High humidity present in bathrooms and kitchens could be degrading the vitamins and health supplements stored in those rooms, even if the lids are on tight, a Purdue University study shows.
Lisa Mauer, an associate professor of food science, said that crystalline substances - including vitamin C, some vitamin B forms and other dietary supplements - are prone to a process called deliquescence, in which humidity causes a water-soluble solid to dissolve. Keeping those supplements away from warm, humid environments can help ensure their effectiveness.
"You might see salt or sugar start to cake in the summer, start to form clumps, and that's a sign of deliquescence," said Mauer, whose findings were published in the early online version of the Journal of Agricultural and Food Chemistry. "You can also get chemical instabilities, which are a little more problematic if you're consuming a dietary supplement with vitamin C for that vitamin C content."
Kitchen salt, sugar and powdered drink mixes commonly cake, Mauer said, making their measurement more difficult but not rendering them useless. Chemical changes become more than a nuisance in vitamins and dietary supplements, however.
"If you get some moisture present or ingredients dissolve, they'll decrease the quality and shelf life of the product and decrease the nutrient delivery," Mauer said. "You can get complete loss of the ingredients. It depends on the conditions. It depends on the formulations. Within a very short time - in a week - you can get complete loss of vitamin C in some products that have deliquesced."
Bathrooms and kitchens can increase the detrimental effects because of spikes in humidity in those rooms. And Mauer said storing vitamins or supplements in containers with lids doesn't always help.
"Opening and closing a package will change the atmosphere in it. If you open and close a package in a bathroom, you add a little bit of humidity and moisture each time," Mauer said. "The humidity in your kitchen or bathroom can cycle up quite high, depending on how long of a shower you take, for example, and can get higher than 98 percent."
Mauer used a gravimetric moisture sorption balance to determine the humidities at which substances would deliquesce. The samples spiked in weight at the deliquescence point because moisture was being adsorbed, meaning humidity was condensing on the solid and then the solid dissolved.