sounds like zinc could be in high demand within the infected host. tends to be on the low side in ms patients, and the elderly, to start with. research and therapeutic trials with possibly transferable relevance:
can't get full text on this next 1976 study for the life of me, but i imagine the methods and results details would be telling...
- A double blind study of the effects of zinc sulfate on taste and smell dysfunction (1976)
https://www.ncbi.nlm.nih.gov/pubmed/797259
"...In the patient group prior to treatment, mean serum zinc concentration and leukocyte alkaline phosphatase activity were significantly lower than normal. Results indicate that zinc sulfate was effectively equivalent to placebo in the treatment of these disorders..."
- Causative factors of taste disorders in the elderly, and therapeutic effects of zinc (2008)
https://www.ncbi.nlm.nih.gov/pubmed/17592661
"RESULTS:
The incidence of taste disorders caused by drug administration and systemic disease were significantly higher in the elderly group. A serum zinc concentration of 69 microg/dl or lower was found in 33 per cent of the elderly group, significantly more (p < 0.001) than the 19 per cent of the 49 years or younger group with such a concentration. Zinc administration was therapeutically effective in 70 per cent of the whole population studied, and in 74 per cent of the elderly population.
CONCLUSIONS:
In the elderly, the incidence of taste disorders caused by drug administration or systemic disease was significantly greater compared with other age groups. The curative effects of zinc administration were not observed to be influenced by age."
and that's with 34 mg daily supplemental elemental zinc, over at least 3 months, with mean serum levels rising only into the 90s in mg/dl. i wonder what the therapeutic efficacy stats would have been with higher mean serum zinc levels achieved, either via a higher daily dose or longer zinc administration.
- Importance of zinc in the elderly: the ZENITH study (2005)
fft https://www.nature.com/articles/1602286
"Zn and immunity
With advancing ageing, there is a progressive decline in immune responses. Changes associated with ageing may be partly related to Zn deficiency, which induce comparable impairment of the immune response (Dardenne, 2003)..."
and now to the liver:
- Dysfunction of the liver affects the sense of smell (2005)
https://link.springer.com/article/10.10 ... 004-0303-x
"Nearly all patients had low serum zinc levels with a mean of 0.50 mg/l and a range of 0.28–1.1 [normal range: 0.7–1.3 mg/l], regardless of etiology or stage of cirrhosis. Only four patients had normal zinc levels. ... Neither zinc nor bilirubin correlated with measures of olfactory function (zinc: r35 = < 0.11, p > 0.54; bilirubin: r45 = < 0.27, p > 0.07) ...
zinc levels did not correlate directly with measures of olfactory function. In fact, only four patients had normal zinc levels – but only one of these also had normal olfactory function; two were hyposmic and one had functional anosmia. While administration of zinc may improve olfactory function, just as zinc improves hepatic encephalopathy [28, 29], the benefit of zinc in the therapy of olfactory impairment is controversial."
okay so simply achieving 'normal' may not be good enough. got it. and we are referred to the 1976 study mentioned above, for which we know details of methods and results may be telling, if we could only get at those details. which we can't. or at least *i* can't. moving on:
- Associations between Zinc Deficiency and Metabolic Abnormalities in Patients with Chronic Liver Disease (2018)
https://www.mdpi.com/2072-6643/10/1/88
"...The liver mainly plays a crucial role in maintaining systemic Zn homeostasis..."
and to the liver x aging
- Changes in regulation of human zinc metabolism with age (1992)
https://www.ncbi.nlm.nih.gov/pubmed/1443235
"...During zinc loading, response (defined as change from basal state) of plasma zinc concentration, urinary zinc excretion, and liver zinc increased with age, while response of fraction of zinc taken up by red blood cells decreased with age..."
not forgetting:
very informative abstract here ^, but i disagree with using 60 as a lower cutoff and i wouldn't consider mean 68 mg/dl good enough to leave supplementation out of the mix. recall the supplemental zinc regimen noted earlier, which brought subjects' mean levels up into the 90s in mg/dl with only partial therapeutic efficacy (70% is still good, but could it have been even better??)
- Correction of hypozincemia following liver transplantation in children is associated with reduced urinary zinc loss (1999)
https://www.ncbi.nlm.nih.gov/pubmed/10051486
"...After transplant, there was a significant reduction in urinary zinc losses in the hypozincemic group followed by normalization of plasma zinc levels by 7 days posttransplant."
- Micronutrient Levels and HIV Disease Status in HIV-Infected Patients on Highly Active Antiretroviral Therapy in the Nutrition for Healthy Living Cohort (2006)
https://journals.lww.com/jaids/fulltext ... in.15.aspx
"Forty percent of men and 36% of women had low zinc, however. Subjects in the upper quartiles of zinc had lower log HIV viral load levels... Decreased retinol levels in women and in men with CD4 counts >350 cells/mm3 and increased zinc and selenium levels in both genders may be associated with improved virologic control."
- Safety and efficacy of zinc supplementation for children with HIV-1 infection in South Africa: a randomised double-blind placebo-controlled trial (2005)
https://www.sciencedirect.com/science/a ... 3605677562
"Zinc supplementation of HIV-1-infected children does not result in an increase in plasma HIV-1 viral load and could reduce morbidity caused by diarrhoea... Programmes to enhance zinc intake in deficient populations with a high prevalence of HIV-1 infection can be implemented without concern for adverse effects on HIV-1 replication. In view of the reductions in diarrhoea and pneumonia morbidity, zinc supplementation should be used as adjunct therapy for children with HIV-1 infection."
- A tug-of-war between severe acute respiratory syndrome coronavirus 2 and host antiviral defence: lessons from other pathogenic viruses (2020)
https://www.tandfonline.com/doi/full/10 ... 20.1736644
"The severe cases present with pneumonia, which can progress to acute respiratory distress syndrome..."
a nuance to consider:
- Effect of Zinc Sulfate on Sensorineural Olfactory Disorder (1998)
https://www.tandfonline.com/doi/abs/10. ... 9850182936
"...For disorders of post-viral and unknown aetiologies, there were no significant differences in improvement among the three groups... for post-viral olfactory disorder, the lack of olfactory receptor cells and blast cells due to viral infection results in loss of regenerative capacity...
...After January 1993, we began administration of zinc sulfate 300 mg/day to patients for more than one month...
so 68 mg per day, noting 220 mg of zinc sulfate contains 50 mg of elemental zinc
https://ods.od.nih.gov/factsheets/Zinc- ... fessional/
continuing from same article:
- Table II. Mean pre-treatment serum zinc concentration by aetiology and outcome (mg/dl)
the means in Table II are all low normal regardless of aetiological group. mostly in the 70s, at best in the 80s,
Fig 4 caption: "Schema of the difference between lesions in post-viral and post-traumatic olfactory disorder. In post-traumatic olfactory disorder, olfactory nerve and receptor cells are damaged, while some blast cell remain intact. In post-viral olfactory disorder, both receptor cells and blast cells are damaged."
so. sounds like preventive levels going in may be the order of the day.
as to that, we know that zinc is essential, but toxic in excess. the above makes me wonder if the studies showing anosmia after intranasal zinc spray damaged blast cells in some way.
in the study below, where lung function is concerned it looks like serum zinc levels above 150 mg/dl are consistently changing the slope of the line of best fit for the worse.
(link stopped working but fig 2 is easily viewed via the full text link above)
all in all, zinc could come in handy vs covid-19 initial infection, vs pneumonia in severe cases and maybe even vs the less frequently experienced diarrhea. the challenge will be to get enough, without excess, when testing may not be readily available.