I won't comment on the vitamins as my knowledge these days is limited, and I'm not interested enough to dedicate time to such. but I have been on the hook of the vitamin literature too - it was quite fashionable in my younger years and experimenting with vitamins was cheap in those days.
but you read like a person worried for their health. are you worried?
most people are.... I did a spot of research on stress many years ago. Hans Selye defined stress in a holistic sense and since that breakthrough the effects of worry became the focus in a lot of different disciplines, among which was immunology.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1361287/ is a met-analysis of more the 300 studies relating the immune system effects.... you might find it interesting. I first got interested in the description of cancer survivors using meditation (stress reduction techniques and much more) to stimulate the immune system. macrophages are the key here as they wander throughout the body picking up cancer cells and remove them.
honestly square pants there is a lot of good advice in scientific literature.
