Nutrition Diva fan Liz writes:
“What is vegetable glycerin and is it safe? I’ve heard some diabetics use it as a sugar substitute.”

The other day, I was using some vanilla extract in a recipe and noticed that the extract itself had a sweet taste. Liquid extracts often use an alcohol base to preserve the flavor but this particular product (labeled “alcohol-free”) used glycerin instead. I know that vanilla extracts made with alcohol aren’t sweet and I found myself wondering about the nutritional properties of glycerin.   Does it affect the body like sugar? Is it calorie-free?

What is Glycerin?

Glycerin comes from fats (either animal or vegetable) and is a by-product of soap manufacture.   Believe it or not, soap making hasn’t changed much in the 4,000 years since it was first invented. Today, as in ancient Babylon, soap is made by mixing fat with lye. This creates a chemical reaction called saponification. In the end, you end up with soap and glycerin. It turns out that this by-product has a number of interesting properties.

Mix glycerin with nitric acid, of course, and you get nitroglycerine, which can be used to treat chest pain or blow up mountains. Your choice.

On its own, glycerin attracts water like a sponge and this makes it useful as a skin care ingredient. Adding glycerin to a lotion or cosmetic will help your skin hold onto moisture. Mixed into wax and used as a suppository, glycerin’s moisture-attracting properties pulls water from the body into the colon, which stimulates a bowel movement.

Is Glycerin Used as a Sweetener?

Glycerin belongs to a special category of carbohydrates called polyols, which also includes sugar alcohols like sorbitol and erythritol. Like sugar alcohols, which I’ve talked about before, glycerin tastes sweet but it is not metabolized as sugar in the body and doesn’t cause a rise in blood sugar. For that reason, it’s sometimes used as a sweetener in foods marketed to diabetics and low-carb dieters.  Glycerin also has that moisture-attracting property. The same way that adding glycerin to a lotion helps keeps your skin stay plump and moist, adding glycerin to foods helps them stay moist. So glycerin is also widely used in food manufacturing as a preservative.

Is Glycerin Safe?

As with almost any substance, a small number of people have sensitivities or allergies to glycerin and it can be toxic if consumed in sufficient quantities. But as it’s typically used, to keep foods fresh or as a low-glycemic sweetener, glycerin is generally safe. It is not, however, calorie-free. In fact, glycerin contains slightly more calories than sugar—and it’s only about 60% as sweet, so you might need slightly more to get the equivalent sweetness. Also, as with sugar alcohols, consuming a lot of glycerin can produce a laxative effect, which may or may not be desired.

Here’s the bottom line on glycerin as an alternative sweetener: The main advantage is that glycerin does not affect your blood sugar. However, substituting glycerin for sugar will not reduce calories. And consuming it (or foods sweetened with it) in large quantities is not a recipe for good nutrition. I suggest that glycerin—like all forms of sugar and sugar substitutes—be consumed in moderation.

It really keeps coming back to the same thing: Try to build your diet primarily around whole foods—like fresh fruits and vegetables, legumes, eggs, dairy, fish and meat, nuts, and whole grains. Keep processed foods and sweet treats to a reasonable minimum—no matter how they are sweetened!

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