I am on the other side from most here and have convinced myself that it is my long time regimen of vitamin supplements that keeps me from catching whatever's going around. Could be mental and I've been accused of that before.
One thing you should do with any vitamin, put it in white vinegar and watch for the dissolve time. You could just be passing some through. It should immediately start to break down as that most resembles the PH of stomach acid.
I take: NewChapter Every Man's Multi 40+ (they have a 50+ but I want to keep my 40 year old brain), C, D3, Flaxseed Oil, Fish Oil, B-12, Cinnamon, Turmeric Curcumin, Lutein, Osteo Bi-Flex, Magnesium and Tru-OPC for vascular eye health and Magnesium, all that in the AM and Potassium in the PM along with Fish Oil, Turmeric Curcumin and another Osteo.
I cannot argue the value of supplements for anyone else but I have proof that Magnesium and Potassium stopped my nighttime leg cramps and Tru-OPC's stopped the blood vessels from bursting in my eyes.
The Turmeric Curcumin and Osteo are for joints and while I have a bad back and hip, I am convinced it would be worse without that every day.
It is a pain in the butt to take 15-18 vitamins a day and is expensive but I have sold myself on this. I also am a drinker and cigar smoker and need something to counter the evil effects on my person with my vices but I love my vices, they are mine, all mine!. I am convinced my vitamins could be Marvel heroes.
Vitamin supplements, like alcohol and coffee, bounce around with medical recommendations and I laughed at one group of researchers stating we should be getting all of the necessary vitamins from our diet. Americans have the worst diet of any developed country in the world. And I am no exception to that so I try to achieve balance.