A complete discussion of the "discontinuation effect" (sometimes called the rebound effect) was here, may still be here, otherwise I'll try to find it for the archives.
In a nut shell, the Bowel Tolerance forum - and the http://www.orthomed.com/titrate.htm
paper by Cathcart helps people determine what the right amount of vitamin C is for themselves. The answer is somewhere between 4000 mg and 20,000 mg, spread out 4 times throughout the day.
Most people live in a state of vitamin C starvation. A good analogy is the body's response to little water in a desert, the body begins to hold on to its water during periods of dehydration.
Vitamin C is handled in the same way. The body holds on to what little it can get. But, when the supply is ample - such as the case with most animals producing 24/7 - the body no longer needs to horde vitamin C and various enzyme systems begin that transform ascorbate into other substances.
If the supply is then suddenly cut off, these enzyme systems still transform C for 24 to 48 hours, and this is the discontinuation effect. It is not known to be serious, but a cold or congestion is likely.
Pauling recommended not stopping vitamin C even for a single day. I agree. But you can also lower the dosage slowly to avoid this effect.
Owen R. Fonorow, Orthomolecular Naturopath
My statements have not been evaluated by the Food and Drug Administration. Any product mentioned is not intended to diagnose, treat, cure or prevent any disease.”