By Margarita Nahapetyan
Kitchens and bathrooms turn out to be wrong places to store our vitamins. A new study came to the conclusion that high humidity and temperatures, such as those from stoves, dishwashers and showers, can hasten the degrading of vitamin C potency and shorten the shelf life of health supplements.
Scientists at a Purdue University found that the most common types of vitamin C used in vitamin supplements and other fortified products are susceptible to a process called deliquescence, during which humidity causes a a water-soluble substance melt or become liquid. This, in turn, reduces the quality and shelf life of the vitamins, even if the bottle caps are on tight, and means that we are not getting all the nutrition we are supposed to.
The new research studied the breakdown of the two most common forms of vitamin C, sodium ascorbate and ascorbic acid, under different temperatures and humidities in the lab facility. Complex lab methods were used in order to examine both forms of the Vitamin C, which have different deliquescence points. This included storing the vitamin C in a chamber above different saturated salt solutions, exposing it to different humidity conditions and to temperatures from 4 degrees Celsius to 40 degrees Celsius.
After the different exposures, the scientists examined the breakdown of vitamin C using colourimetry, a special form of photometric analysis that indicates the concentration of vitamin C in a supplement. The amount of moisture that had been absorbed by the vitamin was measured using a technique known as gravimetric sorption analysis. The two forms of vitamin C were analyzed over an extended period of 8 weeks and assessed on a regular basis to see at which point they achieved 50 per cent degradation - their half-life. The results revealed that both humidity and temperature greatly affected the stability of vitamin C, but humidity had the most significant effect.
Although the effect that was observed in this lab study may also happen in supplements and vitamins used at home, it is not clear yet if the different forms of vitamin C will degrade at the same rate. In general, supplements contain many other nutrients, minerals and ingredients, some of which play a role of preservatives. For instance, silica, which absorbs water and moist, is often included in many supplements.
So how do we know if our vitamins are degrading or not? The experts say that the first sign of nutrient degradation is usually the appearance of brown spots, especially on children's vitamins. They strongly recommend discarding any vitamin supplement that started showing signs of color changing or moisture in the container.
Vitamin C is one of the most popular and widespread nutrient supplements, but it is also quickly degraded by exposure to heat, humidity, light and air. As such, vitamin C is commonly monitored when determining shelf life. The experts say that a new study looking at the degradation of vitamin C though its exposure to heat and humidity would be of a great importance. In particular, it would help to better understand the process of deliquescence.
The research was supported by grants from the US Department of Agriculture (USDA).