Diet and health have many links, including immune system function. Good nutrition supports the immune system to fight pathogens and helps to avoid chronic inflammation following an infection.
Many people know that vitamin C has significant effects on the immune system. Deficiency in the vitamin has associations with a higher risk of infections, such as pneumonia.
During the COVID-19 pandemic, interest in dietary supplements to support the function of the immune system has intensified. Although no specific food or supplement can prevent a person from contracting COVID-19, certain nutrients can help support the immune system’s function.
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A recent review has focused on the benefits of zinc against COVID-19. Zinc is a mineral found in many different food types.
The findings suggest that zinc could have protective effects against COVID-19 by supporting anti-viral immunity and reducing inflammation. A team of researchers at Sechenov University in Moscow, Russia, led the review and published it in the International Journal of Molecular Medicine.
Zinc is an essential mineral with a wide range of roles in the human body, including supporting the function of over 300 enzymes. The body needs zinc to carry out normal metabolism and ensure the proper function of the reproductive, cardiovascular, and nervous systems.
Foods high in zinc include animal products, such as meat, shellfish, chicken, and fortified breakfast cereal. However, beans, nuts, and seeds also contain zinc. Phytates in vegetables and grains can reduce the absorption of zinc and, therefore, vegetarians and vegans may need 50% more zinc in their diet.
Deficiency in zinc has associations with delayed growth in children, as well as increased risk of infection. It is also a significant risk factor for the development of pneumonia, which can be a consequence of COVID-19.
“According to the current estimates, the risk of zinc deficiency is observed in more than 1.5 billion people in the world,” explains lead author of the review Prof. Anatoly Skalny, who heads the Laboratory of Molecular Dietetics at Sechenov University.
“Given the crucial role of zinc in regulation of immunity, one can propose that its insufficiency may be considered as a risk factor for infectious diseases.”
– Prof. Anatoly Skalny
Together with colleagues in Russia, Germany, Greece, Norway, and the United States, Professor Skalny put together a review of the scientific evidence on zinc’s role in preventing and treating respiratory infections, including COVID-19.
Zinc supports the production and maturation of white blood cells, which are the major players in the immune system. There are multiple types of white blood cells, some of which make antibodies, capture and destroy pathogens, and return the immune system to normal after an infection.
Zinc also helps to regulate inflammation. While an inflammatory response is necessary to fight infection, the overproduction of pro-inflammatory cytokines early in the infection is responsible for some of the worst symptoms of COVID-19.
The review describes evidence showing that zinc may have an anti-inflammatory effect in pneumonia, limiting the damage to lung tissue.
For decades, scientists have known that zinc can block the replication of rhinoviruses responsible for respiratory infections in people, including the common cold.
Higher levels of zinc in cells help block the reproduction of rhinoviruses and stimulate interferon alfa production. This signaling molecule prompts nearby cells to initiate their anti-viral defenses.
The review also found evidence specific to coronaviruses. One study showed that zinc blocks the enzyme responsible for replicating the coronavirus that led to the SARS outbreak of 2002.
Interestingly, chloroquine — which some people suggested as a treatment option early on in the pandemic – increases the cells uptake of zinc, which may underlie some of its positive effects.
A 2020 study showed that when doctors treated patients with zinc and hydroxychloroquine, they discharged more patients, and fewer people died from COVID-19.
However, the paper suggesting that hydroxychloroquine or chloroquine could treat COVID-19 has since been retracted. The latest advice from the Food and Drug Administration (FDA) warns against using either of these drugs due to the risk of severe side effects.
The researchers also clarify that, although the evidence suggests zinc reduces the risk of respiratory diseases and their complications, there is not enough data to make recommendations regarding zinc intake and COVID-19.
It is also worth noting that consuming excess zinc can have adverse effects, including nausea, loss of appetite, and stomach cramps. Over the long-term, too much zinc has associations with low immunity. The National Institutes of Health provide daily recommended amounts of zinc.
