Cells can turn off zinc absorption. Male prostate cells that are inflamed with BPH reduce their absorption about 20%. Prostate cancer cells reduce it approaching 80%.
Viruses in cells and cancer cells can play with the channels to protect themselves. When this happens, you benefit from a zinc ionophore.
In 2022 I was dealing with three loved ones with cancer. Did a lot of on line research. Found one study that looked at zinc content of 9 common cancers. All 9 had cancer cells/tumors deficient in zinc, even when surrounding normal tissue was rich in zinc. On of that team of researchers even suggested the possibility of using an ionophore with zinc as a treatment and a research study of same. This was late spring 2020. They were calling zinc a miracle drug, by September when they were doing some follow up, they had lost their enthusiasm for zinc. Had Fauci and company told them to shut up?
Another study I read said that Astaxanthin, which I have been taking for my cataracts caused cancer cells to die more quickly of old age (apoptosis), while encouraging normal cells to live longer. Was this slowing the rate of loss of those ends on genes (telemeres?) which causes old age?
Needless to say I immediately had my cancer sufferers on all 3 items—quercetin, zinc, and astaxanthin, in additon to their usual supplements.