all.

As we’ve discovered through analysing data from millions of users of our COVID Symptom Study app, being seriously overweight (obese) can significantly increase the chances of ending up in hospital with COVID-19, even for people who are otherwise young and healthy. And other diseases linked to diet, including diabetes and cardiovascular disease, also increase the likelihood of becoming severely ill with coronavirus.

Scientists are now starting to suspect that some of the links between obesity and increased risk from coronavirus may be related to how our bodies process sugar (glucose), particularly because high blood glucose levels have been associated with inflammation and faulty immune responses seen in people with serious COVID-19.

We caught up with expert Dr. Ana Valdes, associate professor at Nottingham University, to find out more about the connection between diet, weight, inflammation and COVID-19. ‍

Taking a closer look at the link between COVID and obesity‍

Data from our COVID symptom study has confirmed that people who are very overweight are more likely to suffer the dangerous effects of coronavirus. 

"What we see with COVID is that people with obesity are at much higher risk than people with conditions like asthma. That is not what you see with things like flu, so that is a bit surprising," says Ana. 

Ana thinks that how our blood sugar levels change after eating might be vital to understanding why some people have dysfunction immune responses to the virus, resulting in severe inflammation and life-threatening symptoms. Even identical twins, who share 100 per cent of their genes, can have very different nutritional responses, potentially explaining some of the reason why people can also have different responses to coronavirus infection.

“This virus and other coronaviruses such as SARS and MERS interact with the immune system in a way that puts people who have a particular type of nutritional response to glucose at a much higher risk because they do not mount an effective immune reaction against the virus,” Ana explains.‍

A study of patients in Wuhan, China, showed that patients’ blood sugar levels when they arrived in hospital with COVID-19 predicted how likely to die from the disease, with people with the highest blood sugar levels being most at risk.‍

Further data from the US also shows a link between high blood sugar levels, inflammatory responses to COVID-19, and disease progression in patients both with and without diabetes.

“That is telling us a lot because it means that glucose is a key component to the immune response that the body mounts against COVID-19,” she adds.‍

How your blood sugar impacts your response to COVID ‍

So what might be going on here?

“Normally, a healthy cell uses oxygen to transform glucose into energy,” Ana explains. “It's a very efficient process called aerobic respiration.”

Sometimes, if your blood sugar levels are high for a long time, you can begin to suffer from inflammation. Your cells can start converting glucose using an inefficient, anaerobic method. 

"This high glucose, anaerobic state can make your immune cells respond in an inflammatory way,” says Ana.  

For your immune system to function correctly and protect your body from viruses like SARS-CoV-2, it must strike a balance between inflammatory immune responses that help to protect and heal and anti-inflammatory responses that keep a lid on potentially dangerous overreactions.

Research suggests that high blood sugar levels can increase the number of inflammatory immune cells and suppress the anti-inflammatory cells, throwing the immune system out of balance. Too many inflammatory immune cells can result in a cytokine storm, an out-of-control immune overreaction that has been seen in many people who have died with COVID-19. 

Several studies have also shown that people of BAME (black, Asian, and minority ethnic) descent are at increased risk of the deadly effects of COVID-19. 

Ana believes that this may be due to differences in glucose metabolism between different ethnicities. For example, African Americans are 60 per cent more likely to be diagnosed with type 2 diabetes than non-Hispanic white people. And people from South Asian communities are up to 6 times more likely to have diabetes than the general population.‍

Using data to understand the relationship between blood sugar and immune response‍

Although unhealthy blood sugar responses are associated with being overweight, Ana explains that you could still have unhealthy metabolic responses and be at increased risk from COVID, even if you are at a healthy weight. 

“There is scope to investigate how diet can modulate immune responses and how we can use diet to improve the immune system. It's not like you have to lose a certain number of pounds to be in better shape to fight the virus. It is about whether you can make dietary choices that will put your immune system in a better position to fight the virus,” Ana explains.‍

The bitter truth about blood sugar, weight and COVID-19

• Data from our COVID Symptom Study has highlighted a link between obesity and severe symptoms of COVID-19. 
• Our scientists believe that some of the links between obesity and increased risk from COVID-19 may be related to how our bodies process glucose (sugar). 
• High blood glucose levels have been associated with inflammation and harmful immune responses, similar to those seen in people with serious COVID-19.
• Our experts believe that healthy food choices that are right for your personal metabolism can improve your blood sugar responses, help your immune system to function correctly, and potentially reduce your risk from COVID-19. 
  

Find out more:

• Is being overweight a COVID-19 risk? – COVID Symptom Study
• The trinity of COVID-19: immunity, inflammation and intervention – Nature Reviews Immunology 
• Elevation of blood glucose level predicts worse outcomes in hospitalized patients with COVID-19: a retrospective cohort study – BMJ Open Diabetes Research & Care 
• Glycemic Characteristics and Clinical Outcomes of COVID-19 Patients Hospitalized in the United States – Journal of Diabetes Science and Technology
• COVID-19 cytokine storm: the interplay between inflammation and coagulation – The Lancet Respiratory Medicine 
• Ethnic and socioeconomic differences in SARS-CoV-2 infection: prospective cohort study using UK Biobank – BMC Medicine
• What happens when you eat? – ZOE 
• PREDICT findings from the American Society of Nutrition - ZOE