Xylitol is a naturally-occurring sugar alcohol found in plant material. Most commercial xylitol is extracted from the bark of birch trees and used as a sugar substitute in things like sugar-free chewing gum and (more recently) in sugar-free keto and low-carb treats.
Xylitol and other sugar alcohols taste like sucrose (table sugar) but don’t count as net carbs because they don’t spike your blood sugar levels.
But what does the science say about the benefits and risks of a sugar substitute like this? Are xylitol-containing products really keto friendly? I.e., do they really keep your blood sugar levels stable, despite the sweet taste?
Read on to find out about the benefits and drawbacks of xylitol for your keto lifestyle, and the best ways to satisfy your occasional sweet tooth on keto.
Xylitol is a sugar substitute used mainly as a sweetener in manufactured products like chewing gum, supplements, toothpaste, other oral care products, and pharmaceuticals. It occurs naturally in low amounts in some fruits and vegetables and during normal human metabolism.
Sugar alcohols are a type of polyol. Other common sugar alcohols include sorbitol and erythritol. They’re manufactured by adding extra hydrogen to existing sugar molecules.
While xylitol is as sweet as sucrose (table sugar), its glycemic index is 7 (compared to 100 for glucose and 65 for sucrose)[*]. It has 60% fewer calories than real sugar.
Some people notice a “cooling” flavor or mouthfeel when they use xylitol and other sugar alcohols in recipes
#1: Barely Spikes Blood Glucose and Insulin
When you consume xylitol, it has a minimal effect on your blood sugar and insulin levels. Approximately 10-20% of xylitol is excreted in your urine instead of being digested[*].
Scientists have reported that xylitol has a low glycemic index — it only raises your blood sugar levels 7% compared to glucose, which is inconsequential at typical dosage[*]. Humans can metabolize it without releasing insulin[*].
#2: May Improve Oral Health
Unlike real sugar, sugar alcohols don’t contribute to dental caries (cavities)[*].
While it’s clear that xylitol and other sugar alcohols can reduce tooth decay, researchers aren’t entirely sure how.
There is some evidence that they change the composition of mouth bacteria. Some research suggests that xylitol is responsible for a decrease in plaque formation because it inhibits the growth of Streptococcus mutans and Streptococcus sobrinus bacteria[*].
#3: May Reduce Intestinal Glucose Absorption and Improve Muscle Glucose Uptake
According to a study of the effects of xylitol on rats, it can reduce the absorption of carbs by inhibiting digestive enzymes[*]. The same scientists also found that it improves muscle glucose uptake[*].
If these health effects translate to humans — which is unknown — xylitol might reduce the adverse impact of high-carb meals and offset insulin resistance in muscle cells.
That means that people with insulin resistance or those predisposed to diabetes may benefit from replacing sugar with an alternative like this one.
#4: Might Accelerate Ketosis
A study of 72 surgical patients undergoing gastric resectioning or gallbladder removal found that xylitol increased ketone levels and led to ketosis, even when combined with carbohydrates[*].
While these results don’t shed light on the effects of xylitol on the average person’s metabolism, they do suggest there could be a benefit to consuming it on the keto diet.
The good news is you can quickly learn for yourself by testing your ketone levels after xylitol consumption.
#1: May Lead to Difficulty Losing Weight
A study published in 2017 in the International Journal of Obesity found that obese individuals participating in a year-long weight loss program were less likely to lose weight if they had higher xylitol levels to begin with[*].
However, correlation doesn’t equal causation. The researchers were unable to determine whether xylitol in the participants’ bloodstream was from their diet or produced by their own metabolism.
Even if the xylitol came from their diet, a randomized controlled trial would be required to determine whether it was responsible for reduced weight loss. Therefore, this study alone doesn’t prove that consuming xylitol makes you less likely to lose weight.
That said, if you are having trouble losing fat, you might want to consider cutting out xylitol along with conventional sources of carbohydrates.
#2: It Can Cause Diarrhea
All sugar alcohols can cause diarrhea in sufficient quantities, and xylitol isn’t the worst culprit.
For most people, the maximum “safe” dose of xylitol that doesn’t cause diarrhea is approximately 0.35 grams per kilogram of body weight (that’s about 24 grams or ~2 tablespoons for a 150-pound individual)[*].
Unfortunately, this guideline isn’t accurate for everyone[*]. Some people are sensitive to xylitol, so your results may differ.
#3: It’s Usually Made from Corn
Most sugar alcohols, including xylitol, come from by-products of forestry and agriculture. Corn and corn cobs are one of the most common sources from which xylitol is derived.
Unfortunately, farmers spray virtually all non-organic corn with glyphosate (commercial name Roundup). Glyphosate is terrible news for your health. It disrupts your gut bacteria and is considered a “probable carcinogen to humans” by the International Agency for Research on Cancer[*][*].
While there’s no data on the glyphosate contamination rate in xylitol, it’s something to consider if you want to avoid glyphosate in products you consume.
If you’re going to use xylitol, use birch tree-derived xylitol — preferably organic and sustainably sourced.
#4: It Has Unknown Microbiome Effects
Your diet heavily influences your microbiome, for good or ill.
Evidence clearly shows that xylitol has a measurable effect on bacteria in your mouth and gut. In general, xylitol inhibits the growth of bacteria[*]. While that might be a good thing for preventing cavities, it’s an unknown factor when it comes to gut health.
In humans and animals, xylitol consumption tends to reduce the number of gram-negative bacteria and increase the number of gram-positive bacteria[*]. While some gram-negative bacteria like Heliobacter pylori can have adverse health effects, others play an essential role in regulating your gut health[*].
A mouse study found that 40 milligrams of xylitol per kilogram of body weight, equivalent to a 3.24 milligram per kilogram human dose (a dose of approximately 220 milligrams for a 150-pound person) caused measurable microbiome alterations[*].
To summarize, xylitol affects the bacteria in your body, which can influence numerous aspects of your health. The problem is, there isn’t enough evidence to say whether this is a good thing or a bad thing.
#5: It’s Toxic to Dogs
Xylitol is extremely dangerous for dogs. It causes excessive insulin secretion, which leads to severe reductions in blood sugar and almost immediate liver failure. Even small doses of xylitol can quickly become fatal to your pup if left untreated[*][*].
While there’s little evidence to suggest it’s harmful to cats and other pets, it’s still best to keep xylitol out of reach of any animals. Every animal is different, and it’s still possible xylitol could cause liver damage or other adverse effects.
If your pet consumes xylitol, get him or her to the vet as soon as possible. If you act quickly, the chances of survival are high[*].
In humans, a single dose of 20-45 grams of xylitol is generally well-tolerated, but some people are sensitive to the side-effects[*].
If you are sensitive or consume too much xylitol, you’re likely to experience diarrhea, bloating, gas, or other gastrointestinal side-effects.
Most countries consider limited quantities of xylitol safe during pregnancy, but talk to your doctor before adding it to your diet[*].
While xylitol has minimal direct effects on your body weight and blood sugar levels, there are other, better sugar alternatives.
In addition to having unknown microbiome effects, xylitol and other artificial sweeteners can nurture unhealthy cravings that you developed before the keto diet. When you eat sweet foods to reward yourself or deal with stress, your brain lights up similar reward pathways regardless of whether they contain real sugar or a sugar substitute[*].
The best practice if you want to succeed on the keto diet is to cut out most sweet-tasting foods and allow the cravings to go away on their own. Once you develop a healthier relationship with food, you can use sugar alternatives as an occasional way to enjoy foods you don’t usually eat, without exiting ketosis.
Small amounts of xylitol in chewing gum or toothpaste are fine — and may even contribute to better oral health. But stevia and monk-fruit are better natural sweeteners for use in recipes. Unlike xylitol, they don’t have unknown health effects, and can even offer some health benefits.