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So you are following keto, you’re making great strides in your weight loss journey and you have never felt healthier. But from time to time you get this insatiable craving for something sweet.
Walking through a supermarket, everything sugar-laden is screaming out at you and you can forget about the cravings the smells of a bakery can induce…
Back on topic.
Clearly, sugar spikes insulin and as a result all baked goods and sugary treats are not compatible with the keto diet. Naturally, one of the most common questions then asked is are there alternatives that are keto-friendly?
Enter sweeteners. What exactly is a sweetener and can it be used on keto? Or is it a double agent that kicks you out of ketosis and eats into your keto gains? Let’s find out.
Artificial sweeteners
Artificial sweeteners are sugar substitutes, in that they provide a sweet taste without the calories of typical sugar-sweetened products.
These sweeteners differ in that some are metabolised in the body (e.g. aspartame), whereas others are not metabolised, and simply dissolve in the bloodstream and are excreted via urine (e.g. saccharin)[1].
Sweeteners that are metabolised are not technically calorie-free, but they are often hundreds of times sweeter than sugar, meaning a fraction of the calories in sugar are required to sweeten a beverage[1].
When ingested, regular sucrose binds to receptors on the tongue and in the mouth that are responsible for perceiving sweetness.
These ‘sweetness taste receptors,’ binds sugars, but can also bind small molecule sweeteners and sweet proteins to multiple binding sites[2].
Artificial sweeteners closely mimic sugar by binding to the same receptors, which tricks your brain into think that it is consuming something sweet. There are numerous artificial sweeteners with common ones including saccharin, aspartame and sucralose.
Saccharin
Saccharin, popularly known by the brand name ‘Sweet’n’Low,’ is a non-nutritive artificial sweetener (NAS) that is approximately 300 times sweeter than sucrose (sugar)[3]. It is the oldest artificial sweetener, and since its initial use in 1879, has experienced widespread adoption.
As a result, saccharin is commonly used in a range of products, including drinks, baked goods, jams, sweets and chewing gum[4].
Saccharin is water soluble (meaning it dissolves in the blood) but differs from sugar in the sense that it cannot be metabolised.
As a result, it has no nutritive value, meaning it contains no calories.
Instead, saccharin is rapidly expelled from the body via urine, with an excretion half-life of between 1-6 hours[5]. This means that after within 48 hours after consumption, approximately 85% of the saccharin consumed has been excreted[5].
Aspartame
Aspartame is an artificial sweetener accidentally discovered in 1960s, with a sweetness about 200 times that of sugar[6].
Aspartame use is widespread, and is present as a sweetener in thousands of products globally. It is perhaps best known as the sweetener of choice in diet soft drinks such as Pepsi Max and Coke Zero.
Unlike saccharin, aspartame is heat-sensitive and therefore unstable at high temperatures, limiting is usage in certain food products[6].
In addition, aspartame is metabolised in the body. However, the amount of aspartame required to sweeten beverages is very low, and therefore the caloric value is essentially zero.
In the gut, aspartame is hydrolysed by the action of esterase and peptidases, resulting in the formation of methanol (10%), aspartic acid (40%) and phenylalanine (50%)[7].
High concentrations of these metabolites can be potentially toxic, which has brought some controversy around the use of aspartame in consumable products.
Sucralose
Sucralose, commonly sold under the brand name ‘Splenda,’ is a NAS commonly used as a sweetener, and has a sweetness of approximately 600 times that of sucrose[8].
Similarly to saccharin, sucralose is fairly stable at high temperatures, enabling use in a variety of baked and fried goods[8][9]. Sucralose is non-nutritive as it cannot be metabolised by the body, and is therefore calorie-free[8][9].
Sucralose is formed through the chlorination reaction of regular sucrose, during which hydroxyl (-OH) groups are replaced by chloride atoms[9].
This results in the non-nutritive sweetener sucralose, which can then be included in a variety of products to add sweetness without the calories.
Do artificial sweeteners lead to increased insulin secretion and Type II diabetes?
Now that we know what artificial sweeteners are, the next question is, are they keto?
What you will know from reading our article on ketogenesis and ketosis is that in order for a food to be keto, it needs to be low in carbohydrates and not increase insulin levels.
Artificial sweeteners are clearly low in carbohydrates, but given their unique sweetness, some may question whether they truly have no impact on insulin.
Artificial sweeteners viewed as ‘healthier’ sugar substitute
At first glance, it seems that artificial sweeteners are good tool to manage blood glucose levels for diabetics and represent a good alternative to sugar-sweetened products. In fact, Diabetes UK has the following position (December 2018)[12];
“LNCS (Low-no calorie sweeteners) are shown to be safe and they can be used as part of a strategy for adults and children in the management of weight and diabetes. In particular, LNCS sweetened beverages may be helpful when they are used as a substitute by regular consumers of sugar-sweetened beverages and as long as substitution doesn’t lead to later compensation with increased energy intake.” – Diabetes UK
This statement seems to show artificial sweeteners in quite a positive light, but there is a caveat about potential compensation with increased energy intake.
Let’s explore the effects of artificial sweeteners on energy intake compensation and insulin in greater detail.
Impact on glucose levels and Insulin secretion & sensitivity
Artificial sweeteners do not impact glucose metabolism in the short-term
There have been numerous studies that have tested the impact of artificial sweeteners on metabolic syndrome and obesity, both of which are interrelated with insulin sensitivity.
One study examined the impact of aspartame and sucralose on levels of glucose, insulin, active GLP-1 (glucagon-like peptide-1, stimulated insulin secretion) and leptin[13].
They found that after 2 weeks consumption, there were no significant differences in the levels of glucose biomarkers compared to the control group[13].
The study concluded by stating that aspartame and sucralose had no impact on glucose metabolism, with the important caveat that this was a short-term study and the participants were all healthy and had no underlying health conditions[13].
Another study was a systematic review and meta-analysis of randomised controlled clinical trials, investigating the acute glycemic and insulinemic effects of low-energy sweeteners[14].
The study looked at the effect of artificial sweetener consumption and post-meal glucose and insulin levels.
By examining 26 studies, the analysis concluded that the use of artificial sweeteners had no impact on participant glucose or insulin levels, and further, indicated a smaller post-meal glucose response in diabetics consuming sweeteners[14].
Furthermore, it is a common theme of meta-analyses or systematic reviews to find haphazard studies and poor quality evidence for the link between artificial sweeteners and metabolic-related conditions[15].
Emerging evidence that artificial sweeteners combined with carbohydrates lead to impaired glucose response
However, there is emerging evidence that artificial sweeteners, especially when consumed with carbohydrates, lead to increases in insulin secretion and an impaired ability for the body to manage glucose[16].
In one study, obese patients, who were insulin sensitive, underwent a glucose tolerance test, either before consuming the artificial sweetener, sucralose, or a placebo.
The study found that participants who consumed sucralose before the test, had higher peak glucose levels, greater insulin peak secretion rates and lower rates of insulin clearance[16].
This suggests that consuming sucralose can in fact lead to increased insulin levels, not directly, but by hampering the body’s glucose tolerance.
Glucose + artificial sweeteners lead to increased glucose spike
This is supported by further studies that have shown similar results.
A study conducted to examine glucose tolerance levels in patients after artificial sweetener consumption, fed patients either sucralose + glucose or saccharin + glucose and compared this against glucose only participants.
Researchers found that compared to those receiving glucose only, the participants who received the sweeteners had a higher glucose spike, and found that this persisted for longer than the glucose only group[17].
What lends further credibility to the impaired glucose tolerance and metabolism theory is that studies have shown that short-term sucralose consumption alone had no impact on insulin sensitivity in healthy individuals.
However, when combined with sugar, insulin sensitivity was decreased[18].
Clearly, there is emerging evidence that artificial sweeteners could potentially impact glucose metabolism and insulin sensitivity, but longer term, high quality studies are needed to confirm whether this occurs in practice.
At present, it seems consuming artificial sweeteners in the absence of sugar is the better option.
Total energy intake
The beneficial effects of artificial sweeteners have however been questioned. Some people claim that the by removing the caloric component of sweetness, you decouple this process, leading to an incomplete activation of the neural reward pathway[19].
As a result, the calories saved from consuming actual sugar are then reclaimed in the form of increased appetite[19].
They claim this widespread use of artificial sweeteners has lead to global increases in obesity and diabetes[19].
However, the clinical evidence for this theory is currently lacking.
Substituting sugar with sweeteners appears to reduce energy intake in overweight participants
A study conducted on overweight men and women looked to see whether daily supplementation of sucrose or sweetener lead to weight gain on an ab libitum diet.
The study ran for 10 weeks after which, they examined the participants for weight gain and eating habits.
They found that the group consuming sucrose had a greater total energy intake than the sweetener group, as well as consuming more energy from sucrose and carbohydrates.
In addition, the sucrose group lead to increased body mass, whereas the sweetener group reported an overall slight reduction in body mass[20].
Artificially sweetened beverages led to increased energy intake in children
In contrast, a large scale study by NHANES from 2011-2016 found that low-calorie sweetened beverages was associated with an increased total energy and sugar intake in children[21].
A key potential benefit of artificial sweetener consumption is that it is a ‘healthier’ alternative to sugar-sweetened beverages.
In contrast to that theory, the NHANES long-term study showed that there was no difference between sugar-sweetened beverage consumption and artificially-sweetened beverages, when it came to total energy and sugar intake.
The study clearly found that both sugar and artificially sweetened beverage consumption lead to increased overall energy intake compared to children who consumed water[21].
As with much of the research on artificial sweeteners, the evidence is conflicting.
However long-term studies showing that consumption leads to increased overall energy intake in children, should be a red-flag and make people reconsider the utility of artificial sweeteners[21].
So are artificial sweeteners compatible with a keto diet?
Ultimately, artificial sweeteners will not directly lead to an increase in blood sugar and subsequent insulin secretion, and therefore will allow you to remain in ketosis.
However, there is emerging evidence that frequent consumption of these sweeteners could leads to decreased insulin sensitivity and impairments in glucose metabolism.
A key theme emerging form the research is that different patients often respond very differently to sweetener consumption.
For example, differences in insulin sensitivity, age, body mass and BMI may all play a role in the impact of sweetener consumption.
As a result, it is important to moderate intake of artificial sweeteners and look for natural alternatives where possible.
I would recommend avoid artificial sweeteners and instead going for natural sweeteners that can provide you with that hit of sweetness.
>>Why not check out our guide on natural sweeteners that can be used on keto?
