Zinc and Immunity
Zinc is known by many Consumers to have immune properties. ref ref There are zinc lozenges that might help fight off the cold causing virus, the rhinovirus. Zinc is also given out in Africa by clinicians who only see children once a month to help prevent bacterial diarrhea from unsanitary living conditions. 
Zinc is also known to help wounds heal faster, such as after surgery. The web is awash with many other positive uses for zinc. ref ref Plus, now there are even new articles that say zinc will inhibit the growth of the coronavirus. Thus, many nutritionists and vitamin companies are recommending it. Is Zinc a miracle worker, or is there more to the story? ref
FYI: Zinc is a water soluble mineral and needs help getting past the cell fat membranes and into cells. There are zinc protein carriers to facilitate this transferinto cells as well as ionophores in foods and supplements such as quercetin, ref, and in drugs such as the anitmalaria drug hydrochloroquine. Both zinc and an ionophore are necessary since it is not yet known how to increase zinc protein carriers. ref
There is more to the story indeed. Yes, zinc in test tube research stops cornoavirus plus other viruses. And live studies show positive effects on some types of virus caused diseases. But, there is another fact that only scientific researchers must be aware for zinc. This aspect is nowhere to be found in the media or in virus website recommendations. One of the symptoms associated with COVID-19 disease is a loss of taste and smell. These are classic signs of a zinc deficiency or zinc balance disruption. SARS-CoV-2 viruses use up zinc to form part of their structure. Over time, the genetic code of many viruses have adapted to manipulate zinc balance so more is available for virus growth and less for boosting immune system elements to stop viruses.
Zinc is the dominate metal ion out of a few possible choices that viruses use to attach to their protein structure during viral replication in cells. Scientists are looking into ways to inhibit this process by using elements that bind up zinc so it is no longer available for this building virus activity.
QUESTIONS: How do zinc supplements at different amounts influence immunity versus viral replication? Do zinc supplements even have any effect on the free zinc levels inside cells since the controlling mechanism is tightly requlated to only allow small amounts inside cells? article Of note: in test tube studies, zinc is most effective at early stage of virus attack.
Zinc occurs in two forms in the body. Some Zinc is chelated or combined with a protein and the rest is unbound as free ions. It appears that the free form is the active form. Inside cells, the level of free zinc is highly regulated to just tiny amounts for a very sound reason. While zinc helps build over 300 enzymes to make different protein structures for vital cell functions, there is another use that deserves attention. Since zinc helps build proteins, this function may be hijacked by viruses to HELP build more viruses, and zinc is the preferred metal ion placed by this new coronavirus in it's cap over the protein RNA material. ref
The bound form of zinc may play an opposite role to the free zinc form and these actions are probably balancing. ref ref The free zinc works as a signal messenger for the immune system. Both low amounts as well an excess of free zinc can exhibit adverse effects on cells. This appears very complicated, but this is similar to the way a few other nutrients also function. Vitamins like folic acid and vitamin B6 can also function in opposite directions at different amounts, plus also at different stages of body or disease processes.
Vitamin D first dissolves bones to release calcium to balance levels in the blood. At the same time, vitamin D also directs bone building cells to get to work replacing the bone that were just dissolved. Funny how nature works sometimes. BUT, the proper use of vitamin supplements has to account for these many different actions to maintain balance. The bottom line is this: Zinc is vital within a given range of dosages. Both too little and too much are detrimental. And perhaps the greatest need is to help the body control zinc forms. Certain drugs work in this area but there are also supplements and foods that contain nutrients using thses same actions. Quercetin is one. These nutrients have elements that can bind up zinc for future use.
How Zinc Unwittingly Helps Viruses Grow
This reference is easy to read and follow. It shows how viruses can hijack body functions for their own selfish reasons. It deals with a very complex process of regulation. Zinc plays roles in many different body areas and immune processes. One significant action is to build IT-2 that increases T-cell immune cell numbers if low.
Supplement zinc at only about 15-20 mg. Maybe up to 30 mg. for certain groups, like seniors and vegetarians. A small subset of Seniors will need slightly more , 40-50 mg., since digestive or compromised digestional disturbances hinder uptake. Three months tends to max tissue saturation. Government max amount is 40mg. The body begins to decrease zinc absorption percentage with continued supplements. The diet also supplies some if not most. Check out list of food sources for zinc amounts to see how many of the foods are in your diet, or if you consume whole grains and beans that have phytates which hinder absorption. ref Then, supplement wisely if and when needed.
It is not yet known how to properly maintain the unbound levels of zinc in cells. Zinc ionophores such as quercetin may be one answer. Body wisdom hopefully should and has to suffice. Studies have shown that if zinc is low, supplements help correct. What is not well known, if levels are already sufficient, what does extra do to zinc functions. Too much is also not desirable but generally this is found with 75+ mg. as discovered from the first AHREDS study on vision. Maybe there are also subtle effects at 50+ mg. Other minerals might be impacted such as copper and also some minerals like iron and calcium could limit zinc absorption too. Best to take zinc (with a tiny amount of copper) separately.
Check back for more information. This information should give some clarity to evaluate when reading scientific studies or nutritional recommendations.
Zinc and Cell Membranes
The other area of zinc influence is at the cell membrane area. Zinc helps form barriers in cell membranes to attempt to limit virus penetartion into the cell. This area will get more information soon. Where zinc interacts inside cells. ref Next is copy from the summary of last referenced study.
"Since Zn (zinc) and Zn ionophores interact with both the autophagy machinery and the replicative apparatus in SARS-CoV, such interactions likely involve ER stress and UPR induction.
UPR = unfolded protein response
Autophagy = body cleaning out damaged cells
ER stress = Endoplasmic reticulum stress. - Cell life and death decisions
ER disturbances can lead to conserved cell stress response, the unfolded protein response, which first tries to mitigate damage in cell, but if too great, triggers cell death.
In summary SARS-CoV-2 can possibly activate UPR and hijack this pathway for the benefit of its own infection process. In Scheme 1 a brief summary of the possible role of autophagy and UPR in SARS-CoV-2 infection is summarized. Considering that the replication of coronaviruses causes ER stress and induces UPR in the infected cells, additional research on coronavirus-induced UPR could help identify new targets for antiviral agents and facilitate the development of effective vaccines against covid-19. Interfering with or manipulating the coronavirus-induced UPR may provide new therapeutic targets that contribute to infection control and the pathogenesis of this emergent coronavirus."
NEW STUDY on Covid-19 and 4 nutrients, Quercetin, Zinc, Bromelain, and Vitamin C now starting here.