Getting the Facts Straight // Artificial Sweeteners + Other Sugar Substitutes
Artificial sweeteners are often a topic of rather heated discussion. Some claim that they increase your risk of cancer and negatively affect blood sugar levels, whilst most health authorities deem them safe for consumption and encourage their use in food products over sugar. But what are sweeteners and how do they differ from sugar? How are they processed by the body? Do any of them convey any health benefits? Hopefully, by the time you get to this post, you’ll have answers to all of these questions.
What are artificial sweeteners?
Sugars are all composed of the same monosaccharide ‘building blocks’ - glucose, fructose, and galactose (pictured below) - that make them sweet. As you can see from the structures below, monosaccharides all have a very similar chemical structure, just with different linkages of carbon chains and slightly altered configurations. Disaccharide sugars are just made up of two of these molecules, for example maltose is made up of 2 glucose molecules, sucrose is composed of a fructose and glucose molecule joined together, and lactose is made up of glucose and galactose.
Monosaccharide and disaccharide
Unlike sugars, artificial sweeteners come in all shapes and sizes. Some have more simple structures, whilst others are more complex. Below you will see some of the examples of artificial sweeteners and sugar substitutes that I'll be discussing in this post. Sucralose looks a lot like sucrose, with the substitution of some -Cl and -CH2OH groups, however the others don't look like sugar at all. Just as as differ greatly in their structure, they also don't act in the same way when we consume them.
Commonly consumed artificial sweeteners
and sugar alternatives
Types of artificial sweeteners and sugar alternatives
Aspartame is an interesting artificial sweetener because it’s actually made up of two amino acids, which are the ‘building blocks’ of protein. These amino acids – aspartic acid and phenylalanine – are joined together, and are really good at tricking your taste buds into believing that they are sweet. In fact, aspartame tastes about 200 times sweeter than sugar. When consumed, aspartame is broken down into its by-products – phenylalanine, aspartic acid, and small amounts of methanol – which are absorbed and metabolised by the body as amino acids and alcohols would normally be. Aspartame produces about 4kcal/g when metabolised (its components are protein ‘building blocks’ after all) and thus is not technically a ‘zero calorie’ sweetener, however, it is consumed in such small amounts that it has a relatively little impact on the caloric intake when eaten. Aspartame is probably one of the most widely debated sweeteners out there, however despite the controversy it has been fairly rigorously tested for safety and is considered safe at normal levels of human consumption (acceptable intake: 40mg/kg body weight) . Just a really important note here that aspartame is not safe for those who suffer from PKU (phenylketonuria) can’t metabolise phenylalanine, and should thus avoid aspartame.
2. Acesulfame K
This ‘zero calorie’ sweetener is up to 200 times sweeter than sugar, much the same as aspartame. It is not digested or stored in the body when consumed but is actually absorbed and excreted in its unchanged form. Critics of this sweetener argue that acesulfame K is harmful, causing cancer, affecting pregnancy, and causing tumours, however, most food safety authorities have dismissed these claims due to the poor quality of research supporting these claims . Acesulfame K has been shown to negatively affect the gut microbiome and cause weight gain in mice, however, this evidence can’t be directly translated to humans and more rigorous research is needed to properly determine the effects of the sweetener on our gut bugs . Once again, this sweetener is approved for use in foods as its consumption at normal levels as is not known to cause harm in humans (acceptable intake: 9mg/kg body weight).
This sweetener packs quite the punch - it’s up to 1000 times sweeter than sucrose! Unlike other sugar alternatives, this sweetener looks a bit like sucrose, however, the differences in its chemical structure mean that most sucralose consumed cannot be absorbed by the body. Only about 8-20% enters the bloodstream, but it isn’t metabolised at all and is excreted fairly quickly through urine, which makes it a ‘zero calorie’ sweetener. There is lots of good research to show that when consumed in normal amounts, sucralose is safe to eat and is unlikely to lead to accumulation or negative effects in the body .
Despite being marketed as a ‘natural sweetener’, Stevia still undergoes significant processing to get it into the form that we can purchase from the shops. It is extracted from the leaves of the plant Stevia rebaudiana through the processes of drying, extraction, separation, and crystallisation using solvents (not quite as ‘natural’ as a lot of food packaging often makes out to be, is it?). Anyway, that’s not to say that it’s not safe or useful to use in food products. The World Health Organization has determined that it is safe for consumption at normal levels of exposure (acceptable intake: 4mg/kg body weight). Stevia is a useful ‘zero calorie’ sweetener and can be used in very small amounts due to the fact that it is made up of Steviol glycosides, which are up to 150 times sweeter than sucrose. There is a really great review of Stevia here if you would some more detailed information about this sugar alternative .
5. Sugar alcohols / polyols
Xylitol, erythritol, maltitol, and sorbitol are all examples of sugar alcohols. These are an interesting alternative to sugar that can be used in foods as well as things like toothpaste and chewing gum. They’re not quite as sweet as sugar, with ±60% of sugar’s sweetness, and provide 2.6kcal/g when consumed. Unlike a lot of other sweeteners, polyols have virtually no aftertaste and can be used almost 1:1 in baking due to their chemical structure. Here’s the thing though – when ingested, these sweeteners are essentially slowly and only partly absorbed in the intestine. The molecules that are absorbed end up being transported to the liver where they are converted into fructose for the body to use. However, the fact that polyols are not absorbed completely means that choosing to replace sugar with polyols can lead to water being drawn into the colon. For those that are sensitive to polyols (like many IBS sufferers), this can cause water retention, diarrhoea, bloating and gas, as unabsorbed polyols are broken down into carbon dioxide before being eliminated . This is why food products containing sugar alcohols generally carry a warning that reads something along the lines of ‘May have a laxative effect’. They're not all bad news though, in fact polyols are known to promote dental health by helping to neutralise plaque acidity on teeth and support the repair of tooth enamel [6, 7], and they have a smaller effect on blood glucose than sugar, and are thus useful for stabilising and controlling blood sugar levels.
Cyclamate is around 30-50 times sweeter than sugar, making it one of the less potent sugar alternatives. It is often used in conjunction with other sweeteners, such as saccharin (described below), to ensure a favourable taste profile in food products. In 1970, a study found that cyclamate was associated with bladder cancer in rats, which resulted in it being banned in the USA [8, 9]. Other animal-based studies involving the feeding of large quantities of cyclamate to animals for a period of years, were conducted in the years that followed that showed similar results [8, 9]. It has been suggested that this carcinogenicity is related to the fact that cyclamate is converted to a more toxic metabolite, cyclohexamine, but gut microorganisms when consumed .
This is actually the first artificial sweetener to be produced. Originally, saccharin was produced and used during World Wars I and II due to its low production costs compared with sugar. It was only in the 1950s, with the rise of fat-free and diet foods, that saccharin started being used for the purpose of reducing the number of calories in food products. Saccharin is a non-nutritive sweetener that is about 300-400 times sweeter than sugar. Like a number of the other 'zero calorie' sweeteners already mentioned, we can't metabolise it so it passes through the body unchanged when consumed. It is often mixed with other sweeteners (like aspartame and sodium cyclamate, already discussed) due to its bitter aftertaste. Saccharin is heat stable and chemically inert and is thus rather popular with the food industry (good shelf-life stability is always a bonus for food producers). What about its safety? Back in the 1970s, there were a number of studies performed in laboratory rats that involved feeding them high doses of the sweetener for a period of months to years. Some of these studies found that saccharin was associated with the development of bladder cancer in these rats , BUT there are a few things that must be noted and acknowledged here. Firstly, these studies were performed in rats (animal studies cannot be directly translated to humans), and secondly, they were fed daily amounts of saccharin that far outweigh what we as humans would ever regularly consume (some involved feeding the rats a high concentration of up to 5% saccharin in their diet). Furthermore, large epidemiological studies conducted in more recent years have shown no evidence that saccharin is associated with bladder cancer in humans  and they are thus considered safe for consumption in humans in normal quantities (acceptable intake: 5 mg/kg body weight) [10, 11].
How are sweeteners produced?
I think I might bore you if I go into too much detail here regarding how each of these sweeteners are manufactured, so instead, I thought I would put together a list of good resources for those who want to know more about the processes, just click through to the links below. You can also find brief information for most of the sweeteners listed above in this review article. It’s actually all rather fascinating.
What do we know about these sugar substitutes?
They are generally regarded as safe for consumption by humans
Unlike sugar, they don’t increase the risk of dental cavities and tooth decay
They do not raise blood sugar in the same way that sugar does and are thus thought to not contribute to Type 2 diabetes risk (BUT this is still not certain due to lack of rigorous research, as you will see below) [12, 13]
They don’t always taste great and can have a bitter aftertaste
They do not have a huge impact on body weight
Most can’t be substituted 1:1 for sugar in baking as they have very different chemical structures
They do not convey any known health benefits, apart from polyols used in chewing gum and toothpaste, which have been shown to benefit oral hygiene
What don’t we know about them?
We also don’t know the long-term cardiometabolic and other health effects of artificial sweetener consumption. They could actually be associated with an increased risk of long-term weight gain, diabetes, and high blood pressure, rather than being a better choice than normal sugar 
My (current) opinion
Our bodies are equipped to handle sugar in the diet in moderate amounts, so there is no need to substitute regular sugar if you tend to eat small amounts of it anyway.
I don’t like the taste of most artificial sweeteners, and I find that I can definitely taste their bitter aftertaste (sucralose is probably the one I hate the most)
Sugar alcohols give me a very upset tummy. This is probably why I struggle to understand how people can use things like xylitol and erythritol in all of their baking. I suppose some of us are more sensitive to them than others, but I have come to realise that I suffered from my worst GI symptoms when I replaced sugar in my tea and coffee with xylitol a few years ago. This is definitely something you should think about if you tend to have an upset tummy.
The use of approved artificial sweeteners and sugar alternatives shouldn't be harmful to us in the quantities we would normally consume them, however, we do not know their long-term effects on things like diabetes risk, energy intake, and our gut microbiome.
If you tend to enjoy multiple cups of sweet tea/coffee each day, perhaps using a sweetener is a good way to reduce sugar intake whilst still being able to enjoy your sweet hot drinks. However, there is evidence to suggest that because sweeteners provide a sweet taste without providing any energy, they may end up increasing cravings for sweet foods anyway.
If you want to use artificial sweeteners and sugar alternatives in place of sugar, then go for it. But if you don't want to, don't sweat it. That's perfectly OK.
 FDA Food Standards Agency. Food additives [Internet]. 2018 Jan 9 [cited 2018 Aug 26]. Available from: https://www.food.gov.uk/safety-hygiene/food-additives
 West, H. What is acesulfame potassium, and is it good or bad for you? [Internet]. Medical News Today. 2017 Aug 1 [cited 2018 Aug 26]. Available from: https://www.medicalnewstoday.com/articles/318604.php
 Bian X, Chi L, Gao B, Tu P, Ru H, Lu K. The artificial sweetener acesulfame potassium affects the gut microbiome and body weight gain in CD-1 mice. PLOS ONE. 2017 Jun 8;12(6):e0178426. Available from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0178426
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 Holgerson PL. Xylitol and its effect on oral ecology– clinical studies in children and adolescents [dissertation]. Umeå, Sweden:Umeå University; 2007. 60 p. Available from: http://www.diva-portal.org/smash/get/diva2:145297/FULLTEXT01.pdf
 EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the substantiation of health claims related to the sugar replacers xylitol, sorbitol, mannitol, maltitol, lactitol, isomalt, erythritol, D‐tagatose, isomaltulose, sucralose and polydextrose and maintenance of tooth mineralisation by decreasing tooth demineralisation (ID 463, 464, 563, 618, 647, 1182, 1591, 2907, 2921, 4300), and reduction of post‐prandial glycaemic responses (ID 617, 619, 669, 1590, 1762, 2903, 2908, 2920) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal. 2011 Apr;9(4):2076 (25 pp.). Available from: https://efsa.onlinelibrary.wiley.com/doi/abs/10.2903/j.efsa.2011.2076
 Takayama S, Renwick AG, Johansson SL, Thorgeirsson UP, Tsutsumi M, Dalgard DW, Sieber SM. Long-Term Toxicity and Carcinogenicity Study of Cyclamate in Nonhuman Primates. Toxicol Sci. 2000 Jan;53(1):33-9. Available from: https://academic.oup.com/toxsci/article/53/1/33/1673343
 Weihrauch MR, Diehl V. Artificial sweeteners—do they bear a carcinogenic risk? Ann Oncol. 2004 Oct;15(10):1460-5. Available from: https://academic.oup.com/annonc/article/15/10/1460/170200
 Touyz LZG. Saccharin deemed "not hazardous" in United States and abroad. Curr Oncol. 2011 Oct;18(5):213-4. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3185898/
 Brown MJ. Saccharin - Is This Sweetener Good or Bad? [Internet]. Healthline. 2016 Jul 9 [cited 2018 Aug 26]. Available from: https://www.healthline.com/nutrition/saccharin-good-or-bad#section3
 Azad MB, Abou-Setta AM, Chauhan BF, Rabbani R, Lys J, Copstein L, Mann A, Jeyaraman MM, Reid AE, Fiander M, MacKey DS, McGavock J, Wicklow B, Zarychanski R. Nonnutritive sweeteners and cardiometabolic health: a systematic review and meta-analysis of randomized controlled trials and prospective cohort studies. CMAJ. 2017 Jul;189(28):E929-E939. Available from: http://www.cmaj.ca/content/189/28/E929
 West H. Do Artificial Sweeteners Harm Your Gut Bacteria? [Internet]. Healthline. 2017 Sep 13 [cited 2018 Aug 26]. Available from: https://www.healthline.com/nutrition/artificial-sweeteners-and-gut-bacteria
 Curi R, Alvarez M, Bazotte RB, Botion LM, Godoy JL, Bracht A. Effect of Stevia rebaudiana on glucose tolerance in normal adult humans. Braz J Med Biol Res. 1986;19(6):771-4. Available from: https://www.ncbi.nlm.nih.gov/pubmed/3651629