I don’t think there’s great scientific evidence to back up advising the population to start taking vitamins and sleeping on their stomachs (I have never heard this).
My DH was in ICU with covid. The nurses kept me updated and one of the things they reiterated was 'sleep prone'. Keeping him prone was vital. However he could not sleep prone because he is morbidly obese, so they kept him on his side which was better than keeping him supine.
Here is your scientific evidence:
www.ncbi.nlm.nih.gov/pmc/articles/PMC7402434/
Zinc= big time immune system booster
Vitamin D3... the jury is still out on this one, however, there is a correlation between ICU admissions and covid patients suffering vitamin D3 deficiency.
DH's morbid obesity, however, played an enormous role in his severe symptoms and hospital admission. This does not mean that I am saying thin, healthy people don't die of covid. But DH noticed himself that every single patient in his bay was obese, like him.
Again, your scientific evidence to back up my claim:
"Obesity causes mechanical compression of the diaphragm, lungs, and chest cavity, which can lead to restrictive pulmonary damage. Furthermore, excess fat decreases total respiratory system compliance, increases pulmonary resistance, and reduces respiratory muscle strength"