Malnutrition linked to Covid protection
IN OUR recent paper we explore the possible links between Sars-CoV-2 infection, Covid-19 disease and nutrition. Severe malnutrition is the most prevalent cause of immunodeficiency in the developing world.
We focused on malnutrition that leads to deficient levels of leptin, such as is seen in protein energy malnutrition, a deficiency of dietary protein despite sufficient calorie intake.
Protein energy malnutrition is a global issue, and while the condition has decreased in Asia, African nations have reported a continued increase. Leptin is a hormone that is made in the fat cells of the body and has multiple roles in the immune system.
Leptin deficiency caused by malnutrition does not protect a person from infection by the coronavirus causing Covid-19. But, based on the work of others in molecular medicine and immunology, we suggest it might counteract the harm caused by the excessive inflammation that occurs with Covid-19 disease.
Leptin increases the body’s response to inflammatory cytokines – proteins that regulate inflammation. Overweight Covid-19-positive patients tend to have higher leptin levels. And high leptin levels are associated with severe Covid-19. Therefore, the impact of leptin on the immune system and its correlation with Covid-19 progression and severity could also make it a valuable biomarker, for predicting patient outcomes.
We know that malnutrition has been linked to changes in the immune system – this is especially so with protein energy malnutrition.
The immune system of people with a balanced nutritional intake responds to infection by releasing cytokines. These are signalling molecules that instruct the immune system to attack invading microbes. Most commonly, the attack takes the form of inflammation. Once the invading microbes are eliminated from the body, the inflammation disappears and the body returns to normal. The careful balance of activation and deactivation of the inflammatory response is crucial for normal functioning of the body.
In many severe Covid-19 cases the immune system produces a surge of cytokines. This causes a prolonged hyper-inflammatory response that does more harm than good.
In people with low leptin levels, such as those with protein energy malnutrition, the immune system produces more anti-inflammatory cytokines and fewer inflammatory ones. This shift in the immune response in favour of an anti-inflammatory profile would, in theory, counteract the dire consequences of the hyper-inflammatory response often seen in severe Covid-19 cases, where the patient’s organs can be damaged.
But it’s also possible that this anti-inflammatory response could mask the symptoms of malnourished people infected with Covid-19. They might appear to have a mild to moderate cold rather than Covid-19. This means that the true number of Covid19 infections could be underestimated and could contribute to transmission of the disease because people don’t know they are infected.
We theorise that deficient leptin levels caused by malnutrition might protect against severe Covid-19 and related death. This could be a reason why we are seeing lower than expected Covid-19 deaths in Africa. But even if this is true, we should not ignore the fact that malnutrition is killing millions and we should not curb efforts to eliminate food insecurity globally.