Vitamin pills degrade "within a week of opening"Storing pills in bathrooms and kitchens a bad idea
Vitamin pills and other dietary supplements are a multi-million pound industry, with many of us taking them on a daily basis. We even give them to our children hoping that the extra vitamin intake will make them healthier.
But a new study has found that the nutritional value of many of these pills can rapidly fade if they are stored in humid conditions - such as those in our kitchens and bathrooms.
Many vitamins are made of crystals and are prone to a process known as deliquescence, i.e. they can dissolve in water derived from humid air. This is also known as "caking" where crystalline substances such as salt and sugar clump together in lumps.
Leader of the study, Lisa Mauer from Purdue University, commented: "You might see salt or sugar start to cake in the summer, start to form clumps, and that's a sign of deliquescence.
"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."
Once a bottle of vitamin pills is opened, air will enter. If the air is of high humidity then the chemicals in the vitamins can become damaged.
As luck would have it, people often store vitamin pills in bathrooms and kitchens, two of the most humid rooms in the home. Day-to-day activities such as washing, showering, cooking and using dishwashers and washing machines all increase the short term humidity of the air substantially, sometimes by as much as 98%.
If the humidity in the air is high enough, the vitamins in pills may dissolve completely. This can occur at humidity levels as low as 30% for some combinations of ingredients.
"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 continued.
"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."
Once the humidity returns to normal the chemicals will re-solidify, but by this time the value of the vitamin will be destroyed.
"Any chemical changes or degradation that have occurred before resolidification don't reverse. You don't regain a vitamin C content after the product resolidifies or is moved to a lower humidity," she said. "The chemical changes we've observed are not reversible."
Mauer pointed out that although the degraded vitamins are not dangerous, they are, at this point no better than sweets, so there would be no point giving them to children.
Consumers could notice liquid in vitamin containers as evidence of degredation, said Mauer. However, another sign of nutrient degradation is brown spots, especially on children's vitamins.
Mauer suggested discarding any dietary supplement that is showing signs of moisture uptake or browning. Pills should be stored in dry conditions to maintain their nutritional value as long as possible.
This article was published on Thu 4 March 2010
Image © Purdue Agricultural Communication photo / (Tom Campbell)
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