HOME » ARTICLES » Are keto sweeteners safe?

Are keto sweeteners safe?

Last updated Apr 19, 2019 at 3:59PM | Published on Apr 7, 2019

Written by Sarah Neidler, PhD

Scientifically Reviewed by Raphael Sirtoli 

Sweeteners are a bit of a controversial topic in the keto world. Why? Usually, people say that eating sweet-tasting foods and drinks will increase sugar cravings. Others say that no, the occasional sweet treats can make it a lot easier to stick to a keto diet.

Many people who follow a ketogenic diet just don’t really want or need any sweets. While it is true that a keto diet reduces cravings for sweet tasting foods, some of you still enjoy something sweet from time to time.

The world of sweeteners can be confusing. They come with many different names, flavors and belong to different groups. There are artificial and natural sweeteners and also sugar alcohols. What’s the difference and does it matter? Read further to find out which sweeteners are safe and keto-friendly.

Artificial sweeteners

Artificial sweeteners are synthetic sugar substitutes [1]. Because they are several hundred times sweeter than sugar, they are used tiny amounts than sugar. The glycemic index of different sweeteners can vary a lot, but in the tiny amounts they are used, they usually don’t raise blood sugar. They may cause small amounts of insulin to be released, but this effect is also very moderate [2][3][4].

infographic showing the change in blood glucose and insulin after using artifcial sweeteners vs sugar

The most popular artificial sweeteners are:

  • aspartame
  • sucralose
  • saccharin

Always be careful to buy the version that’s not mixed with dextrose, (another word for glucose).

Are they healthy?

Artificial sweeteners don’t have a stellar reputation. Aspartame is the best-studied one, and its consumption is said to be associated with an increased risk of cancer, obesity, heart disease, gastrointestinal issues…the list is long [5][6][7].

Is it true?

The word “associated” is already a good hint that most of this information comes from epidemiological and not from from randomized clinical trials that may be able to show causality [8].

People who are overweight tend to consume a lot of low-to-no calories artificial sweeteners. Why? Typically because they are told that they have to decrease their calorie intake. That’s the typical chicken-and-the-egg problem. Are they obese because they eat a lot of artificial sweeteners? Or are they eating lots of artificial sweeteners because they’re obese?

Remember, obesity is also associated with an otherwise unhealthy lifestyle: lots of fast food, high sugar (despite the use of artificial sweeteners) and a sedentary lifestyle. Using associational studies alone, we cannot know which of these factors contribute to obesity and other health issues like inflammation, increased risk of cancer, and cardiovascular disease [9][10].

There are also animal studies that show that artificial sweeteners can cause health problems, but mainly when given in ridiculously high amounts.

Let’s have a closer look at the best studied artificial sweetener – aspartame. What is it made of? Even though aspartame is of a synthetic product, it’s actually just the fusion of two standard amino acids, aspartic acid and phenylalanine [11]. Amino acids? Correct, the building blocks that we need to build proteins – and we usually don’t think of them being unhealthy. Once aspartame has reached your gut, it is already broken down to these two amino acids, indistinguishable from other “natural” amino acids floating around.

So what does the science say about aspartame effects on health?

One systematic review of studies in rodents found that high aspartame intake has a carcinogenic effect and significantly reduces life span, but only at a  daily dose of 4,000 mg per kg body weight [12]. Lower doses had no impact. For an 80 kg man, that 4,000 mg per kg body weight dose translates to 320 g or roughly 600 liters of diet coke ! Hardly a fair comparison.

As an acceptable daily intake (ADI), the FDA recommends to consume no more than 50 mg per kg body weight per day.  For an 80 Kg man, this translates to 4,000 mg aspartame or roughly 32 cans of diet coke (7.5 liters). That’s still plenty, few people will drink that much of it.

There are very few randomized studies in humans that show adverse health effects of artificial sweeteners. One example is a study with 28 healthy subjects who were randomized to either follow a low (10 mg/kg) or high aspartame (25 mg/kg) diet for eight days. This translates to 16 cans of diet coke or roughly 3.7 liters for an 80 kg man.

Participants in the high aspartame group had a significantly higher level of depression. The researchers noted that the sample size was very small and that the results are in conflict with other studies [13].

On the other hand, there are several systematic reviews and randomized studies that conclude that aspartame consumption does not increase the risk of cancer, or causes high blood pressure, weight gain, increase in appetite, high cholesterol, and triglyceride levels [14][15][16][17][18][19].

We at Nutrita recommend eating nutrient-dense foods (e.g. eggs, steak, salmon) and avoiding many processed foods (e.g. pasta, bread, pastries, sweets). However, some processed foods can also feature in a healthy diet (e.g. salami, cheese, cacao flour, coconut flour). As long as they don’t displace too many of the nutrient dense foods and you don’t immune reaction to them, they tend to be OK.

Some artificial sweeteners may be fine as well. And if they don’t agree with you, it tends to show up as symptoms of digestive discomfort (if you’re paying attention to that). You can check your blood sugars and blood ketones with KetoMojo’s hand-held device. if you really have a hard time believing some artificial sweeteners don’t raise blood sugar or raise insulin.

Sucralose for instance has been shown to not raise blood sugars, blood insulin, nor the gut-signaling hormone (incretin) GLP-1.

No one can say what consuming ridiculous amounts will do to you, but on the other hand, they appear safe when consumed in reasonable quantities. Think honestly about whether consuming artificial sweeteners will help or hinder your efforts to get over your sweet cravings, – if you are still struggling with that. If you don’t know, experiment by introducing and removing them from your diet for a month or so, changing as few other things as you can.

If you are a sugar junkie and can’t live without Coca-Cola, what’s the alternative? Several liters of coke with lots of sugars of known to cause great harm.

Contrary to artificial sweeteners, the health threats of sugary soft drinks are very well established. If you drink several liters of them every single day, they will cause a lot of health issues in no time. Weight gain, fatty liver, insulin resistance…to name a few [20][21][22][23].

Bottom line: they are indeed healthier choices than artificial sweeteners, but compared to vast amounts of sugar by far the better option. Their impact on blood glucose and insulin levels is negligible, so they are safe for ketosis [24].

Did you know?

Infographic showing pancreas artificial sweetener recptors

Sugar alcohols

Sugar alcohols are chemically similar to sugar. Because they bind to sweet taste receptors on the tongue, we perceive them as sweet. They are, however, partially resistant to digestion and as a consequence, do not raise blood sugar to the same extent as glucose.

These sugar alcohols are commonly used as a sugar substitute:

  • xylitol
  • erythritol
  • maltitol
  • sorbitol, isomalt, glycerol, lactitol…

Xylitol

Xylitol occurs naturally in fruits and vegetables. Its sweetness and taste are comparable to regular table sugar. It can be used like sugar in the kitchen and is, therefore, a popular sugar substitute. Xylitol can be metabolized and used as energy, but it has 40% fewer calories than sugar. It, therefore, does impact blood glucose and insulin levels, but to a lesser extent than sugar [25][26].

Xylitol is often found in chewing gum because they are beneficial for the teeth. Harmful bacteria in the mouth try to break them down as they usually do with sugar, but they are not able to “crack” them, they starve.

Downside: Xylitol may cause some stomach discomfort, so be careful when you are not used to it. It is also very toxic dogs in small doses. If you are a dog owner, you better avoid using xylitol.

Erythritol

Erythritol is also found in fruits and vegetables. It is very popular among low-carbers because it has very unique properties: it is very resistant to digestion, which means that it basically just passes the body and leaves it in the same state it came in. It has virtually no impact on blood sugar and insulin levels and is totally safe for ketosis [27][28].

It is usually well tolerated and causes less digestive issues than xylitol.

Downside: it only has 70% of the sweetness of sugar and creates some cooling sensation on the tongue, which some people don’t like. If you use it in moderation, the cooling taste is less obvious, but your dish will also be less sweet. As the sweet sensations change on a ketogenic diet, this is usually not a problem. If you still like it very sweet, you may want to mix the erythritol with something that has more sweetness, such as stevia.

Tip: Erythritol does not dissolve as well as sugar. It’s less of a problem when you use it in hot beverages such as coffee or tea, but it can make your cake or cold dessert crunchy. Just use your blender to grind it, and the problem is solved!

Maltitol

Maltitol is commonly used in sugar-free products. Because maltitol is partly broken down to sugar, it does raise glucose and insulin levels somewhat [29]. It has only 80% of the sweetness of table sugar, so you need it in high amounts. When trying to control blood sugar, keeping insulin low or staying in ketosis, you may want to avoid or drastically reduce the amount of maltitol containing products you consume.

Maltitol tends to cause digestive discomfort to a greater extent than xylitol and erythritol.

Other sugar alcohols

There are more sugar alcohols, such as sorbitol, isomalt, glycerol and lactitol, but we don’t recommend them. They either cause a lot of digestive stress, or rise sugar or insulin levels [30][31][32][33].

Are they healthy?

Sugar alcohols are not as well studied as artificial sweeteners, but until now, they seem to be largely safe. In different words, because their popularity is quite new, they haven’t had enough time to acquire a bad reputation.

Erythritol and Xylitol are very trendy among health-conscious low-carbers. The huge benefit of this? It is easy to find low-carb foods where erythritol or xylitol is the only sweetener and are part of a short list of acceptable ingredients.

Natural sweeteners

These natural sweeteners may be used on a low-carb or ketogenic diet:

  • Stevia
  • Monk fruit
  • Allulose
  • Inulin
  • Tagatose

Keep in mind that ‘natural’ doesn’t tell you anything about whether or not something is healthy for you. It simply indicates where it came from or how it was produced.

Stevia

Stevia is extracted from the leaves of the plant with the name Stevia rebaudiana. It is 300 times as sweet as table sugar and therefore used in minimal amounts [34]. It has no calories and does not impact blood glucose or insulin levels.

You have to be careful not to use too much of it, as it will make your food taste bitter. You can easily combine stevia with erythritol: individually they both have a distinct taste, but in combination, their aftertastes cancel each other out and give a pleasant sweet taste.

You can buy stevia as a powder or a liquid. In either case, make sure that stevia is the only ingredient (unless you get a stevia/erythritol mix). Many stevia products contain fillers, such as dextrose or maltodextrin, which increase blood sugars.

Monk fruit

Monk fruit is a Chinese fruit that has been used in traditional Chinese medicine to treat cough and sore throat and is also thought to increase longevity.

It is about 300 times sweeter than sugar and does not contain any carbs or calories [35].

Downside: It has a bit of an unpleasant and bitter aftertaste. It may help to combine it with other keto-friendly sweeteners such as erythritol or stevia.

Allulose

Allulose is a naturally occurring sugar found in wheat and some fruits. Because our body is not able to metabolize it (use it as fuel), it has almost no calories and a glycemic index of 0.

Its properties are similar to sugar, but it is only 70% as sweet as table sugar [36]. It does not cause digestive problems. The FDA rates allulose as GRAS (Generally Regarded as Safe).

Inulin

Inulin is a natural sweetener that is found in onions, Jerusalem artichokes, and chicory. It belongs to the family of fructans, a fiber that is known as fructooligosaccharides (FOS).

It usually is not digestible, but it is quite sensitive to high temperatures. At temperatures above 275 degrees Fahrenheit (135 °C) in starts to degrade into fructose molecules which can be metabolized. For this reason, it is better to use inulin only for cold desserts.

Inulin is safe when used in small amounts, but can cause digestive problems when used in higher amounts. It has only 35% of the sweetness of sugar but is a welcome addition to sweet dishes because it gives a creamy, smooth texture [37].

Tagatose

Tagatose is found in fruits, cacao, and dairy. It is almost as sweet as sugar and has minimal effects on blood sugar and insulin levels [38]. It is therefore considered as keto-friendly when used in reasonable amounts. It can be used like regular table sugar.

Yacon Syrup

FOS is found in several plants, but the Yacon plant has the highest FOS content. Yacon syrup is extracted from the starchy, fruit-like roots that taste sweet.

The carb content is variable, but the syrup contains about 25% digestible carbs in the form of sugar [39]. Because it is less sweet than sugar, it cannot be used as the only sweetener in a dish without using it in high amounts, which is problematic due to its relatively high carb content. If you don’t mind your dessert not being sweet (quite likely when you have been keto for a while), you can use it as the only sweetener in small amounts. However, it is rather considered as not keto-friendly.

As in inulin, the FOS in yacon syrup are temperature sensitive, and it should be used only for cold dishes.

BochaSweet

BochaSweet is extracted from kabocha, a Japanese squash. It is a very new sweetener and not well studied. It contains a pentose sugar, which according to the manufacturers, is not digestible and has, therefore, zero net carbs [40]. Whether this is 100% true is not clear, but the effect on blood sugar and insulin levels seems to be minimal.

It tastes like sugar and has the same sweetness as sugar.

Other natural sweeteners

There are more natural sweeteners, but because they are not keto-friendly at all, we’ll not discuss them here. You will find fruit juice (concentrate), honey, maple syrup, agave syrup, and coconut sugar as sugar alternatives. Since they are not better than ordinary table sugar, and sometimes worse, just ignore them completely.

Glycemic index

How useful is it to consider the glycemic index when choosing a sweetener? The glycemic index can be very misleading and is not very useful in real life. But let’s first clarify what the glycemic index is. The glycemic index indicates how a certain amount of carbs (usually 50g) affects the blood sugar level over the next two hours compared to the equal amount of glucose [41].

Other than its carb content, the texture and viscosity of a food impact it glycemic index . For instance, starchy foods that remain whole and are not ground down into a flour usually have a lower glycemic index. This is because they tend to raise blood sugar more slowly than they would as a flour that digests quicker.

Remember though, foods with a low glycemic index can still have a high glycemic load, which isn’t better at all. The glycemic index is an imperfect measure.

Let me give you an example: boiled carrots and milk chocolate have roughly the same glycemic index: carrots 39 and chocolate 40 [42]. But carrots contain only 5.2 g net carbs and chocolate 56 g net carbs per 100g [43]. To achieve 50 g carbs, you have to eat roughly 90 g of chocolate (easily doable for most people) or almost 1 kg of carrots, probably easier for a horse than a human to do.

When it comes to the glycemic index of sweeteners, there is an even bigger problem: fructose. Because fructose does not directly increase blood sugar, sweeteners that are high in fructose have a low glycemic index. Fructose, however, is metabolised differently. It goes straight to the liver, and high fructose consumption is the number one cause of non-alcoholic fatty liver disease (NAFLD). People with NAFLD are nearly always insulin resistant on a standard Western diet, a serious health problem in and of itself.

Fructose-containing sweeteners such as high fructose corn syrup, fruit juice concentrates, agave syrup, molasses, and honey may have a lower glycemic index than table sugar, but you should avoid them by any means. Even though fruit juice and honey may be thought of as more “natural” than other sweeteners it does not mean that they are any better for your health.

Can natural & artificial sweeteners and sugar alcohols affect ketosis?

The short answer: yes, they can affect ketosis. Some are keto-friendly, others should be avoided when following a ketogenic diet.

Essential criteria are their carb content, sweetness and effect on the hormone insulin – which is hard to measure! The carb content should be as low as possible. If the sweetness is several hundred times as strong as sugar, they are used in tiny amounts, and the carb content is, therefore, less critical.

The glycemic index is not very useful because it does not consider the amount at which a substance is typically used. If 50 g of something considerably raises blood sugars but it’s so sweet that you only need 1g of it for your cake, a high glycemic index is not a problem. Also, if the glycemic index is high and the amounts you’ll use are substantial, it’s best to avoid it.

What’s important is how much does the sweetener raise your blood sugar and insulin levels when used in realistic amounts.

This leaves us with two groups of keto-friendly sweeteners:

  1. The carb content is considerably lower than in table sugar, but the sweetness is comparable to sugar or less: in this group, you find the sugar alcohols erythritol, xylitol and also some of the natural sweeteners such as inulin
  2. They may, or may not have carbs, which hardly matters because they are so sweet that they are used in tiny amounts. In this group, we have the artificial sweeteners aspartame, sucralose and saccharin and also stevia and monk fruit as a natural sweeteners

Conclusion

When you follow a ketogenic diet, your cravings for sweets will almost disappear. When you are not keto-adapted yet and still fighting with sugar cravings, eating a lot of sweets is somewhat counterproductive, even if it’s made with keto-friendly sweeteners.

Some sweeteners that are safe for ketosis, but the problem is somewhat psychological. They lead you to believe that the food contains something that it doesn’t. Something that tastes sweet in nature (such as fruits) has an entirely different nutrient composition than artificially sweetened things. This misleads your taste sensation, may accelerate sweet cravings and let you make poor food choices.

On the other hand, even after following a keto diet for a long time, there might be occasions which you really want to celebrate with a piece of cake. There is nothing wrong with a keto-friendly sweet treat from time to time. They don’t exactly help you to achieve maximum nutrient density, but as long as your diet is otherwise packed nutrient-dense food, this is not an issue.

Did you like our post?

Share it with your friends!Red Heart on Facebook 2.2.1

Written by Sarah Neidler, PhD

Sarah Neidler did her PhD in cancer research at the Beatson Institute for Cancer Research in Glasgow. She has a strong interest in nutrition and the ketogenic diet and believes that they are beneficial for the treatment and prevention of chronic conditions, such as heart disease and diabetes. She loves cooking, reading, sewing, Yoga, and CrossFit.

Related Articles