Vegetable glycerin is a common ingredient in many dog foods and treats. Read on to find out what you need to know about this ingredient … what’s it used for and whether it’s truly natural. And is vegetable glycerin safe for dogs or should you avoid it?
What is Glycerin?
Glycerin, also known as glycerol, is sugar alcohol. Its a syrupy liquid compound made from animal fats, some plant oils, or petroleum. It has no color or odor and is sweet tasting. It’s a by-product of soap and biofuels production and the plentiful supply has created pressure to find uses for it in other ways …including in animal feeds.
According to the FDA, glycerol is non-toxic and therefor safe to use as an additive in many drugs, cosmetics, and foods. However, studies on the safety of glycerin for dogs are rare.
What is Vegetable Glycerin?
Vegetable glycerin is glycerin made from plant oils, usually coconut, soybean, or palm oils. You’ll see it as an ingredient in some moist pet foods and treats for dogs.
Uses of Glycerin
Glycerin is commonly used in drugs for its antimicrobial properties. It’s also an ingredient in many cosmetics, including hair care products, soaps, and toothpaste. You may see it as an ingredient in dog shampoos.
It’s used in many foods as a solvent for flavor and food coloring, as well as a sweetener in low-fat processed foods.
Herbal extracts can be made with glycerin (called glycerites) instead of alcohol (called tinctures).
Benefits of Glycerin
Glycerin is a humectant, which means it attracts moisture. That’s why it’s used in human dry skin products – because it helps trap moisture in the skin. This also makes it useful in pet foods because it helps give food a moist, chewy texture while preventing it from drying out or getting moldy.
Glycerin has some medical uses as well, including as a laxative or to help relieve pressure due to glaucoma and brain swelling (1).
It has benefits for food processing and preservation, including thickening liqueurs, preserving moisture in dried fruits and vegetables, and as a sweetener.
Side Effects of Glycerin
Glycerin is a sugar alcohol that cannot be fully absorbed by the body. Excessive amounts of glycerin may cause cramping, irritated bowels, diarrhea, and gas. However, there haven’t been any studies looking at the effects of glycerin in dogs.
Is Vegetable Glycerin Safe for Dogs?
Vegetable glycerin is in a number of different dog products.
Shampoos And Skin Care Products
Vegetable glycerin in safe for dogs in shampoos and skin care products. It holds moisture in, so can soften and soothe your dog’s skin. Look for skin products with organic ingredients, including vegetable glycerin.
As mentioned earlier, some herbal medicines are extracted using vegetable glycerin instead of alcohol.
Glycerites are safe for dogs. Your dog will only get a few drops per dose so it’s a small amount of glycerin. And, because they taste sweet, they can be more palatable for dogs than alcohol tinctures. Herbalists Gregory Tilford and Mary Wulff say that glycerites are metabolized more like triglycerides than sugar, so they can be better than tinctures for dogs with diabetes or alcohol sensitivity.
However, glycerites usually require higher dosages than alcohol tinctures because glycerin doesn’t extract as much of the herb’s constituents. They don’t keep as long as alcohol tinctures but can last up to 2 years if refrigerated.
Canine herbalist Rita Hogan also warns that you must verify the source of vegetable glycerin used in the products you buy. Some companies use poor quality, industrial vegetable glycerin from biodiesel production. This is also a reason to avoid glycerin made from corn, which is used to make biodiesel … especially non-organic or genetically modified corn.
So If the label only states “vegetable glycerin,” call the company to find out the source. Vegetable glycerins made from organic soybean, coconut or palm oil are the usual choices. If you’re using a lot of glycerin products, don’t overdo coconut oil based products, because it can be bad for your dog’s gut health. The environmental impacts of using palm oil are also a concern. This is especially true in countries like Malaysia and Indonesia where palm oil deforestation causes loss of animal habitat as well as increased greenhouse gases.
Caution: In people, vegetable glycerin can cause headaches, nausea, diarrhea or other digestive problems. So if you notice your dog doesn’t feel well after you’ve given herbal glycerin extracts, it’s likely the glycerin that’s the problem and you’ll want to stop using glycerites. Rita Hogan also says some sensitive dogs may drool excessively after dosing with glycerites.
Vegetable Glycerin In Dog Food And Treats
There’s been little research specifically into the safety of glycerin for dogs. That means there’s no proof that it’s unsafe … or that it’s safe.
Dutch pet food researcher Anton C Beynen said in a 2019 paper (2) that “It is noteworthy that the purity of glycerol preparations in the marketplace is variable.”
He also observed, “Practical feeding of glycerol-containing petfoods has apparently not yielded observations that point to negative effects on canine and feline health. However, for long-term, practical intake levels of purified and crude glycerol, the current research data cannot exclude health risks.”
There’s a lack of long-term data. Beynen suggests that glycerol in semi-moist pet foods may affect the ability of puppies and cats to break down food into energy So it would probably be a bad idea to feed your dog a food with this ingredient over the long term.
Beynen also cited a 1933 study by Johnson et al, that showed high glycerol intake (35%) did not affect growth of puppies during age 5 to 35 weeks, or cause any other noticeable adverse effects. But this was a very small study, with only 3 dogs eating glycerol in their food.
One concern is that the glycerol-fed dogs drank more water and urinated 5 times more than others in the study. This isn’t surprising because a separate study showed oral glycerol has diuretic activity in dogs. Beynen comments, “The excessive thirst in the glycerol-fed dogs would be understandable if their kidneys excreted glycerol, thereby drawing water into the urine by osmosis.” Again, the effects are unclear and this is another reason for caution with this ingredient … especially if there’s a risk of stressing your dog’s kidneys.
Always Verify The Source Of Vegetable Glycerin
As before, the safety of vegetable glycerin as a food or treat ingredient depends on which plant oil the glycerin comes from. Production of biofuels leads to residual methanol and sodium in the glycerin co-product stream. In the US, the FDA designates most glycerin as generally recognized as safe (GRAS), but this does not apply to crude glycerin from biodiesel production.
So again, Rita Hogan stresses it’s important to find out the oil source of vegetable glycerin before you give your dog food or treats you buy with this ingredient.
Glycerin In Chinese Jerky Treats
After many years, there’s still controversy surrounding glycerin in Chinese jerky and other recalled pet foods in the past.Though there has not been a causal link identified between glycerin and pet illness (and even death), there have been reports about pet foods imported into the US having harmful glycerin substitutes used in place of glycerin.
Other Reasons For Caution With Glycerin
Animal nutritionist and natural pet treat manufacturer Anthony Bennie wrote a white paper about vegetable glycerin in dog treats.
“Vegetable Glycerin,” as designated on pet treat ingredient lists, is most often a by-product of saponification, the manufacturing of soaps and detergents from vegetable oils.”
This means vegetable glycerin is a chemically altered ingredient that isn’t truly natural. And there’s another problem: glycerin may be a much bigger percentage of the end product than you think.
Even though vegetable glycerin may be on the ingredient list as one of the minor ingredients, the label can be deceptive. That’s because glycerin doesn’t get reduced during cooking. So a moist treat that that starts out with glycerin as 10% to 15% of the formula, ends up having 20% to 30% glycerin content when other ingredients lose moisture and shrink during cooking. That’s a lot of glycerin.
So … because there’s no research into the health effects of your dog eating it regularly or long term, it’s best to err on the side of caution. Don’t feed a lot of treats and foods that contain vegetable glycerin.
It’s best to avoid everyday dog foods with vegetable glycerin, and minimize treats with this ingredient. And if you do feed treats with glycerin, make sure the ingredient list specifies vegetable glycerin. Otherwise, it’s likely to be a petrochemical product. And then follow Rita Hogan’s advice: go a step further, and find out what’s in the vegetable glycerin. Look for vegetable glycerin made with organic plant oils.
What is the Healthiest Treat for Dogs?
The best way to avoid dangerous artificial ingredients is to stay away from processed foods altogether and feed your dog only natural treats.
You can dehydrate meats and organs yourself in a food dehydrator or a very low oven. Or, if you buy jerky treats for dogs, make sure they have no added ingredients (like glycerin, dyes or flavorings). Fruits and vegetables can be a great, healthy snack. Many dogs love apples, green beans, broccoli, and carrots. Organic fruits and veggies don’t contain harmful preservatives and they have many beneficial nutrients, like antioxidants, vitamins, minerals, and prebiotics that contribute to a healthy digestive and immune system.
Even small items like treats should be healthy for your dog. If you’re feeding your dog a wholesome raw diet, and avoiding processed dog treats, then you don’t need to worry about vegetable glycerin.
1. Padmawar, A.R. and Bhadoriya, U. Glycol and glycerin: pivotal role in herbal industry as solvent/co-solvent. World Journal of Pharmaceutical and Medical Research. 2018;4(5):153-155.
2. Beynen, AC. Glycerol in semi-moist pet foods. Petfood Magazine 2019; Nr 1: 24-25