Keto sweeteners – the best and the worst
To the left, in the green zone, are keto low-carb sweeteners that have generally been shown to have little impact on weight gain or blood sugar. To the right, in the red zone, are sweeteners to strictly avoid.
The numbers corresponding to each sweetener represents the known impact each product has on blood sugar and insulin response as compared to the same amount of sweetness as white sugar (100 percent pure sugar.)
The question marks by those products with “zero” represent what is currently known about their impact on blood glucose and insulin response only. These products are relatively new and their full effect on obesity, diabetes, liver health, gut microbiome and long term risk for metabolic or cardiovascular disease is not yet known. More research is needed.1
The products that have numbers with asterisks reflect the fact that these products contain some carbs, in some cases as fillers (typically dextrose). For example, a packet of Splenda provides about the same sweetness as two teaspoons of sugar, which equals 8 grams of sugar. The packet contains about 0.9 grams of carbohydrate (dextrose). That’s 0.9 / 8 = 0.11 times the effect of sugar, for an equal amount of sweetness. Pure 100% sugar has a number of 100, so Splenda gets a number of 100 x 0.11 = 11.
The asterisks by xylitol and maltitol reflect that these products do create a blood glucose and insulin response, although reduced. The number compares that relative response, out of 100, to the equivalent sweetness of pure sugar.
If you are trying to stay in ketosis, avoid the sweeteners in the middle and red zone. Primarily use stevia or erythritol if you need sweeteners – though their long-term health impacts are not yet fully known.
Beware: the sweetener snare
The sweeteners to the left above might only have small or even negligible direct effects on weight and blood-sugar levels. But that’s not the only concern.
Here’s the potential sweetener trap: eating sweet-tasting foods and drinks tends to promote the craving for more sweet-tasting treats. Cravings aren’t kicked to the curb, they’re coddled and kept.
Even the no-calorie sweeteners, like stevia and erythritol, are typically added to foods that mimic or replace the foods that the keto diet eliminates — sugary soft drinks, cakes, cookies, muffins, pastries, ice creams, candies, dessert bars, energy bars, and more. They tend to promote snacking and extra consumption of desserts and treats, typically eaten when not hungry, dramatically raising the risk that you may eat more than you need.
They also keep you tied to old patterns of your former high-carb eating, such as giving yourself sweet rewards that often contributed to weight gain and metabolic issues in the first place. They may slow or stall weight loss or even cause weight gain on the keto diet. They may also trigger a relapse to non-keto eating.
Even the zero calorie sweeteners in diet soft drinks may possibly contribute to long term weight gain and metabolic issues.2 All sweet tastes, whether real sugar or sugar substitutes, act upon the same sweet taste receptors of the tongue and trigger similar brain neural reward pathways that according to researchers, “perpetuate their intake”, so they can maintain sugar addictions and cravings.3
Moreover, zero-calorie sweeteners’ impacts on pregnant women, the developing fetus and young children are unknown and could be potentially risky for long term metabolic health.4 More research is certainly needed.
All of these reasons are why we at Diet Doctor encourage people on a keto diet to ideally avoid all sweeteners, if possible.
We do understand, however, that many people feel they need a sweet treat every-so-often. To face a future devoid of birthday cake and ice cream for some removes some joy from their lives. An occasional sweet treat – especially one made with stevia or erythritol — might sometimes make sustaining the keto diet much easier.
Fortunately, over time, the keto diet reduces cravings for sweet-tasting foods for most people. It gets easier to control or ignore cravings; the desire for sweets diminishes. Many then find that the natural sweet taste of wholesome foods emerge. Taste buds can become more attuned to subtle and rewarding flavours. The desire and need for sweeteners ease.
Using sugar as a sweetener
Real sugar as a sweetener comes in many shapes and forms: white, brown, demerara, icing, confectionary, maple syrup, coconut sugar, date sugar, and more.
Real sugar is a double molecule of glucose (50%) and fructose (50%). That makes sugar 100% carbs, and all these sugars have identical (bad) impacts on weight gain, blood glucose, and insulin response.
On a keto diet, sugar in all its forms is strictly avoided. It will derail your progress. Treat it like poison.
Note that many sweeteners – white or brown sugar, maple syrup, coconut sugar and dates – have a number of exactly 100. This is because these sweeteners are made up of sugar. To get the same amount of sweetness as white sugar, you’ll get about the pretty much an identical effect of these sweeteners, on blood sugar, weight and insulin resistance.
Worse than sugar: pure fructose
What’s even worse than sugar? Fructose. That’s because it goes straight to the liver, promoting fatty liver, insulin resistance, central obesity, and unhealthy lipid profiles. Unlike pure sugar with its pairing of glucose and fructose, sources of fructose are much slower to raise blood sugar and are given a lower glycemic index (GI) rating.5 But don’t let that low GI rating fool you! Fructose is still doing a lot of metabolic harm over the long term — even more than pure sugar.
Fructose sweeteners — high fructose corn syrup, fruit juice concentrate, honey, molasses, agave syrup — are labelled 100+ in our image because of their detrimental long-term impact. They could be called super sugars. Agave syrup is the worst of all, with the highest fructose content.
Zero calorie sweeteners
While all sweeteners have potential for negative impacts, if sustaining your keto journey is helped by the consumption of sweets from time to time, here are the 3 choices that may do the least harm.
Option #1: Stevia
Stevia is derived from the leaves of the South American plant, Stevia rebaudiana which is part of the sunflower family. Indigenous peoples in Paraguay and Brazil used the intensely sweet leaves in teas, medicines and to chew as a treat, most often simply taking fresh leaves or drying the leaves for various uses.
Commercial use and marketing of the natural leaves is not permitted in the US. These days the active sweet compounds, called stevia glycosides, are extracted and refined in a multi-step industrial process to meet with US and European regulatory requirements. The FDA, while not approving the unrefined leaves, has designated the refined extract as “Generally Regarded as Safe (GRAS).”
China is now the leading grower and producer of stevia sweeteners worldwide. The process of production includes more than 40 steps, including bleaching and decolouring.
- It has no calories and no carbs.
- It does not raise blood sugar.
- It appears to be safe with a low potential for toxicity.
- Stevia is very sweet — 200 to 350 times the sweetness of sugar — and a little goes a long way.
- While intensely sweet, it doesn’t taste like sugar.
- Many people find stevia has a bitter after taste.
- It is challenging to cook with to get similar results as sugar and cannot be simply swapped into existing recipes.
- At least one study shows large amounts of stevia may increase insulin secretion and may still drive fat storage and metabolic issues.6
- There’s not enough long term data on stevia to discern its true impact on health of frequent users.7
Sweetness: 200-350 times sweeter than table sugar.
Products: Stevia can be purchased as a liquid, powdered or granulated. Note that granulated stevia, such as the product Stevia in the Raw, contains the sugar dextrose. Some granulated stevia products, like Truvia, also contain erythritol and fillers.
Option #2: Erythritol
Made from fermented corn or cornstarch, erythritol is a sugar alcohol that occurs naturally in small quantities in fruits and fungi like grapes, melons and mushrooms. It is only partially absorbed and digested by the intestinal tract, which can cause gastro-intestinal discomfort in some people.
- It has zero calories and no carbs.
- Its active compound passes into the urine without being used by the body.
- In its granulated form it is easy to use to replace real sugar in recipes.
- It may prevent dental plaque and cavities compared to other sweeteners.8
- It doesn’t have the same mouth feel as sugar – it has a cooling sensation on the tongue.
- It can cause bloating, gas and diarrhea in some people (though not as much as other sugar alcohols).
- Absorbing erythritol and then excreting it via the kidneys could potentially have negative health consequences (none are known at this time).
Sweetness: 70% as sweet as table sugar.
Option #3 Monk fruit
While it’s derived from a round, green fruit grown for centuries in Southeast Asia, it is a relatively new sugar substitute on the market. Also called luu han guo, monk fruit was generally dried and used in herbal teas, soups and broths in Asian medicine. It was cultivated by monks in Northern Thailand and Southern China, hence it’s more popular name.
While the fruit in whole form contains fructose and sucrose, it is non-caloric compounds called mogrosides that provide its intense sweetness, 250 times as strong as sugar, and that can replace sugar. In 1995, Proctor & Gamble patented a method of solvent extraction of the mogrosides from monk fruit.
While the US FDA has not ruled on Monk fruit as GRAS (generally regarded as safe) it has publicly noted that it accepts manufacturers’ GRAS determination.9 In the last few years more than 500 monk fruit products have come to market in the US. Monk fruit has not yet been accepted for sale by the European Union, but approval appears to be pending.
- It has a better taste profile, with less bitterness of after taste, than stevia.
- It is often mixed with stevia to reduce cost and blunt stevia’s aftertaste.
- It is also mixed with erythritol to reduce expense and improve use in cooking.
- It doesn’t cause digestive upset.
- It is expensive.
- It is often mixed with other “fillers” like inulin, pre-biotic fibres and other undeclared ingredients.
- Be careful of labels that say “propriety blend” as it may have little active mogroside ingredients.
Products: Granulated mixes with erythritol or stevia, pure liquid drops, or liquid drops with stevia; also used in replacement products like monkfruit sweetened artificial maple syrup and chocolate syrup.
Low carb: Xylitol
If you chew sugar-free gum, you are usually chewing xylitol. It is the most common-sugar-free sweetener in commercial gums and mouth washes.
Like erythritol, xylitol is a sugar alcohol derived from plants. It is produced commercially from the fibrous, woody parts of corn cobs or birch trees through a multi-step chemical extraction process. The result is a granular crystal that tastes like sugar, but is not sugar.
Xylitol is low carb, but not zero carb. Xylitol’s carbs can quickly add up on a keto diet, so it’s not a great option.
- Xylitol has a low glycemic index of 13, and only 50% is absorbed in your small intestine.
- When used in small amounts, it has a minor impact on blood sugar and insulin levels.
- It has about half the calories, but the same taste as sugar.
- It can replace sugar 1 for 1 in recipes.
- It’s been shown to help prevent cavities when chewed in gum.
- It can cause significant digestive upset (gas, bloating, diarrhea) even when consumed in small amounts.
- It is highly toxic to dogs and other pets – even a small bite of a product made with xylitol can be fatal to dogs.
Sweetness: Equivalent in sweetness to table sugar.
The following sweeteners are quite new and aren’t widely available at this time. Moreover, very little is known about their long-term impacts on health because there isn’t much research on them.
Inulin is a member of the fructans family, which includes a fiber known as fructo-oligosaccharides (FOS). As a fiber, it provides no digestible carbs and isn’t absorbed from the digestive tract. Although it’s found in some vegetables like onions and Jerusalem artichokes, chicory is the main source of inulin used in low-carb sweeteners and products.
Because inulin is rapidly fermented by gut bacteria, it can cause gas, diarrhea, and other unpleasant digestive symptoms, especially at higher intakes.10Indeed, many people have reported these symptoms after consuming inulin-based sweeteners. However, inulin appears to be safe when consumed in small amounts.
Sweetness: 70-80% of the sweetness of sugar
In 2015, allulose was approved as a low-calorie sweetener for sale to the public. It’s classified as a “rare sugar” because it occurs naturally in only a few foods, such as wheat, raisins, and figs. Although it has a molecular structure almost identical to fructose, the body isn’t able to metabolize allulose. Instead, nearly all of it passes into the urine without being absorbed, thereby contributing negligible carbs and calories.
Some studies in animals suggest there may be health benefits to consuming allulose, but human research has been mixed.11 It reportedly tastes like sugar and doesn’t cause any digestive side effects. However, it is much more expensive than other sweeteners and isn’t widely available. Allulose has received GRAS (Generally Regarded as Safe) status from the FDA.
Sweetness: 100% of the sweetness of table sugar
Yakon syrup comes from the root of the yacón plant native to South America. It is a truly “natural” sweetener, similar to maple syrup. However, like inulin, yakon syrup contains fructo-oligosaccharides, which can cause digestive discomfort. It has a lower glycemic index (GI) than most other sugars because a portion of the syrup is fiber. Still, one tablespoon of yakon syrup contains some digestible carbs (sugar). The exact amount can vary, but some estimates put it at around 30 grams.12
Sweetness: About 75% as sweet as sugar.
BochaSweet is one of the newest sweeteners on the market. It’s made from an extract of the kabocha, a pumpkin-like squash from Japan. This extract reportedly has the same taste as white sugar, yet because of its chemical structure, it supposedly isn’t absorbed and contributes no calories or carbs.
Unfortunately, although it has received great reviews online, very little is known is about its health effects because there are few, if any, published studies on kabocha extract.
Sweetness: 100% of the sweetness of table sugar
Beware: deceptive sweeteners
Do you know that some products with labels that say “zero-calorie” sweeteners are almost 100% carbs?
Beware of Stevia in the Raw, Equal, Sweet’n Low and Splenda. They are labeled “zero calories” but they are not.
The FDA allows servings under 1 gram of carbs and under 4 calories per serving to be labeled “zero calories”. So manufacturers cleverly package about 0.9 grams of pure carbs (glucose/dextrose) mixed with a small dose of a more powerful artificial sweetener.
The labels reel in the consumer and satisfy the authorities. But the packages in fact contain almost 4 calories each, and almost a gram of carbs. On a keto diet that can quickly add up. Don’t be conned; don’t consume.
Ditch them for their deceptive marketing alone. Some of the artificial sweeteners, such as aspartame and sucralose, also have lingering health concerns.
Almost as bad as sugar: maltitol
Maltitol is another sugar alcohol. It is made from the hydrogenation of the corn-syrup by-product maltose. It behaves in cooking and production very much like pure sugar so it is very popular in commercial “sugar free” products, such as candy, desserts, and low-carb products. It is also less expensive for food producers to use than erythritol, xylitol, and other sugar alcohols..
Do not consume maltitol on a keto diet. It has been shown to raise blood sugar and increase insulin response. It is not good for anyone with diabetes or pre-diabetes. It also has two-thirds of the calories as sugar.
It is also a powerful laxative. While 40% of it is absorb in the small intestine, the remaining 60% ferments in the colon. Studies have shown that maltitol may cause significant gastrointestinal symptoms (gas, bloating, diarrhea etc.) even in when consumed in moderate amounts.13
Diet soft drinks on keto?
Can you drink diet soft drinks on a keto diet? We recommend you avoid them. Drink water, sparkling water, tea, or coffee instead.
As noted at the start of this guide, regular consumption of sweet substances, even with no calories, will maintain cravings for sweet tastes. Your palate will remain tied to sweet flavours and be less likely to learn to enjoy the natural, flavourful but less intense sweetness of keto foods.
Other health concerns are suspected, but unproven, with many of the artificial sweeteners used, like aspartame, acesulfame K and sucralose.15
If you must drink diet sodas, however, you will likely still stay in ketosis. Regular soda, sweetened with sugar or high fructose corn syrup, will kick you right out of ketosis. Do not consume.
A final word on keto sweeteners
Yes, it’s pretty clear, we’re not a fan of sweeteners. While some sweeteners may be better than others, the best strategy for achieving optimal health and weight loss may be learning to enjoy real foods in their unsweetened state.
A 2017 study found many of the positive research on sugar substitutes are funded by industry and full of conflict of interest, research bias and unreproduced findings.16
It might take a little time for your taste buds to adapt, but over time, you may discover a whole new appreciation for the subtle sweetness of natural, unprocessed foods.
Can’t imagine living without sweet foods? If you try, do you find it almost impossible to curb the cravings? Do you find yourself then binging on sweets? You might be interested in our course on sugar addiction and how to take back control. And yes, you can do it!
Here are three recent reviews making this point:
GI = glycemic index, i.e. how quickly a carbohydrate-containing food results in a blood sugar increase after eating it. ↩
Nutrients 2018: A double-blind, randomized controlled, acute feeding equivalence trial of small, catalytic doses of fructose and allulose on postprandial blood glucose metabolism in healthy participants: The fructose and allulose catalytic effects (FACE) trial ↩
- New research: could non-caloric sweeteners cause weight gain?
- How artificial sweeteners could make us eat more
- Diet Pepsi may cause cancer – consumer watchdog downgrades it from “caution” to “avoid”