I don't know,but for me, I always buy the vitamin C pills with low dosage (250mg), so I can separate the dose to 2 or 3 times a day. Vit C is water soluble so we can easily lose them via urine. If taking 1000mg Vit C at once, I'll probably lose most of them within hours.

But then, I contradict myself; cause whenever I feel the sore throat and impending sickness, I will drink Redoxon/Sandoz (which are high dosage). I'll feel better after that.

Of course, I believe that getting Vit C from fresh vege and fruits are the best way, but I can't seem to get enough from them. Probably because Vit C oxidized too quickly when we cut the fruit? I do feel a difference between the months when I take vitamin C and not taking it. I get less sickly and skin is better. But that's for me only. Maybe other people have other experience.