Glycerol

Glycerol, a sugar alcohol that is available in commercial and pharmaceutical forms 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 or 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 as 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 reaction of oily animal fat or oils with alkali as part of the process for producing commercial-grade body soap. Most of the glycerol was routinely disposed of, and the rest was 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 even by 2015 the world had nearly seven times the glycerol it could actually use. Into the mid-2020s, the demand for glycerol increased across various industries, such as personal care, pharmaceuticals, and biofuels, but the supply still exceeds demand in some regions.

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 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 or vaping. The Food and Drug Administration classifies glycerol as a carbohydrate (specifically, sugar alcohols or polyols) and are generally recognized as safe, 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 also act as a hydrator for the body, storing water during extreme high-energy activity or, when taken during such activity, providing a hyper-hydrated feeling by flooding the body’s system with reservoirs of water, also drawing water into the muscles and increasing their volume. 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. In addition, high doses could cause gastrointestinal distress.

E-cigarettes and vapes are widely marketed as less toxic both to smokers and to those around them because smokers 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, vapes 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. While once thought of as a safe alternative to smoking, by the mid-2020s, several studies had exposed the health risks of vaping. Heating glycerol and propylene glycol in vapes can produce toxic by-products, including formaldehyde, acrolein, and acetaldehyde. Vaping can lead to health conditions, such as chronic asthma and chronic obstructive pulmonary disease.

Bibliography

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