Lisa Mauer, Associate Professor of Food Science at Purdue University, Indiana, whose research was published in the Journal of Agricultural and Food Chemistry, suggested that the Vitamin supplements stored in a kitchen cupboard could become useless in over one week because of the humid environment.

Even the products kept in bottles with lids might not stop the pills from degrading.

Signs of supplements expiring are indicated by the presence of liquid in the containers or brown spots on capsules.

Crystalline substances including vitamin C, some forms of vitamin B and other dietary supplements were found prone to an irreversible process called deliquescence, which causes chemical instabilities in products.

Professor Mauer said, "If ingredients dissolve they will decrease the quality and shelf life of the product and decrease the nutrient delivery".

Essential nutrients get degraded by simply dissolving into the air in the presence of high level of humidity found in kitchens and the bathrooms, as the change in the atmosphere adds a little bit of humidity and moisture each time the bottle is opened or closed.

Keeping those supplements away from warm, humid environments help restore their effectiveness.