From an article in The American Journal of Clinical Nutrition, under the title "Zinc and immune function: the biological basis of altered resistance to infection":
Zinc is known to play a central role in the immune system, and zinc-deficient persons experience increased susceptibility to a variety of pathogens. The immunologic mechanisms whereby zinc modulates increased susceptibility to infection have been studied for several decades. It is clear that zinc affects multiple aspects of the immune system...
Zinc is crucial for normal development and function of cells mediating nonspecific immunity... The effects of zinc on these key immunologic mediators is rooted in the myriad roles for zinc in basic cellular functions... This review explores these aspects of zinc biology of the immune system and attempts to provide a biological basis for the altered host resistance to infections observed during zinc deficiency and supplementation. https://pubmed.ncbi.nlm.nih.gov/9701160/
And here is a frame from a video from India, which cheerfully reports the banning of all at-home treatments of Covid-19, including zinc. Federal health authorities, after great international pressures, had complied, rejecting everything except for the most expensive medication, remdesivir.
A success as total as this, had not been easy to obtain for Pharma and the WHO, since India is a powerful country, and has a major pharmaceutical industry. India produces ivermectin and was now a most difficult terrain on which the WHO could battle against incorrect thinking.
The reason for the difficulty was that the Indian state of Uttar Pradesh, 230,000,000 inhabitants, had recently been suffering in a terrible covid epidemic. Then the state authorities had sent out some 70,000 teams to distribute medical kits including ivermectin, to the farthest village of the state. The state had soon ended the epidemic, obtaining the congratulations of the WHO, which did not mention the content of the medicinal package. Other Indian states, even much smaller, like Kerala, about 30M, complied with orders, rejecting all effective cures.
The answer of Indian doctors: they continued prescribing ivermectin.
Zinc
Zinc is released from food as free ions during digestion. These liberated ions may then bind to endogenously secreted ligands before their transport into the enterocytes in the duodenum and jejunum.[6,10] Specific transport proteins may facilitate the passage of zinc across the cell membrane into the portal circulation. With high intakes, zinc is also absorbed through a passive paracellular route. The portal system carries absorbed zinc directly to the liver, and then released into systemic circulation for delivery to other tissues.
...The potential interaction between iron and zinc has been a cause of concern. Solomons and Jacob[40] found that high doses of inorganic iron decreased zinc uptake as measured by changes in plasma zinc over the next 4 h after an oral dose. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3724376/
Toxicity
Although zinc is an essential requirement for good health, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption.[201] The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish.[227] The Free Ion Activity Model is well-established in the literature, and shows that just micromolaramounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93% of all Daphnia in water.[228]
The free zinc ion is a powerful Lewis acid up to the point of being corrosive. Stomach acid contains hydrochloric acid, in which metallic zinc dissolves readily to give corrosive zinc chloride. Swallowing a post-1982 American one cent piece (97.5% zinc) can cause damage to the stomach lining through the high solubility of the zinc ion in the acidic stomach.[229]
On September 23, India’s apex medical research body, the Indian Council of Medical Research (ICMR), revised its ‘Clinical Guidelines’ for COVID-19. Specifically, it removed mention of two drugs that a panoply of experts and non-experts had widely used and promoted both in India and worldwide, and which had also been ceaseless sources of controversy: ivermectin and hydroxychloroquine (HCQ).
The previous version of the national COVID-19 treatment protocols, dated May 17, 2021 (the one from which ICMR dropped the use of convalescent plasma) suggested that ivermectin and HCQ “may” be used despite “a low certainty of the evidence”. This feeble cautionary note did nothing to dampen the ill-founded enthusiasm for the use and promotion of both drugs. https://science.thewire.in/health/icmr-revises-covid-treatment-guidelines-removes-ivermectin-hydroxychloroquine/
Poisoning
In 1982, the US Mint began minting pennies coated in copper but containing primarily zinc. Zinc pennies pose a risk of zinc toxicosis, which can be fatal. One reported case of chronic ingestion of 425 pennies (over 1 kg of zinc) resulted in death due to gastrointestinal bacterial and fungal sepsis. Another patient who ingested 12 grams of zinc showed only lethargy and ataxia (gross lack of coordination of muscle movements).[235] Several other cases have been reported of humans suffering zinc intoxication by the ingestion of zinc coins.[236][237]
Pennies and other small coins are sometimes ingested by dogs, requiring veterinary removal of the foreign objects. The zinc content of some coins can cause zinc toxicity, commonly fatal in dogs through severe hemolytic anemia and liver or kidney damage; vomiting and diarrhea are possible symptoms.[238] Zinc is highly toxic in parrots and poisoning can often be fatal.[239] The consumption of fruit juices stored in galvanized cans has resulted in mass parrot poisonings with zinc.[63]
In the joy and excitement of giving up their allegiance to dark forces of ignorant anti-science, the ICMR decided to give up all of Satan's pomps, including vitamin C and vitamin D and zinc. They were greatly relieved afterwards, since the order was probably issued in response to solid financial offers, or in a fair exchange for important positions with the WHO or with Pharma.
There had to be sufficient threats and inducements brought to bear on medical authorities, to cause them to issue orders to drop ivermectin, orders certain to be welcomed with great relief, by the authorities who had rejected ivermectin and were suffering an awful level of illness and mortality, in the Indian states of Tamil Nadu and Kerala.
The same orders, in the states of Goa, Uttar Pradesh, and Dehli, where ivermectin had been distributed ad where the epidemic was over, were welcome with contempt, by doctors, pharmacists, and patients.
Since the authorities were willing to face shame and contempt, they thought that by banning vitamin C, vitamin D, and zinc as well, they would show total submission to Washington and Geneva.