The truth behind artificial sweeteners

The sugar tax, introduced in the UK in 2018, has resulted in many brands reducing the sugar content of their products and replacing some of it with artificial sweeteners. Obesity and related conditions such as diabetes and cardiovascular disease are on the increase and eating sugary foods is a significant contributor to these conditions. Thus the use of artificial sweeteners may seem like the perfect solution in the fight against obesity – a sweet taste with little or no calories – and artificial sweeteners are advocated by many organisations including the American Dietetic Association.1

However, the increasing use of sugar alternatives, which started in the 1950s, has had no impact on the incidence of diet and lifestyle-related conditions such as obesity and diabetes.  Furthermore, artificial sweeteners may be having a negative effect on our health. Although they are considered safe by many government organisations, in this blog we review research studies that indicate the use of artificial sweeteners may be detrimental to health.

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Types of artificial and natural sweeteners

There are a number of artificial sweeteners (AS) used in diet and sugar-free marketed products, summarised in the table below. Some are also available to buy as ‘sweeteners’.2

Aspartame Aspartame was discovered in 1965 by James Schlatter, a chemist. It is an artificial, non-saccharide sweetener, found in a number of branded products including Equal, Nutrasweet, and Canderel. It provides approximately 4 calories per gram which is very similar to that of sugar, however it is considered to be approximately 200 times sweeter than sugar and so smaller quantities are used. It cannot be used in baked products as it can be damaged by the heating process.
Acesulfame-K Acesulfame—k was developed as a sweetener by Hoechst in 1970. It is approximately 120 times sweeter than sugar and is heat stable, so can be used in cooking and baking. It may have a bitter after-taste when used alone to sweeten food or beverages therefore it is often blended with another sweetener (usually sucralose or aspartame), whereby each sweetener masks the other’s after-taste and creates an additive effect so that the blend is sweeter than each of its components.
Sucralose Sucralose was discovered in 1976. This non-nutritive sweetener (calorie free) is made from sucrose. Sucralose is 450–650 times sweeter than sucrose (table sugar).
Cyclamate Cyclamate was discovered in 1937. It was used as a low calorie sweetener in the United States in the 1950s and 1960s. It is 30 times sweeter than sucrose.
Stevia Stevia is a natural herb. This zero calorie sweetener mainly contains steviol glycoside which is 10–15 times sweeter than sucrose. The human body does not metabolise these sweet glycosides so obtains no calories from stevia. Unlike artificial sweeteners, the sweet glycosides do not break down in heat which makes stevia stable for cooking and baking.


Xylitol is a naturally occurring five-carbon sugar that tastes and looks exactly like sugar. It does contain some calories but has no effect on blood sugar levels and therefore is regarded as suitable for diabetics (in small quantities).

Although avoiding sugar is an excellent idea and has been shown to have multiple benefits to health, particularly by helping to stabilise blood sugar levels and decrease insulin levels, opting for sugar alternatives can still have metabolic effects particularly on glucose tolerance and therefore has been shown to exacerbate insulin resistance. Several studies have suggested that counterintuitive links may exist between the consumption of artificial sweeteners and the metabolic conditions which they are designed to ameliorate.3 There are a number of reasons for this association:

Glucose Intolerance

Normally a sweet taste signals the body to expect caloric consequences; however this doesn’t happen with AS consumption. Research suggests that this can trigger overeating and exacerbate sweet cravings, as the body is expecting energy delivery but doesn’t get it! In addition cells may be less sensitive to calories from sugar when they are consumed; as a result, when real sugar is consumed, blood sugar rises higher, the thermic effect of food is not as pronounced, feelings of satiety are weaker and this again initiates over-eating4.

It has been demonstrated that artificial sweeteners inhibit the peptide GLP-1 (glucagon like peptide 1) which is synthesised and released from cells in the intestine in response to food intake. GLP-1 has been shown to slow down the rate of gastric emptying, to stimulate secretion of and act in concert with insulin to suppress the release of glucagon from the liver and stimulate uptake of sugar from the blood. It also has protective effects on the cardiovascular system. This interference in the release of GLP-1 results in short-term effects on blood glucose homeostasis and food intake, along with longer-term effects on cardiovascular function.5,6

“Artificial sweeteners can interfere with basic learning processes that serve to anticipate the normal consequences of consuming sugars, leading to overeating, diminished release of hormones such as GLP-1 and impaired blood glucose regulation.”4

Any sweetener which provides a sweet taste with low or no calories (even natural ones such as stevia) can act in a similar way and thus over prolonged time increase insulin levels and potentially lead to weight gain. In addition, studies have shown that the consumption of artificially hyper-sweetened foods and beverages in childhood may be particularly problematic and affect sweet preferences that persist into adulthood.4

Other studies have supported this by showing that aspartame and saccharin intake can impair glycaemic and insulin responses, and are associated with hyperinsulinemia, impaired insulin tolerance, worsening atherosclerosis and weight gain.3 Of particular concern are diet soft drinks as they are not consumed with additional nutrients and therefore may intensify the effects of glucose intolerance.

In summary, the intake of artificial sweeteners has a significant impact on normal regulation of blood sugar. Their use does not aid weight maintenance or weight loss and could potentially contribute to weight gain in the long term.

Effects on the gut

Studies have shown that food choices, including AS consumption, can have a significant impact (and alter) the composition of the microbiome and this is a contributing factor in many conditions including weight gain, cardiovascular disease, diabetes and metabolic syndrome3:

  • Sucralose consumption was associated with under-representation of several commensal members of the rat microbiome;
  • Saccharin was shown to alter the aerobes-to-anaerobes ratio in the rat microbiome;
  • AS consumption is associated with the presence of certain taxa, including expansion of the Actinobacteria phylum, the Enterobacterialesorder, and of various taxa from the Clostridiales order, which are associated with obesity and promotion of gluconeogenesis;
  • Saccharin intake contributes to glucose intolerance which is ameliorated following antibiotic treatment suggesting that the mechanism is via changes to gut microflora;
  • Growth of beneficial Lactobacillus reuteri strains was inhibited in the presence of stevia sweeteners stevioside and rebaudioside A.8

Therefore evidence suggests that artificial sweeteners induce glucose intolerance, in part, by altering the composition of the microbiome.9

Other effects of artificial sweeteners

It appears that all artificial sweeteners have, to some degree, an effect on glucose tolerance and the microbiome, as described above. Furthermore, research has identified additional health concerns:

Aspartame and oxidative stress

Aspartame consumption may increase oxidative stress:

  • An increase in antioxidant enzyme activity was observed alongside an increase in lipid peroxidation and free radical generation;
  • This was additionally associated with a significant decrease in reduced glutathione, glutathione reductase and protein thiol, therefore indicating an increased production of free radicals;
  • High levels of methanol (a by-product of aspartame breakdown) in the blood were noted; methanol in brain regions is related to high levels of oxidative stress.10 Long-term exposure to aspartame has been connected with neuronal death and neural toxicity, this is likely to be in part due to the increase in free radical and oxidative damage.

“This study provides scientific evidence to conclude that aspartame is toxic to body systems, particularly in the brain, it increases the free radicals and triggers apoptosis. Aspartame consumption in a long-term basis may affect the brain.”11

Artificial sweeteners and the brain

Further studies reported that aspartame may induce apoptosis of neurones and have an effect on brain function. These results showed that aspartame12:

  • At a high dose caused a disturbance in ionic homeostasis and induced apoptosis in the brain;
  • Significantly decreased dopamine in the corpus striatum and cerebral cortex and of serotonin in corpus striatum;
  • Significantly alters tyrosine hydroxylase activity and amino acid levels in the brain, therefore affecting neurotransmitter production;
  • May affect electrolyte homeostasis and monoamine neurotransmitter synthesis, in a dose-dependent manner.

Aspartame can also increase plasma levels of the amino acid phenylalanine, which is a derivate of aspartame. Phenylalanine can be neurotoxic and can affect the synthesis of inhibitory monoamine neurotransmitters, the phenylalanine in aspartame could conceivably mediate neurologic effects.13

Similarly, studies have shown sucralose intake is associated with an increase in oxidative stress in the brains of rats exposed to it. Therefore sucralose may attenuate normal cognitive function and neuronal health.15

Artificial sweeteners and the environment

Of equal importance to the direct effects AS may have on our physiological health, is that they may be affecting the health of the environment. As some AS, such as sucralose, work by avoiding absorption and degradation in the body they may be excreted and remain in waste water. A study into the degradation of sucralose showed that biodegradation of sucralose in waterworks did not occur significantly. In addition free chlorine, ozone, and ferrate treatment did not show any potential to degrade sucralose in water. Therefore sucralose is poorly degraded and has the potential to accumulate in the environment, this could lead to an increased intake of sucralose, whether artificial sweeteners are ingested or not, and may have effects on wildlife.14


A number of studies provide evidence that artificial sweeteners significantly affect glucose homeostasis, digestive flora and function and cognitive health.

Even after controlling for a wide range of key potential confounders, studies in humans have found significantly increased incidence of depression, metabolic syndrome, diabetes, cardiovascular events, cardiovascular mortality, and total mortality among frequent users of the most-widely-used LCS (low calorie sweeteners) vehicles – diet sodas and other diet beverages – and these results are troubling.”2

Therefore it can be seen that although sugar is a major contributor to long-term chronic diseases and obesity, artificial sweeteners are not the ideal solution to this and their use should be avoided. It is more advisable to choose foods that are naturally low in sugar and which stabilise blood sugar levels.

Key takeaways

Artificial sweeteners:

– Interfere with a normal response to calorie intake and can trigger overeating;

– Inhibit the release of a hormone called GLP-1 (Glucagon like peptide 1) which is important for supporting glucose balance, insulin sensitivity and protecting against cardiovascular disease;

– Further contribute to glucose intolerance by disrupting the composition of our gut microbes. This disruption may result in further negative effects on general health.

  • Aspartame and sucralose have been shown to increase oxidative damage and reduce brain chemicals (neurotransmitters) and therefore may contribute to poor cognitive function and depression.
  • Sucralose is very difficult to biodegrade and therefore has the potential to accumulate in the environment.
  • It is best to reduce sugar intake without relying on artificial sweeteners. Therefore opt for protein and healthy fats with wholegrain or vegetable sources of carbohydrate to stabilise blood sugar levels and help to reduce sugar cravings.
  • If sweetness is needed, opt for foods with natural sweetness such as honey, tropical fruit or dried fruit. Or 70% dark chocolate is a good choice.

If you have any questions regarding the topics that have been raised, or any other health matters please do contact me (Helen) by phone or email at any time., 01684 310099

Helen Drake and the Cytoplan Editorial Team

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  1. American Dietetic Association. Position of the American Dietetic Association: Use of Nutritive and Nonnutritive Sweeteners. J Am Diet Assoc. 2004;104(2):255-275. doi:10.1016/j.jada.2003.12.001
  2. Chattopadhyay S, Raychaudhuri U, Chakraborty R. Artificial sweeteners – a review. J Food Sci Technol. 2014;51(4):611-621. doi:10.1007/s13197-011-0571-1
  3. Suez J, Korem T, Zilberman-Schapira G, Segal E, Elinav E. Non-caloric artificial sweeteners and the microbiome: findings and challenges. Gut Microbes. 2015;6(2):149-155. doi:10.1080/19490976.2015.1017700
  4. Swithers SE. Artificial sweeteners are not the answer to childhood obesity. Appetite. 2015;93:85-90. doi:10.1016/j.appet.2015.03.027
  5. Swithers SE. Not so Sweet Revenge: Unanticipated Consequences of High-Intensity Sweeteners. Behav Anal. 2015;38(1):1-17. doi:10.1007/s40614-015-0028-3
  6. Pepino MY. Metabolic effects of non-nutritive sweeteners. Physiol Behav. 2015;152(Pt B):450-455. doi:10.1016/j.physbeh.2015.06.024
  7. Swithers SE, Laboy AF, Clark K, Cooper S, Davidson TL. Experience with the high-intensity sweetener saccharin impairs glucose homeostasis and GLP-1 release in rats. Behav Brain Res. 2012;233(1):1-14. doi:10.1016/j.bbr.2012.04.024
  8. Deniņa I, Semjonovs P, Fomina A, Treimane R, Linde R. The influence of stevia glycosides on the growth of Lactobacillus reuteri strains. Lett Appl Microbiol. 2014;58(3):278-284. doi:10.1111/lam.12187
  9. Suez J, Korem T, Zeevi D, et al. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 2014;514(7521):181-186. doi:10.1038/nature13793
  10. Iyyaswamy A, Rathinasamy S. Effect of chronic exposure to aspartame on oxidative stress in the brain of albino rats. J Biosci. 2012;37(4):679-688. Accessed October 1, 2018.
  11. Ashok I, Sheeladevi R. Biochemical responses and mitochondrial mediated activation of apoptosis on long-term effect of aspartame in rat brain. Redox Biol. 2014;2:820-831. doi:10.1016/J.REDOX.2014.04.011
  12. Abhilash M, Alex M, Mathews V V., Nair RH. Chronic Effect of Aspartame on Ionic Homeostasis and Monoamine Neurotransmitters in the Rat Brain. Int J Toxicol. 2014;33(4):332-341. doi:10.1177/1091581814537087
  13. Maher TJ, Wurtman RJ. Possible neurologic effects of aspartame, a widely used food additive. Environ Health Perspect. 1987;75:53-57. doi:10.1289/ehp.877553
  14. Sharma VK, Oturan M, Kim H. Oxidation of artificial sweetener sucralose by advanced oxidation processes: a review. Environ Sci Pollut Res. 2014;21(14):8525-8533. doi:10.1007/s11356-014-2786-y
  15. Erbaş O, Erdoğan MA, Khalilnezhad A, et al. Evaluation of long-term effects of artificial sweeteners on rat brain: a biochemical, behavioral, and histological study. J Biochem Mol Toxicol. 2018;32(6):e22053. doi:10.1002/jbt.22053

Last updated on 20th November 2020 by cytoffice


15 thoughts on “The truth behind artificial sweeteners

  1. Your Blogs are very informative and where possible we try eat fresh
    and non prepared food when ever we can . We keep sugar to a minimum and is used in cake baking only , certainly not in drinks .

  2. Artificial is just that. It is not an alternative to sugar. Sugar is highly acidic on the body and can cause damage to the gut wall. If looking for alternatives then honey or maple syrup is probably best but bearing in mind food miles then honey be would be preferable in small amounts. It’s also a simple switch to baking and cooking with honey. And if you care about the environment consider signing up with your local beekeepers group.

  3. I’ve been trying for years to get my daughters-in-law/ friends to give up artificial sweeteners but they just won’t listen despite being quite intelligent people. As soon as the government brought out the sugar tax I took to screaming at the TV screen that instead of helping the population they were condemning them to eat poison instead. I feel like taking a spray paint can to supermarkets & spraying the word poison all over the soft drinks aisles. I went crazy trying to find a soft drink mixer that didn’t contain this poison until I discovered Fever Tree. Hooray I can now enjoy a tonic with an occasional gin. Rant over. Can we start a petition to get companies to change to something better? It’s Halloween tonight & I made sure that all the treats I’m handing out only contain good stuff.

    1. Hi Janet,

      Thank you for your question on our blog.
      There have been mixed results on the effects of stevia on the gut microbiota – in one study it did have an effect on levels of Lactobacillus reuterii but at the current time it seems that any effects may be small. More research is needed. If you are using stevia in hot drinks then it would be a good idea to consider how much you are using and limit consumption by reducing the amount you add. Also at some times of day you may be able to have an alternative drink that does not need sweetening e.g. herbal or fruit tea. So perhaps use as little as possible.

      Best wishes,

      1. Thanks Clare, I have stopped using stevia in my coffee, instead I’m putting just a quarter of a spoon of sugar in instead. Thank you for your helpful reply. ….Kind regards…Janet.

  4. Interesting article, thank you. Did your research cover anything about coconut sugar? Maybe this is a gut-friendly option?

    1. Hi Elisabeth,

      Thank you for your comment. Yes coconut sugar is a good choice of natural sweetener (as are good quality honey and maple syrup). Obviously all these are best used in small amounts as an occasional treat as they are still forms of sugar. Our hunter-gatherer ancestors probably ate 1 to 2 kg of sugar per year if they were lucky enough to find honey.


  5. Thank you for this article. I have always avoided artificial sweeteners, believing that it’s best to educate the palate towards less sweetness. It is good to understand the reasons for not accepting these sugar substitutes, which so many people think are magic

  6. Excellent, thorough and referenced article.

    Finding soft drinks (eg squash) without AS is problematic and requires reading tiny print on labels. AS-laden drinks are now the normal.

    Shocking that AS-laden foods and drinks have been freely sold in NHS hospital shops.

  7. Interesting article, but it doesn’t appear to be a comprehensive article, including all AS’s. Mannitol was not included. The small amount of research I have read on mannitol, is that it can actual feed some healthy gut bacteria. While I agree that AS’s are not entirely healthy, neither is sugar. Food choices are always about balancing many factors against risks and gains. I personally find sweet foods (especially sugar) incredibly addictive; it seems to throw a switch, making me crave more. I find abstinence works best for me and choose to abstain most of the time for health reasons. However, our western food environment is piled so high with sugary foods everywhere, that they are hard to avoid. Where I can I choose the AS options, as they don’t seem to flip the switch!

    1. Hi Sven – Thank you for the evidence for mannitol as a prebiotic is quite weak but I appreciate that it may be having some benefit in the gut. A 2019 review says: “Mannitol (E-421) is an isomer of sorbitol and is obtained from the hydrogenation of glucose and its consequent purification. Although less sweet than sorbitol, mannitol is also used in food because it has a high metabolization ratio (the ratio of a drug metabolite concentration to its parent drug concentration, expressed as a range) of ∼75%; the other 25% is absorbed before being excreted in the urine. Because it is virtually inert (i.e., it does not react with active components of drugs) and confers a cool sweet taste, apart from being used in the food industry it is also widely used in dental hygiene products, drug fillers, and as a diuretic in intravenous fluids (5, 17, 31, 94, 95). To our knowledge, no data on the effects of mannitol on the gut microbiota are available.”

      The only information I have seen on this is from probiotic companies but I cannot find the research linking to it, therefore it is likely it has been done in-house. Additionally however, there is still an issue with artificial sweeteners disrupting normal satiety mechanisms and increasing calories intake and sugar cravings. They can certainly be useful for some people who need to reduce calorie intake but have a reliance on sugar, however we are presenting current evidence as much as we can (this article is over a year old) so you can make an informed decision. Personally I would use foods that are naturally sweet over any artificial sweetener but you do need to work specifically with individuals as to what works for them. As always it is assessing the needs and benefits of every person.


  8. Your articles are always informative thank you. I eat very little sugar and eat a low carb diet but want to make some chutney and pickles from home produce. They require some sugar. I was going to use xylitol as I believe it doesn’t affect blood sugar levels..but maybe I should use coconut sugar instead? Usually I ferment stuff but fancied some chutney as a treat.

    1. Hi Bev,

      Thank you for your comment. Xylitol doesn’t affect blood sugar levels directly but it does (as anything which tastes sweet but has no calories) interfere with insulin signalling, as well as signalling satiety hormones can in the long run be unhelpful. I would recommend using smaller amounts of naturally sweet foods to help with sugar cravings but at the end of the day reducing sweet foods is the best option. Coconut sugar can be used in moderation.


  9. I have been relentless in my campaign against artificial sweetners for over 30 years…’s been a hard slog! I am over the moon and dancing in my garden to read your article, thank you thank you! It is an excellent article <3

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