The Star Late Edition

Malnutriti­on linked to Covid protection

- BURTRAM FIELDING and DEWALD SCHOEMAN Fielding is a professor and the director of research developmen­t at the University of the Western Cape. Schoeman is a PhD candidate in molecular biology and virology at the university.

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.

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