In order to stick with your the keto diet, you’ll have to completely cut refined carbs. This means sugars completely eliminating sugars! Transitioning away from sugar may seem impossible but never fear, there are alternatives! As many people on keto still have sugar cravings, sugar-replacements like polyols have become really popular.
But can you really consume polyols on keto?
There has been a lot of discussion surrounding sugar-replacements and polyols have often taken centre stage. In this article, we’ll dive into what polyols are and whether they can be consumed on the keto diet. We’ll also explore the different types of polyols and the potential health benefits and side-effects of consuming them.
Table of contents
What is the keto diet?
The keto diet (ketogenic diet) is a low carbohydrate, high-fat diet. In order to follow keto, you have to restrict carbohydrates (less than ~50g per day), thereby allowing your body to enter the metabolic state of ketosis. By restricting carbs, your body has no choice but to switch to fat for fuel. Fats are then broken down into molecules called ketone bodies, which can be used for energy[1].
In practice, this means eliminating starchy and refined carbohydrates, such as potatoes, rice, pasta and sugar. Instead, the keto diet focusses on high quality fats from a variety of sources, including avocado, salmon and olive oil. In addition to fat, the keto diet encourages a moderate intake of protein, from sources such as meat and eggs[1].
What are polyols?
Are polyols the same as sugar alcohols?
Polyols are organic compounds that contain -OH groups.
When people talk about polyols in the context of nutrition, they are most often referring to sugar alcohols. Sugar alcohols are a type of polyol that are naturally occurring in many fruits and vegetables[2][3].
However, for commercial production, polyols are usually produced through a hydrogenation reaction. This reaction converts sugar into sugar alcohols. While polyols are technically carbohydrates, they are not sugars[3].
Polyols do however produce a sweet flavour, which makes them suitable sugar-replacements. Unlike sugar however, these polyols have significantly reduced calories. The addition of the -OH groups means they can only be partially digested. This means they provide a sweet taste but with significantly fewer calories[2].
Polyols range in sweetness from 30-90% as sweet as sugar
While polyols are sweet tasting, many are only around 50% as sweet as sugar. This means they are often blended with sweeteners of higher intensity to create a sweeter taste profile[2].
The sweet properties of polyols means they are widely used in the food and beverage industry. You’ll often find them in products such as chewing gum, confectionary and soft drinks[2].
For the remainder of this article, the terms polyols and sugar alcohols will be used interchangeably.
Different types of polyols on keto
Ok, so now that we know what polyols are, let’s dive into the different types. As you’ll see, a number of different factors will determine if you can consume certain polyols on keto.
There are a wide variety of different polyols of which 8 have been approved by the FDA for human consumption. These include hydrogenated starch hydrolysates, erythritol, isomalt, lactitol, maltitol, mannitol, sorbitol and xylitol[2][4].
Similarly to artificial sweeteners, not all polyols are created equal. Different polyols contain different amounts of digestible carbohydrate, levels of sweetness and insulinemic indices. All of these factors influence which polyols can be consumed on the keto diet[2].
Hydrogenated starch hydrolysates
Hydrogenated starch hydrolysates (HSH) are mixtures of other sugar alcohols, such as sorbitol and maltitol. HSH are produced from the partial hydrolysis of corn, wheat or potato starch, producing a hydrolysate. This hydrolysate is subsequently hydrogenated at high temperature and pressure[5][6].
HSH is a broad term used for mixtures of different polyols. Due to the sweetness of the polyols in the mixture, HSH can range from 40-90% as sweet as sugar[5][6].
Erythritol
Erythritol is a zero-sugar sweetener which naturally occurs in certain fruits and vegetables[7].
Given its negligible impact on blood sugar and minimal effect on insulin levels, erythritol is a favourite on the keto diet[7].
Altough it naturally occurs in fruits and vegetables, it is commercially produced through fermentation. As it is around 50-60% as sweet as sugar, it may have to be used in slightly greater quantities than sugar[2][8].
Isomalt
Isomalt is another polyol that is used as a sugar-substitute and consists of a mixture of 2 sugar alcohols; gluco-mannitol and gluco-sorbitol[9].
These are produced in a two-step process in which sucrose is converted into isomalt[9].
The resulting isomalt is approximately 45-65% as sweet as sugar and is used in a variety of food applications[2].
Unlike many other polyols, isomalt is stable under higher temperatures. This means it can be used as a sweetener in baked goods, without losing its taste and texture.
Lactitol
Lactitol is a polyol that is manufactured through the hydrogenation of lactose and is commonly used as a ‘bulk sweetener[10].’
As it is only approximately 30-40% as sweet as sugar, lactitol is often mixed with other sweeteners[2].
Lactitol has numerous commercial applications as a sweetener as well as an excipient in medical products. Examples include use in ice cream, chocolate, hard candies and baked goods.
Maltitol
Maltitol is a polyol that is manufactured from the hydrogenation of the sugar, maltose. As it is approximately 80% as sweet as sugar, it is commonly used as a 1:1 sugar-substitute[2].
Like other polyols, maltitol is only partially digested in the body. This means it tends to have lower calories than the same amount of sugar[11].
While maltitol may have a reduced glycemix impact, it still leads to increases in blood glucose. As a result, consuming polyols like maltitol is not recommended on the keto diet[2].
Mannitol
The polyol mannitol is around 60-70% as sweet as sugar and is often used in the food, beverage and pharmaceutical industries. Similarly to erythritol, mannitol occurs naturally in some plants and vegetables, such as mushrooms[2].
Like other sugar alcohols, mannitol is not as sweet as sugar. It is however very heat stable. As a result, it is commonly used in baked goods or those where heat stability is required[12].
Mannitol is also commonly used as an ingredient in pharmaceutical and nutritional tablets, having no discernible affect on blood glucose.
Sorbitol
Sorbitol is a polyol that is commonly used in food applications. It’s only around 60% as sweet as sugar, so it is sometimes blended with other sweeteners to increase the overall sweetness[2].
Similarly to others polyols listed, sorbitol also occurs naturally in small quantities in fruits, such as berries. However, it is normally commercially produced through the hydrogenation of glucose[13].
Sorbitol is commonly used as an ingredient in confectionary but is also used as a bulk sweetener in numerous other applications.
Xylitol
Xylitol naturally occurs in a number of fruits and vegetables.
Interestingly, xylitol can also be produced in small amounts by the body during carbohydrate metabolism[14].
For commercial use however, xylitol is produced from xylose (xylose is obtained from plant biomass)[14].
As xylitol contains reduced calories (compared to sugar), it is commonly used as a sugar-substitute and marketed as a healthier alternative to sugar.
How are polyols digested?
So now that you know what polyols are, the question remains; can you consume polyols on keto?
To answer this question we first need to understand how sugar alcohols are digested.
Polyols are not calorie-free
The first important to point to address is that polyols are not calorie-free. When people hear the word sugar-substitute, they often think of zero-calorie artificial sweeteners. However, most polyols only contain a reduced number of calories and carbohydrates per gram, compared to sugar[2].
Therefore overconsuming sugar-alcohols can lead to weight gain (and gastrointestinal discomfort).
Polyols are digested more slowly than sugar
Due to the chemical structure of polyols, they are significantly more difficult to digest than simple sugars. Certain polyols are more difficult to digest than others, which means intestinal bacteria often digest parts of them[15].
Although polyols are carbohydrates, they are digested much more slowly than sugar. This means they have a significantly reduced impact on blood glucose and insulin levels. However, reduced is not the same as no impact. This is where choice of polyol becomes more important. Choosing polyols with a higher glycemic index are less likely to be suitable for keto[15].
Are polyols keto?
Some polyols have a minimal impact on blood sugar
In order to stay in ketosis, you need to control your blood glucose and insulin levels. Given that some polyols have a negligible impact on blood glucose, they are generally compatible with the keto diet.
This is demonstrated in a study where participants were given a supplement of glucose, erythritol or xylitol. Unsurprisingly, sugar ingestion increased both plasma glucose and insulin levels. However, erythritol had no impact on either plasma glucose or insulin. In addition, there were only minor increases in blood sugar following xylitol consumption[16].
Longer term studies show some polyols have a reduced impact on blood glucose
Similarly, longer term studies have demonstrated an overall improvement in metabolic control.
A 12-week study investigating the impact of replacing sucrose with the polyol isomalt found improvements in markers for metabolic control. The study included patients with type II diabetes and found that those supplemented with isomalt experienced significant reductions in fasting blood glucose and insulin levels[17].
Similarly, another study investigated the impact of chronic xylitol or erythritol consumption. The study found that neither polyol had an affect on intestinal glucose absorption[18].
So, what does all this mean?
Firstly, we can conclude that polyols have a reduced impact on blood glucose and insulin levels. However, it’s important to note that this is in comparison to sugar. So although some polyols are better for blood glucose than sugar, they can still increase your blood glucose.
Polyols with a lower glycemic index are more suitable for keto
Increases in blood glucose and insulin can impact ketosis, as ketosis relies on low levels of carbohydrates. Therefore an increase in blood glucose could switch your metabolism to carbohydrates for fuel. This would kick you out of ketosis[2][19].
We can also see that different polyols have differing impacts. As mentioned earlier, each polyol has a different glycemic index. Higher glycemic indices indicate a higher impact on blood sugar, and those polyols should be avoided. Based on glycemic index, the only polyols without any impact on blood sugar levels are erythritol and mannitol[2].
Another important factor to consider is amount of polyols consumed. Polyols with a higher glycemic index are unlikely to impact ketosis if consumed in small quantities. For example, small amounts of sorbitol in chewing gum won’t kick you out of ketosis.
Overall, choosing the right polyols is important to stay on track with your keto diet. If chosen correctly, certain polyols are keto-friendly.
In order to safely remain in ketosis, we would recommend sticking to erythritol.
How should you calculate polyols on keto?
As mentioned earlier, polyols (sugar alcohols) are classed as carbohydrates. However, due to their reduced glycemic index and caloric value, some polyols are keto-friendly.
But when reading food labels should you include the carb value of polyols or subtract it from the total entirely?
This is where you can use the concept of ‘net carbs.’ Net carbs refer to the total amount of fully digestible carbs in a meal. So for the case of sugar alcohols, it is advised to remove half the number of carbs. For example, if a product contains 8g of sorbitol, you would calculate that as 4g of net carbs[20].
If you want to be stricter, you can fully include the carbs in your calculations. We personally subscribe to the net carbs model, due to the reduced digestibly of polyols.
Should you consume polyols on keto?
Polyols with a low glycemic index are acceptable for the keto diet. But does that mean you should consume them? In addition to being a lower calorie alternative to sugar, polyols are also associated with a number of other health benefits.
Polyols can improve weight control and metabolic profiles
Polyols like erythritol can provide sweetness to foods and beverages but at a fraction of the caloric value of sugar. As a result, using polyols as a sugar-substitute can significantly reduce overall daily caloric intake. This could assist in weight loss[7].
Some polyols also have significantly lower glycemic indices, resulting in greater metabolic control. As a result, some polyols can be used more freely on the keto diet and can even be consumed by diabetics.
Polyols can improve dental health
Use of polyols has also been associated with improved dental health and the prevention of caries. This is the result of replacing dietary sugar with polyols. Reducing the total amount of sugar means reduced plaque formation, therefore limiting damage caused by oral bacteria[21].
Polyols are also able to repair and remineralise dental caries. A number of clinical studies have demonstrated that polyol consumption is strongly associated with re-hardening of caries[21].
As a result, polyols are often recommended as sugar-replacements by dentists, and are commonly found in toothpastes and chewing gums.
Low glycemic polyols are suitable for keto
While sugar should be avoided, we understand that it’s not realistic to completely cut-out sweet foods. As a result, low-calorie sweeteners like erythritol are a great option. While polyols are generally better options than sugar, many of them are unsuitable for keto.
Remember, only those with a minimal impact on blood sugar can safely be called keto-friendly.
Overconsumption of polyols can lead to gastrointestinal distress
While there are a number of benefits to consuming polyols, there are also a number of side-effects to watch out for.
One of the key benefits of polyols, like erythritol, is slower digestibility compared to sucrose. As a result, polyols are often left for intestinal bacteria to digest. However, this can be a double-edged sword.
Overconsumption of polyols can lead to gastrointestinal distress. This is because the bacteria in your gut have to work overtime to break down the polyols. During this process, the bacteria produce gas which can result in bloating and stomach cramps[22].
Other symptoms include diarrhea, as excessive consumption can have a laxative effect. Consumption of polyols on keto is more likely to result in diarrhea than on a Western traditional diet. This is likely due to intestinal reduced water absorption on a low carbohydrate diet.
The degree of digestive distress is often related to the digestibility of the polyols consumed. Polyols that are more challenging to digest will likely result in more side-effects[22].
What is overconsumption of polyols and how much can you consume?
So, certain polyols that do not impact your blood glucose can be consumed on the keto diet. However, how much should you eat?
Current recommendations suggest 10-15 grams per day of polyols should be fairly well tolerated. Anything in excess of this amount could constitute overconsumption[23].
While 10-15 grams is recommended, some people are more sensitive to polyols. If you’re just starting out on keto and introducing polyols to your diet, we suggest slowly introducing them to give your body time to adjust[23].
Wrapping up - its fine to consume certain polyols on keto
Polyols (sugar alcohols) such as erythritol can be great options to add some sweetness back into your diet. It’s important to notice that not all polyols are created equal. In order to maximise the success of your keto diet, we’d recommend sticking to erythritol. This is because it has zero impact on blood glucose, zero calories and is naturally occurring.
However, polyols are not the only way to add sweetness to your keto diet. Other natural sweeteners such as stevia and monk fruit are also keto-friendly options that can be used as sugar-substitutes.
Similar to polyols, it is recommended to slowly add other sweeteners into your diet to allow your body to adapt.
>>Check out our guide on natural sweeteners on the keto diet
