Zinc is a building block. And should not be taken in high doses. Vitamin C when used to fight infection should be taken in much higher doses. You should not NOT take these higher doses with anything other than pure vitamin c. Vitamin C strips the lipid layer off viral particles and allows your body to attack the now recognizable particle. To acheive this blood concentration you'd have to be taking at least a gram every hour. Your body processes vitamin C quickly so taking it every hour is a must when you are sick, otherwise you're not utilizing the vitamin c to fight infection. Any improvement you have felt is likely due to the zinc you are taking and not the vitamin C. To utilize vitamin C to fight infection, you must reach bowel tolerance and stay there until symptoms subside. When I get sick I can feel when I need to take more vitamin c, usually about every 45 minutes for me.