Glycerin is an ingredient widely used in food, personal care, and medicinal products. How to determine its safety or toxicity based on type and manufacturing method.
Glycerin is one of the most common ingredients in the world. Industry loves this sticky, thick liquid because it is colorless, odorless, and above all …. SWEET.
Hence its wide and varied use in processed foods, personal care products, and medicines.
In fact, there is almost no industry where you won’t find it – particularly the plant-based version known as vegetable glycerin or glycerine as some people spell it.
It’s even one of the main ingredients in vaping liquid.
What is Glycerin?
According to the PubChem database, glycerin “is a trihydroxy sugar alcohol that is an intermediate in carbohydrate and lipid metabolism. (1)
Wow, what a mouthful, eh? Let’s unpack this.
So, first and foremost, glycerin is a sugar alcohol.
Well, glycerin goes by another name which fits right in semantically speaking – glycerol.
Like all sugar alcohols, glycerol is sweet without containing sugar. This is why it was named “glyc,” which is the Greek root for sweet.
Chemist Carl Scheele discovered glycerol in 1779, and not long after, scientists learned of its indispensable role in human metabolism.
What makes this chemical so special? It is a naturally occurring molecule in all plant and animal fats! They owe their structure and integrity to glycerides, which form a glycerol-based backbone of sorts.
So glycerin/glycerol is 100% natural in its most primal form.
While industry can obtain glycerol from literally anywhere, companies prefer to use vegetable glycerin almost exclusively. More on this below.
You are probably most intimately familiar with glycerol’s role in your health per your triglyceride levels. Triglycerides are actually esters of glycerol. (2)
If you haven’t noticed already, glycerol from plants, aka vegetable glycerin, is an ingredient in a LOT of stuff!
From industrial uses to body care, medicines, and even low-carb recipes and foods, you will find glycerin literally everywhere if you start to look for it.
This is because glycerin is really good at the things it does. It plays an important role in nearly every industry on the planet. (3)
Glycerin’s 10 most important superpowers are as follows.
Top 10 Benefits of Vegetable Glycerin
When it comes to using glycerin in manufacturing, these are the top ten benefits it imparts to the final product.
- Glycerin is an excellent emulsifier. This means that it helps join fats and other liquids together so they don’t separate.
- Its second important feature is as a solvent, meaning it helps one compound dissolve evenly into another. This is useful for the preparation of tinctures and the distribution of food coloring.
- Due to its preservative qualities, companies use glycerine as a stabilizer and an auxiliary solvent in conjunction with water or alcohol.
- The pharmaceutical industry uses glycerol to extract and prevent inert materials from precipitating (coming out of solution to form a solid) when in storage. In foods, this property works well as a carrier for extracts and flavoring agents.
- When dried, glycerin has a plastic quality that is beneficial to coat tablets, beads, and granules.
- Dried glycerol serves as an excellent reducing agent to decrease the particle size of a drug powder.
- Glycerin’s humectant and emollient properties are beneficial for drawing moisture out of one substance into another. This makes it useful as a pharmaceutical ingredient to prevent the drying out of preparations, particularly ointments and creams.
- In the food industry, glycerol is an important moistening and sweetening agent for baked goods.
- Food companies add it to candies and icings to prevent crystallization.
- Glycerol adds smoothness and thickness to any product that contains it. For this reason, glycerin is an ubiquitous ingredient in toothpaste. This surprisingly includes many natural and organic brands.
Glycerin is an important ingredient in homemade products and foods as well.
Because it is a humectant (helps preserve and slow the loss of moisture), glycerol is indispensable in DIY skin care products including soaps, moisturizers, lotions, masks, and more!
Since it is sweet and also a solvent, it is often used to make herbal tinctures. Alcohol tinctures are not always well-liked by kids and some parents shy away from giving alcohol of any kind to small kids, so glycerin-based tinctures are popular for two reasons. It has a naturally sweet taste without any sugar or alcohol.
Since glycerin contains no calories or sugars, it is also sometimes used in sugar-free, low-carb, and other foods made at home for those on special diets.
Glycerin has many well-researched, beneficial uses, especially for skin conditions. It is often part of treatments for dermatitis, and other skin issues. It also helps promote wound healing, so it is sometimes used in salves and other skin balms. (4, 5)
Note that glycerol draws moisture from wherever it can get it.
In humid environments, it will do it from the air, but in dry environments, when applied to the skin it will draw moisture up from the deeper layers.
This can dry out the dermis and is one reason it is rarely used alone.
While glycerol-containing skin products are not dangerous and may even be beneficial, glycerin toothpaste and other oral care products should be avoided.
This includes organic brands of toothpaste, mouthwash, and dental floss.
The problem occurs due to an inherent stickiness that encourages small amounts to remain on the teeth after cleaning.
This inhibits the mineral-rich saliva from contacting the entire surface of the teeth which can impede remineralization.
In short, toothpaste containing glycerin/glycerol may encourage the formation of cavities! This goes for homemade toothpaste too!
How is Vegetable Glycerin Made?
There are a number of ways to make glycerin. This is where the rubber meets the road with regard to its safety or toxicity.
Since it naturally occurs in all plant and animal fats, creating pure glycerin simply involves separating it out from the rest of the fats and compounds.
So how does industy do that? And can you do that at home yourself?
As alluded to above, the industry almost exclusively uses vegetable glycerin. This is because the process is most cost-effective when using plants.
Plant-based glycerin is mostly a by-product of soap manufacturing. This process involves heating vegetable oil with a strong alkali such as lye (sodium hydroxide).
After that, some straining, separating, and concentrating creates a pure end product. There are several excellent online tutorials if you are so inclined to try it at home. (6,7)
Another way manufacturers make it is by heating coconut, soy, or palm oil under pressure with water so that the glycerin splits off into the water. Subsequent distillation then isolates the glycerin. (8)
So, we see that glycerin and mankind have worked together for a long time. As long as soap-making has been around, so has glycerin! It is also a by-product of candle making and the creation of biodiesel.
Unfortunately, natural processes are not the only way to make glycerin!
Synthetic glycerin is very commonly used in industry nowadays.
It is a complex process that may begin with substances such as allyl chloride, acrolein, propylene oxide, polyalcohols, fats, or epichlorohydrin. Some of these chemicals are quite dangerous.
Allyl chloride, for example, causes toxic polyneuropathy (multiple nerve damage) with prolonged exposure.
One glycerin-synthesizing method involves the oxidation of allyl chloride with hypochlorite to produce dichlorohydrin, which converts to epichlorohydrin. The process subsequently hydrolyzes the epichlorohydrin to yield a glycerin solution.
Distillation then separates the water and glycerin with further refining to remove color and odor.
Another way to synthetically create glycerol is to oxygenate propene to acrolein, reduce it to yield allyl alcohol, and then epoxidate it with hydrogen peroxide. That creates glycidol, which industry hydrolyzes to produce glycerin. (9)
Sound complicated? It is!
It is primarily from these artificial glycerols that the potential for toxic residues and health dangers occurs.
Finding the Best Quality
Glycerin is one of those substances that can be safe when of high quality and unsafe when of low quality.
The high-quality glycerin is the only kind you want to ever ingest or put on your skin (but, never your teeth due to the stickiness).
First and foremost, if you purchase glycerin, make sure it is FOOD grade or, even better, PHARMACEUTICAL grade (even higher/purer than food grade).
Second, go for either certified organic brands or those that utilize cleaner sources, such as palm or coconut oil.
Many companies selling glycerin, even relatively good companies that I contacted, are selling unsafe glycerol from GMO soy or other such industrialized crops!
Also note, some sources of glycerol are synthetic and the process used to make it involves all sorts of not-so-natural-looking chemicals and processes as described above.
Stay away from artificially synthesized glycerol with the potential for toxic residues.
Have you used glycerin in cooking or making homemade body care products?
If so, have you found a good quality source you can share?
(1) PubChem Database
(2, 3) The Future of Glycerol
(4) Double-Blind Study on the Effects of Glycerin and Urea on dry, eczematous skin
(5) Glycerin-Based Hydrogel for Infection Control
(6) Old School Beauty Basics: How to Make Glycerin
(7) How to Make Glycerin from Vegetable Oil
(8, 9) Naturally Derived Vegetable Glycerin