Glycerol

Glycerol, a sugar alcohol that is available under the name glycerin, is a remarkably versatile non-toxic chemical compound. It is used in a wide variety of foods as both a sweetener and a preservative; in sports drinks to treat dehydration; in skin lotions; in toothpaste and mouthwash; and in drugs that treat a wide range of ailments, including constipation, glaucoma, heart arrhythmia, and angina. In addition, it can be used to produce explosives (nitroglycerine), hard enamel lacquer, automobile antifreeze, exterior house paint, and non-irritating bath soap. It is a critical element in the freezing immersion bath used to preserve red blood cells and sperm in donor banks. Glycerol is found in natural fats and oils, and is processed synthetically as a food additive and diet supplement. Natural glycerol has no color and has no odor, but it is glycerol’s gummy stickiness and its heavy sweet taste that most distinguishes it.

Background

Glycerol was among the earliest alcohol compounds to be identified. German research chemist Carl Wilhelm Scheele (1742–1786), one of the most prolific and important (if little known) natural scientists of the late Enlightenment, first isolated glycerol just three years before his death. He described glycerol initially as a sweet fat and recorded in his journals its potential use a sweetener. But its versatility was not recognized until World War I when Allied medical teams used glycerol to treat dehydration in soldiers suffering from diarrhea and heat exhaustion. Desperate field medics also applied the sticky moisturizer to treat minor abrasions, burns, and lacerations.

Before the post-World War II industrial boom in both the United States and Europe created a global demand, glycerol was considered more of a nuisance, produced largely as the byproduct of saponification, that is, the burning of high grade oily animal fat as part of the process for producing commercial-grade body soap. Most of the glycerol was routinely disposed of, the rest used mostly as a food preservative and a skin moisturizer. Glycerol’s natural stickiness meant that water would stick to it making glycerol function like a sponge in retaining moisture in the body; and because glycerol was nearly as sweet as sugar but did not attract and sustain bacterial growth like cane sugar, it provided the sweet taste but virtually eliminated the risk of harmful decay to enamel and teeth.

As the uses for glycerol expanded exponentially during the mid-decades of the twentieth century, demand for glycerol rose. By the early 1990s, on average, almost one million tons of glycerol were being produced, mostly in the United States and western Europe. Ironically, in the twenty-first century, the global market has enjoyed something of a glut of glycerol—it is one of the chief byproducts in the production of biodiesel fuel. As more and more European nations committed to the long-term development of biodiesel fuel as an alternative to imported fossil fuel, the stockpiles of glycerol rose dramatically. Fuel market analysts estimated that as of 2015 the world had nearly seven times the glycerol it could actually use.

Overview

Glycerol is primarily used as a humectant (a moisturizer) in cosmetics and skin lotions; a food preservative used to help maintain the softness and pliability of sugary foods likely to be stored for a period of time (such as cookies or cake icing); as a sweetener and sugar substitute (particularly in sweet liqueurs such as cordials, crème de menthe, brandies, and schnapps); and as a lubricant to maintain the viscosity of health care products with long shelf lives, such as mouthwash, toothpaste, cough syrup, and liquid laxatives.

Glycerol is used in two newer applications, both part of pop culture fads that have, in turn, sparked some controversy amid health professionals and nutritionists: fast-acting sports drinks and so-called e-cigarettes. The Food and Drug Administration classifies glycerol as a carbohydrate, that is an organic nutrient compound able to break down into sugar, thus providing the body with a quick spike in energy. Given its ability to also hold onto water molecules, glycerol can act as well as a hydrator for the body, storing water during extreme high-energy activity or, when taken during such activity, providing a high-energy buzz by temporarily flooding the body’s system with reservoirs of water. Savvy marketing promotes glycerol as an endurance enhancer, able to sustain longer periods of high-energy activity among serious athletes. In addition, glycerol has gained a reputation as a quick-fix weight-loss supplement, particularly among those extreme dieters who seek to lose weight rapidly, often by purging or by encouraging laxation. Because research into hard data to explore the implications of using glycerol as part of a high-intensity physical activity regimen is ongoing, nutritionists and athletic coaches caution against using glycerol as some kind of panacea.

E-cigarettes are widely marketed as less toxic both to smokers and to those around them because smokers of e-cigarettes inhale flavored aerosol rather than burnt tobacco. Since being introduced in 2004, use, particularly among young people, has skyrocketed. They have become both a fashion statement and a status symbol and unlike cigarettes, e-cigarettes do not carry age requirements and can be used in many areas where smoking is prohibited. Vegetable glycerol is the preferred additive to the vaporization process as it gives the vapor a pleasant sweet taste and gives the smoker a momentary sugary high. That high particularly appeals to the targeted demographics of young adults. But little hard research is available yet whether e-cigarettes are as safe as their manufacturers indicate. As of 2016, there was some concern that heating glycerol as part of the liquid in e-cigarettes could produce toxic by-products such as formaldehyde, which is a carcinogen; research was ongoing into how much heat would need to be applied to produce this effect and to what extent.

Bibliography

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Ross, John. "E-Cigarettes: Good News, Bad News." Harvard Health Publishing, 25 July 2016, www.health.harvard.edu/blog/electronic-cigarettes-good-news-bad-news-2016072510010. Accessed 26 Feb. 2018.

Wingo, Jonathan E., et al. "Influence of a Pre-Exercise Glycerol Hydration Beverage on Performance and Physiological Function during Mountain-Bike Races in the Heat." Journal of Athletic Training, vol. 39, no. 2, 2004, pp. 169–75.