"Store at room temperature" is the clear instruction found on some vitamin containers. Many others do not mention storage at all, and the refrigerator may seem like a good place to keep your vitamins fresh. Studies have shown that this is not the case, and as it turns out, the kitchen should not be on your list of possible storage places.
Refrigeration and Vitamins
CBS News Medical Correspondent Dr. Jennifer Ashton states that refrigeration can degrade your vitamins. Your vitamins need to be kept dry, Ashton says. In 1981, the New York Times quoted a US Food and Drug Administration chemist, Glen Shue, as saying that opening a refrigerated container of vitamins will introduce condensation, and your vitamins will be exposed to moisture, which will reduce their shelf life. Shue suggested using the refrigerator only for long-term storage. If you buy vitamins in bulk, said Shue, you should take out a specified amount, reseal the container and keep that in the refrigerator. When more is required, you should let the container come to room temperature before opening.
Dr. Lisa Mauer, an associate professor at Purdue University, states that water-soluble dietary supplements may absorb water and dissolve when subjected to high humidity. This process, called deliquescence, will reduce the effectiveness of your vitamins. Every time you open your container, the atmosphere inside changes. The high humidity in your kitchen makes it a less-than-ideal place to store your vitamins. The United States National Library of Medicine Dietary Supplements Database for Bayer Flintstones vitamins has the following statement: "All chewable vitamins should be kept at room temperature with the cap tightly closed."
The "Journal of Agriculture and Food Chemistry" published a study that looked at the stability of vitamin C under conditions where humidity and temperature were varied. It was found that both changes in humidity and temperature affected the stability of the vitamin, and hence the shelf life.
Are Your Vitamins Still Good?
According to Dr. Mauer, deliquescence can cause you to lose the vitamin C in your vitamins within a week. While this may not be the case for all ingredients, to ensure that you are getting the maximum nutritional value when you take your vitamins, you should be on the lookout for signs such as moisture in your vitamin container or brown spots on your pills. These spots are especially common in children's vitamins. While degraded vitamins may not be harmful, Mauer says, they don't have the nutritional value that you are looking for. Let your doctor help you decide if you need to add a supplement to your diet, and keep your vitamins out of bathrooms, kitchens and other high-humidity areas.
- Purdue University News Service: Vitamins Stored in Kitchens Less Effective: West Lafayette, March 2010
- “Journal of Agriculture and Food Chemistry” Temperature and Vitamin C; A. Hiatt et al, Feb. 2010
- CBS News: Best Places to Store Vitamins
- The New York Times: Consumer Saturday Morning: Storing Vitamins