Potential and Dangers of Sorbitol
Lots of foods, drinks, and candies are labeled “sugar-free”, but what does that mean—and what does sugar-free chewing gum have in common with laxatives, IBS, gene therapy, and poison control? Read on to find out more about the uses and side effects of sorbitol.
What is Sorbitol?
Sorbitol is a sugar alcohol. Its chemical structure is very similar to glucose, with an added hydrogen atom. Sorbitol is about 60% as sweet as table sugar, but it doesn’t raise blood glucose like table sugar does [R,R].
Snapshot of Sorbitol
- Low-calorie sweetener
- Will not raise blood sugar in people with diabetes
- Safe, cheap laxative for children and the elderly
- Used to help treat poisoning
- Used in soap and cosmetics
- Digestive upset
- Intolerance is common
- Can trigger IBS flare-ups
- Some drug interactions
- May not be safe for breastfeeding women
Mechanism of Action
The Sorbitol Pathway
Your body breaks down sorbitol with an enzyme called sorbitol dehydrogenase. This enzyme converts sorbitol to fructose, a simple sugar. The liver then converts fructose into glucose, glycogen stores, lactate, and carbon dioxide [R,R].
Glucose is the most common simple sugar and your body’s most important source of energy. Glycogen is a more complex molecule made of many glucose molecules chained together; it stores energy for when glucose isn’t immediately available. Lactate, a form of lactic acid, is cleared by the liver. Carbon dioxide exits the bloodstream in the lungs, where it is breathed out [R,R,R,R,R].
In short, sorbitol is absorbed slowly and eventually converted into usable energy [R].
The Glycemic Index
The glycemic index is a measurement of how much a person’s blood sugar will rise if they eat one gram of a particular carbohydrate. Pure glucose has a glycemic index value of 100; all other carbohydrates are measured as a proportion of this high point. For example, chocolate ice cream has a glycemic index of about 68. This means that if you ate 100 grams of chocolate ice cream, your blood sugar would rise about 68% as much as if you ate 100 grams of pure glucose [R].
If your blood sugar is high for a long period of time, you run the risk of developing type 2 diabetes. Eating foods with a low glycemic index is one way to keep your blood sugar — and your diabetes risk — low [R].
Sorbitol’s glycemic index is extremely low. For example, two common sorbitol-containing bulking agents (substances that add volume to a food and increase feelings of fullness) have glycemic indexes of around 4-7 [R,R].
Uses of Sorbitol
1) Sugar Substitute for Diabetics
Prediabetes and Type 2 Diabetes
Prediabetes and type 2 diabetes are both marked by unusually high blood sugar. Prediabetes often has no symptoms, but the majority of people with this condition eventually silently progress to type 2 diabetes [R].
In fully-fledged type 2 diabetes, the body no longer responds properly to insulin. Normally, insulin signals the tissues to absorb sugar from the bloodstream for energy. When a person develops insulin resistance, as in type 2 diabetes, this pathway doesn’t work properly and the sugar stays in the blood. In the long-run, type 2 diabetes can cause heart disease, kidney disease, blindness, stroke, and nerve damage. In some cases, poor blood flow can lead to the amputation of a foot or leg [R,R,R].
Evidently, it’s very important for a person with diabetes to control their blood sugar, and the best way to so this is through diet. Everyone, but especially people with diabetes, should choose foods that don’t stress their bodies’ responses to sugar or worsen insulin resistance [R].
Sorbitol’s extremely low glycemic index may offer a solution. Foods or drinks with sorbitol won’t spike blood sugar levels like table sugar or glucose [R].
In a study of healthy and diabetic rats, sorbitol reduced the amount of glucose absorbed by the gut and increased glucose uptake into muscles, regardless of whether insulin was present. Rats that consumed both sorbitol and glucose didn’t experience blood sugar increases as much as rats who ate only pure glucose. These results suggest that sorbitol may even help diabetic people control their blood glucose after eating foods containing sugar [R].
Type 1 Diabetes
People with type 1 diabetes, also called insulin-dependent diabetes or juvenile diabetes, may not benefit from sorbitol in the same way as people with type 2 diabetes. In a study of nine patients with type 1 diabetes, blood sugars were measured after a breakfast sweetened with sugar or with sorbitol. The sorbitol sweetener did not help prevent a rise in blood sugars [R].
Constipation, which becomes increasingly common as people age, is a frequent side effect of a variety of medications and supplements for high blood pressure, pain, and anemia. It is painful and frustrating, and it increases the cost of medical care as people need to take laxatives every day to get some relief [R].
Sorbitol is an osmotic laxative, which means that it draws water into the intestine, softening stool and making it easier to pass. Compared with other osmotic laxatives, sorbitol is cheap and easy to find, which makes it a valuable option [R,R].
If you are frequently constipated, a diet high in sorbitol can help.
However, many other natural laxatives may have a more gentle and beneficial effect.
3) Reduced Risk of Cavities
Eating foods with sorbitol instead of sugar may improve dental health. When you eat sugary foods, the bacteria in your mouth ferment some of the sugars and produce acids that increase the rate of tooth decay. By contrast, these same bacteria cannot readily break down sorbitol nor create these harmful acid, which may protect your teeth from cavities [R,R,R].
Unfortunately, this effect may not last forever. Over time, the bacteria living in the mouth can adapt to sorbitol, start using it as a food source, and produce those same harmful acids. Long-term, eating sorbitol won’t benefit your oral health much [R,R].
4) Treatment of Poisoning
Sorbitol is mixed with activated charcoal to prevent poisons and overdosed drugs from being absorbed and doing serious damage to the body. In such cases, activated charcoal binds to a wide variety of toxic compounds, while sorbitol ensures that the charcoal-bound poison passes out of the body quickly in the stool [R,R].
This treatment is also effective in poisoned dogs [R].
Sorbitol Side Effects
1) Breastfeeding Mothers
In rats, sorbitol passed into their milk, and their offspring showed signs of toxicity. These sorbitol-exposed young were smaller than normal and showed signs of liver and bone marrow damage. This effect has not been measured in breastfed babies, but new mothers may want to be careful not to eat too much sorbitol [R].
2) Sorbitol Intolerance
Sorbitol intolerance is very common in children and adults: as many as 32% of otherwise healthy adults develop symptoms of intolerance after consuming 10 grams of sorbitol [R].
Symptoms of sorbitol intolerance mainly affect the digestive system. These include abdominal pain, bloating, nausea, gas, and diarrhea. Many of these symptoms overlap with the symptoms of irritable bowel syndrome, or IBS; in fact, many people with IBS do not absorb sorbitol properly [R,R,R].
If you suspect that you are sorbitol intolerant, ask your doctor to check. Hydrogen breath testing can identify a variety of conditions that cause digestive symptoms, including sorbitol intolerance [R].
3) IBS Flare-ups
Irritable bowel syndrome, or IBS, is a long-term disorder of the digestive system. Its symptoms can be extremely painful and interfere with daily life: abdominal pain and bloating are most common, but people with IBS also report mental and whole-body symptoms like fatigue [R].
Sorbitol, which is not well absorbed in the intestines of people with IBS, can worsen IBS symptoms and lead to flare-ups. More than half of IBS patients had reduced symptoms when poorly absorbed sugars, including sorbitol, were removed from their diets. People with IBS should therefore consider avoiding foods high in sorbitol, especially if they know they are intolerant [R,R].
4) Foods to Avoid on an IBS Diet
The following foods are high in sorbitol and may worsen IBS symptoms [R]:
- Apples, apricots, blackberries, cherries, dates, figs, nectarines, pears, peaches, plums, raisins, and many other dried fruits
- Sugar-free gum and candy
- Foods designed for people with diabetes
- Diet sodas and other sugar-free drinks
Sugar-free and diabetic alternative foods are often sweetened with sorbitol. Check the ingredients if you’re not sure, and keep an eye out for the initials E420. This code is used to identify sorbitol used as a food additive [R,R].
Sorbitol causes diarrhea for the same reason that it helps constipation: sorbitol is an osmotic laxative, which means that it draws water into the intestine and keeps the stool from drying out. A stool with more water is softer and easier to pass. For a constipated person, that’s a good thing. For someone prone to diarrhea, it can be dangerous [R,R,R].
6) Keto Diet Disruption
The ketogenic (or keto) diet uses fats instead of carbohydrates as the main energy source. In order to accomplish this, carbs must be removed almost completely from the diet. Keto diets reduce the symptoms of epilepsy and may also help people with Alzheimer’s disease, Parkinson’s disease, and glaucoma [R,R].
The benefits of a ketogenic diet rely on a state called ketosis; any disruption of nutritional ketosis may interfere with these benefits. While sorbitol does not raise blood sugar much, it may disrupt ketosis. When people with epilepsy are placed on a ketogenic diet to ease their symptoms, they and their doctors must carefully review the ingredients of any medication. Bottles labeled “sugar-free” often still contain sorbitol as a sweetener [R,R].
Avoid sorbitol if you’re on on a keto diet and check the ingredients of “low-carb” or “zero-carb” products to make sure they don’t contain it. It would also be wise to stay away from similar sugar alcohols, such as maltitol and lactitol.
7) Buildup in Diabetes
Sorbitol and fructose increase dramatically in nerve and eye cells in people with diabetes. As a result, nerves become inflamed and a cataract may develop in the eye. Importantly, this buildup of sorbitol does not seem to be related to dietary sorbitol, but to problems in the pathway that breaks down glucose [R,R,R,R].
Is it Safe For Cats and Dogs?
Cats tolerate sorbitol in their diet very well. A preliminary study reported no side effects in female cats receiving up to 280 mg of sorbitol per kilogram of body weight per day [R].
Dogs have been the subjects of multiple studies on poorly-digestible carbohydrates including sorbitol. Sorbitol in combination with activated charcoal may be an effective treatment for canine carprofen (an anti-inflammatory painkiller) overdose [R,R,R].
However, sorbitol is a sugar alcohol. Xylitol, another sugar alcohol, is extremely toxic to dogs: it increases insulin release and causes massive liver damage and death if left untreated. Don’t feed your dog anything that only lists “sugar alcohols” in the ingredients; these sugar alcohols may or may not include xylitol [R,R].
Sorbitol is often given with sodium polystyrene sulfonate (Kayexalate) enema as a treatment for hyperkalemia, a potentially deadly rise in potassium. This combination is associated with extensive damage to the intestines, but researchers do not agree on whether sorbitol, Kayexalate, or an interaction between the two is responsible [R,R,R,R].
The laxative action of sorbitol may also reduce the absorption of other drugs. If you’re taking sorbitol as a laxative, avoid taking your regular medications for 1-2 hours before and after, and consult your doctor.
Lamivudine is an antiretroviral drug used to control HIV-1 infection in children and adults. Sorbitol may decrease lamivudine’s effects, so HIV-positive people taking antiretroviral medication may wish to avoid this sugar alcohol [R].
Limitations and Caveats
Sorbitol is relatively well-studied as a sweetener and a laxative. Its effects on people with an intolerance are likewise well-documented.
However, some of the more recent research into its effects on breastfed infants or on glucose absorption in people with diabetes is still restricted to animal studies. Such research may or may not translate to human studies in the future.
Genetics of Intolerance
There is no current genetic test specifically for sorbitol intolerance. However, the genetic basis for hereditary fructose intolerance, which affects a person’s ability to digest sorbitol, has been well-studied [R,R].
ALDOB Gene Defect
Hereditary fructose intolerance, or HFI, is a metabolic disorder in which the liver, kidney, and intestine don’t produce enough of the enzyme that normally digests fructose. Because sorbitol dehydrogenase converts sorbitol into fructose, people with HFI cannot digest sorbitol properly. In fact, hospital feeding of sorbitol to people with HFI has resulted in deaths [R,R,R].
HFI is caused by a defect in both copies of the ALDOB gene, which codes for the enzyme that digests fructose. When only one copy of this gene is defective, this enzyme is produced normally and HFI does not develop [R,R,R].
An estimated 1 in 20,000 people have HFI worldwide, and roughly 1 in 70 people carry one defective copy of the ALDOB gene [R].
A solution of 70% sorbitol is considered a safe and affordable laxative, especially for the elderly. It is cheaper and has fewer side effects than lactulose, a similar laxative. Sorbitol solution, a thick syrup, is usually taken by mouth [R,R,R].
Relatively pure powdered sorbitol is added to foods to sweeten or moisten them. Sorbitol powder is relatively cheap at around half the cost of maltitol, a similar sugar alcohol. It is usually produced by evaporating the water from sorbitol solution [R,R].
Sorbitol powder begins to have laxative properties at around 50 grams per day [R].
The following foods are naturally high in sorbitol [R]:
- Apples, apricots, blackberries, cherries, dates, figs, nectarines, pears, peaches, plums, raisins, and other dried fruits
Foods with added sorbitol include [R]:
- Sugar-free gum and candy
- Foods designed for people with diabetes
- Diet sodas and other sugar-free drinks
Sorbitol is a humectant, which means that it keeps things moist. This effect prevents baked goods from going stale too quickly. Bakers often add sorbitol to breads, cakes, and other goods for this reason [R,R].
Sorbitol also protects proteins from damage during freezing. During the production of kamaboko and imitation shellfish meats, gels made of cooked pollock fish are washed with mixtures containing sorbitol. This process improves the texture and quality of the gel when it’s frozen and thawed before being made into kamaboko or imitation crab, shrimp, or lobster [R,R,R].
Sorbitol is sometimes added to cooked sausages (like hot dogs and knockwurst) to improve their flavour and quality of cooking because it does not char like sugar or corn syrup [R].
Avoid sorbitol-containing foods and carefully check the product label if you have sorbitol intolerance (look for E420), IBS, diarrhea, or are on a keto diet.
Soap and Cosmetics
Sorbitan fatty acid esters such as sorbitan oleate are compounds made from sorbitol and used to mix together oil- and water-based substances in cosmetics and creams. These are generally considered safe, though some people may have an allergic reaction to one or more sorbitans [R,R].
Sorbitan ester nanoparticles, or SENS, may be used in drug delivery and gene therapy. SENS loaded with cyclosporine, a drug used to treat autoimmune disorders, were absorbed by eye cells at up to double the rate of standard cyclosporine eye drops. Meanwhile, SENS loaded with DNA plasmids efficiently transported new genes into target cells [R,R,R].
Sorbitol vs Xylitol
Sorbitol and xylitol are both sugar alcohols. They are usually made through a chemical reaction that adds a hydrogen atom to glucose (to make sorbitol) or xylose (to make xylitol). These two compounds have similar structures, though xylitol has a chain of five carbon atoms where sorbitol has six [R,R].
Xylitol’s five-carbon structure makes it very difficult to digest for the bacteria that live in your mouth. This means that food sweetened with xylitol is less likely to cause cavities than food sweetened with sugar or even sorbitol [R].
Xylitol is also extremely toxic to dogs, where sorbitol is not. It causes liver damage and a very steep drop in blood sugar. This type of poisoning can be fatal if it isn’t treated, so dog owners who stock low-calorie foods in their pantries should be extra careful to keep xylitol away from their canine companions [R,R].
Sorbitol powder and solution can both be used as laxatives. In powder form, it has laxative effects at around 50 grams per day. In solution, elderly patients take up to 60 mL per day to treat constipation [R,R].
During poisoning treatment with activated charcoal, 70% sorbitol solution is dosed at 4.3 mL per kilogram of body weight every four hours until the poison passes out of the body. An adult man weighing 85kg would therefore be given 365.5 mL every four hours. Children are given a similar volume per weight of 35% solution [R].
Do not attempt to administer these treatments if you are not a medical professional. Please consult your doctor before taking sorbitol as a laxative.
People taking sorbitol as a laxative generally agree that it works, but that its side effects are very uncomfortable.
Some people eating food sweetened with sorbitol experienced many of the same uncomfortable effects. The most common complaints about sorbitol are:
- Smelly gas
- Gurgling stomach
- Painful bowel movements
Sorbitol is added to many foods and drinks to enhance their sweetness or preserve moisture. It has limited benefits for people with diabetes and as a cheap laxative.
However, many people are intolerant to this sugar alcohol. It can cause IBS flare-ups, abdominal pain, bloating, and nausea. If you suffer from gut issues, diarrhea, have sorbitol intolerance, or are breastfeeding, it would be best to avoid it altogether. People on a keto diet should also stay away from sorbitol, as it can disrupt ketosis.
Be sure to check labels on foods, drinks, and medications for sorbitol content (often listed as E420).