Is Vitamin C enough?

I take between 8 and 12 grams of Vitamin C per day spaced 2-3 times throughout the day. If I feel a tickle in my throat I immediately take 4 grames and repeat every 30min or 1 hr until I feel it go away or I get bowel symptoms. In general I feel this has helped ward off many colds HOWEVER twice in the past two weeks this regime has not been enough. Why is this regime not enough and why does my husband who never takes supplements or even eat fruit never get a cold?? Tweet