Re: what happen inside the expired vitamin supplement?

Vitamins can become oxidized and lose their potency. This is very dependant 
on the temperature of storage, amount of direct light exposure, and 
moisture present.Unless dirty fingers or utensils have been used for the 
vitamins, bacteria/viral contamination would be rare. Vitamins will have 
expiration dates that is an approximate time,after which, some or most of 
the vitamins will start to lose their potency (of original concentration 
listed on the bottle). However, if the bottle is tightly closed and kept in 
a cool, dark place, a few months after the expiration date may have very 
little effect. It is very difficult to predict if 6 months, 8 months, or 2 
years after the expiration date has caused degradation of each vitamin 
since there are so many variable factors to be considered. You could ask 
your local pharmacist, or call the 800 company number (if present on the 
bottle) for additional information. The company usually will stand by their 
expiration date, after which their product potency cannot be guaranteed. To 
be absolutely sure that you are getting the amount of vitamin 
concentrations described on the bottle, one would not use after the 
expiration date listed.