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Take Your Vitamins Out of the Kitchen, Bathroom


The kitchen and bathroom are not recommended places to store your vitamins, according to a Purdue University study. The high humidity in these environments could cause your supplements to lose some or all of their value and shorten their shelf life.

You may have experienced this in your kitchen: salt, sugar, or powdered drink mixes that have clumped or caked together because they were exposed to humidity. Now imagine the same thing happening to your vitamin and other nutritional supplements, only you may not see it happening. Even if you put the bottle tops on tight, your vitamins and other supplements may be exposed to damaging humidity.

According to Lisa Mauer, an associate professor of food science at Purdue University, crystalline substances, such as vitamin C, some B vitamins, and other dietary supplements, can succumb to a process called deliquescence, in which humidity causes water-soluble solids to dissolve. Vitamin C and B vitamins are water soluble, thus they can be damaged when exposed to humid environments.

While the chemical changes that cause salt and sugar to clump are a nuisance, deliquescence can make vitamins and other supplements much less viable or even completely useless, depending on the conditions and formulations of the supplements. According to Mauer, “Within a very short time—in a week—you can get complete loss of vitamin C in some products that have deliquesced.”

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Mauer tested vitamins and other supplements using a gravimetric moisture sorption balance to identify the amount of humidity at which different substances in supplements would deliquesce. Fructose reacted at 62 percent, ascorbic acid (vitamin C) at 98 percent, and sodium ascorbate (another form of vitamin C) at 86 percent humidity. At high humidities, some samples dissolved completely.

Every time you remove a lid from a supplement bottle, the contents are exposed to varying amounts of humidity and moisture. Once humidity or temperature go back down, the product can solidify, but any nutritional value that the supplement has lost because of the exposure is gone forever.

Generally, vitamins and other supplements should be stored in a dry, dark place away from humidity and temperature changes. Thus supplements should not be placed in sunlight or in the refrigerator unless the label specifically says they should be refrigerated. Some people find that keeping supplements in their bedroom is a safe alternative.

Vitamins and other supplements should not be stored in a kitchen or bathroom. If supplements do become damaged, Mauer recommends consumers dispose of any containers that have moisture or supplements that show signs of deliquescence, such as brown spots, flaking, pitting, or other physical signs of damage.

Purdue University news release, Mar. 2, 2010