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I take both (D and zinc) and have for many years, and my experience is positive compared to the period before I started. Used to catch the seasonal colds and flus almost every winter, then stopped doing so. Allergies also reduced. However, I spend a fair amount of time outdoors too, so perhaps I am gaining more benefits from that. Also, even if you just think these things are healthful, that in itself can be a positive (attitude helps).
I also believe that reducing sugar in our diets has a considerable net positive effect on our health.
Not a complete ban, that might be overdoing it, but where practical substitute for sugar. I certainly get fewer headaches than before I made the switch, and can tolerate red wine which used to bring on headaches too.