I generally take 1-2 grams of vitamin c daily. but i’ve seen many trials that were neutral to inconclusive as to the benefits of vitamin C.
that said, I’ve not had a cold many many years.
I do take about 10k iu of d3 plus k2.
Lately I’ve started taking two grams of b3 timed release niacin for my cardiovascular system. the time release makes it easy to do the high doses. You don’t get any benefit from the no flush version.
I take 5500 IUs of D3...................