Sugar alcohols, or polyols as they are known scientifically are a naturally occurring hybrid macronutrient. The hybrid part comes from the fact that they are a compound of modified carbohydrate and alcohol molecules, minus ethanol. These compounds are found in nature in many common food sources such as fruit. Some sugar alcohols, such as xylitol, are produced naturally in the body in trace quantities.

Modern science has allowed for the mass production and industrial use of sugar alcohols as a sugar substitute. Sugar alcohols are commonly found as a replacement for sucrose (table sugar) in sugar free foods and are even sold in their bulk, pure form as is common with xylitol. Products which aren't food, but are administered through the mouth such as oral care products (toothpaste, mouthwash) and medicinal drugs often contain alcohol sugars as a sweetening agent. This is because alcohol sugars give a similar sweetness as sugar, while providing no Nutritional value to odor and disease causing bacteria in the mouth.

Sugar alcohols are close in sweetness to carbohydrate sugars but have significantly lower caloric values. There are several alcohol sugars commonly used for human consumption. These are:

Xylitol
Sorbitol
Mannitol
Erythritol
Maltitol
Lactitol
Isomalt
Hydrogenated starch hydrolysates

Whichever one you look at, sugar alcohols are not sugars, which means they are not carbs, which means for a carb free diet, such as keto, they are perfect right? Well, not necessarily. Although sugar alcohols aren’t exactly carbs, they are mostly derivative of carbs and sugars and therefore may possess some of the qualities of sugars that directly contradict the goals of a keto lifestyle.

Some sugar alcohols have a high GI value. This stands for glycemic index. It is the measure of how fast a food item raises the registered blood glucose level. Foods with a high GI lead to a fast uptick in registered sugar levels, whole foods with a low GI do the opposite. For an optimal keto lifestyle, you want to aim for low or no GI sources.

Having said that, let's have a look at which sugar alcohols are actually keto friendly.

Best and Worst Sugar Alcohols for Keto

Xylitol

The most popular sugar alcohol available, xylitol is commonly used as a sugar substitute in many low carb or sugar free foods and is also the go to sweetener in pharmaceuticals and oral hygiene products.

It gains its popularity from the fact that it is considered just as sweet as sugar but with almost half the calories.

Xylitol has a low glycaemic index (the measure of the rate of increase of blood sugar a particular food has), meaning it stands in favour of a ketogenic lifestyle.

Just don’t feed it to your dog. Xylitol is a known lethal toxin when it comes to dogs.

Maltitol

Another popular sugar alcohol is Maltitol. It’s popularly used as an alternative in sugar free treats and confectionery. Foods like ice cream, candy and chocolate aimed at a sugar free consumer will often have malitol in the ingredients list.

It has a sweetness factor very close to that of sugar, some describe it as being 75% as sweet as sugar. It also sits low in caloric value, almost having just half the calories of normal sugar.

The drawback with malitol is that it has a relatively high GI when it comes to sugar substitutes. When consumed, it registered a marked increase in blood glucose which doesn’t accommodate a keto-centric diet.

Sorbitol

Sorbitol is a common ingredient in chewing gums, especially those aimed at optimizing dental and oral health.

It naturally occurs in fruits such as prunes. Sorbitol is also known as one of the most laxative sugar alcohols. That’s why prune juice is a popular treatment for constipation.

Sorbitol does unfortunately have a high GI and is therefore a compromise towards a strict keto diet.

Erythritol

Erythritol is a special little molecule. It has a sweetness very close to sugar but also manages to have an almost non-existent caloric value.

It is common in low calorie and carb free foods due to it having 95% fewer calories than sucrose. This insanely low energy value also lends itself to having almost negligible GI value.

All this makes erythritol the best sugar alcohol for a keto conscious diet.

Things to consider.

While having a notable GI may be a turn off when it comes to a keto-centric diet, you need to be aware of other side effects that come with sugar alcohols. Many of the sugars in this list pass through the small intestines straight through to the large intestines. Here, the plethora of different gut bacteria get to work metabolize the sugar alcohols, leading to fermentation. This causes bloating and even diarrhea. It's worth moderating your consumption of sugar alcohols, no matter how keto friendly they are.

In Conclusion.

As much as sugar alcohols may appear as the perfect escape for a keto fanatic, it isn’t so cut and dry. While most offer a low calorie alternative to carb based sugars, the effect some have on your blood glucose quickly puts any attempt at a successful keto protocol at rest. Be mindful and use what works. It also doesn't hurt to consult a nutritionist.