Why we’re not sweet on Sucralose – the bitter truth about artificial sweeteners

The quantity of artificial sweeteners we consume in our diets has increased dramatically over recent years – and it’s no wonder. With food manufacturers looking to showcase the newest and best “low-calorie” and “sugar-free” foods to appeal to the growing and competitive health food scene and diet culture, the tendency to rely on artificial sweeteners to meet this demand has become the norm.

Artificial sweeteners are synthetic chemicals that mimic the sweetness of sugar, without any added calories1. By using artificial sweeteners, we can add more and more sweetness to our foods and beverages – without adding any calories or carbohydrates to our intake. For those of us watching our weight, cutting back on sugar or watching our blood sugar levels, this appears to be nothing short of a diet breakthrough and a perceivably healthy strategy in replacing sugar and easing our cravings, and due to a successful marketing effort by many popular products such as Diet Coke, the weight conscious public often consider artificial sweeteners as “health food”.

This perception has encouraged the overuse and reliance on sweeteners as a “healthy alternative” to sugar and a suitable strategy to avoid putting on weight – an alarming trend considering the growing research that shows that even when consumed in moderation, these additives are in fact doing no favours for our wellbeing – let alone our waistline.

Sucralose: the worst offender

Sucralose was first discovered in 1976 and is now one of the most commonly used artificial sweeteners and sugar substitutes. It is known as a “non-nutritive sweetener” – being up to 650 times sweeter than sugar1 yet without any caloric value. The substance has been used as a sugar substitute in a wide variety of products – these include diet drinks, low-fat yoghurts, baking mixes, protein powders, table-top sweeteners (such as Splenda), chewing gum and even in breakfast cereals and salad dressings (see Figure 1).

Figure 1: The foods that are commonly packed with artificial sweeteners like sucralose.


Sucralose has always been considered ‘safe’ for human consumption because initial research found it to be biologically inert – meaning that it passes through the human body untouched 2. The substance has been deceptively marketed as a more ‘natural’, and ‘safer’ sweetener ever since.

This is despite several large-scale studies over the past 30 years displaying positive correlations between artificial sweetener use and interactions with the body, e.g. increased weight gain and metabolic dysfunction. Indeed, research has shown numerous times that the sweetener is not entirely inert, and can in fact interact with the body in a myriad of ways – even when consumed in small doses.

The most recent and alarming research comes from a study analysing the effects of sucralose on stem cells derived from human fat tissue 3. In their studies, the researchers discovered that consumption of this sugar substitute plays havoc with the body’s metabolism by altering glucose and insulin levels – and in doing so, may even promote the accumulation of fat.

Sweet but not satisfying

To put the science simply, when you consume sweet-tasting but non-caloric or reduced-calorie food and beverages, you may essentially be interfering with learned responses by the body in response to increased sugar or energy intake. Indeed, the human brain may respond to sweetness in two ways; by releasing more glucose into the body, and by priming signals to eat more.

Physiologically, when we consume artificial sweeteners and give our bodies a sweet taste without any calories, we can essentially stimulate the same receptors in the body that react to sugar by increasing transport of glucose into cells. As the body absorbs this glucose, our blood sugar levels rise, and as our blood sugar levels rise, our body releases insulin, which promotes the blood sugar to leave the blood and enter our cells – where it will either be used for energy or stored as fat.

At the same time, the sweeteners may be tapping into our hedonic reward-system for sweet tasting foods, stimulating receptors in a way that encourages cravings for sweets and enhances hunger signals. When we ingest artificial sweeteners, we are tantilising the reward system in our brain integrated with receiving a ‘reward’ in the form of energy (calories). However, because the sweeteners do not contain any caloric value, they fail to activate a post-ingestive component of satiety – meaning that despite their marketed intention of “satisfying our sugar cravings”, sweeteners really only manage to tickle our taste buds, not satisfy us. In fact, all they may be doing is creating an imbalance between sweetness versus energy – a discrepancy which the brain recalibrates by fueling further food seeking behavior and calorie consumption to achieve a real “reward” or satiation4.

As you can see, both these processes, over time, could lead to an increase appetite, increased food intake and abdominal fat storage– meaning that counterintuitively, frequent consumption of ‘diet’ options in replacement of sugar may actually induce weight gain and obesity!

Sweeteners and our gut

Another route through which artificial sweeteners like sucralose may disrupt our metabolic processes is by dramatically changing the population of our gut microorganisms. Research has found that adding sucralose to the drinking water of mice increases their blood sugar levels higher than those of mice who drank sugar water, and that certain types of gut microbes were more common in these mice fed sucralose. The researchers suggested that ingestion of sucralose enhanced the growth of these bacteria, and that molecules then produced by these bacteria worked to increase glucose production in the body and push blood glucose levels out of balance – favouring the extraction of energy from food and conversion of that energy into fat. While there is a lot more research needed, the conclusion from the study was that sweeteners are in fact capable of altering gut microbial composition and function, in turn disrupting metabolic process in ways that favour fat accumulation.5

The most recent study on the effects of chemical sweeteners on humans was undertaken thanks to Michael Moore’s ‘Trust Me I’m A Doctor’ program, carried out by Dr James Brown at Aston University. Following the report from a small study in 2014 which had shown that artificial sweeteners had disrupted the gut bacteria of mice, and when they tested saccharin on 7 people they found that it did the same to 4 of them, as well as making their blood sugar levels less healthy, they decided to do their own test.

They tested groups on artificial sweeteners vs the natural sweetener stevia – and the effects were astounding. The blood sugar levels of the volunteers taking stevia had not changed significantly. However, 4 of those who had taken saccharin had significantly higher blood sugar levels – meaning that the average of the group was overall significantly higher.

This raised blood sugar level is bad for their health, and means that in fact the saccharin, in a large proportion of people, is doing the opposite of what it promises. Far from protecting them from the bad effects of sugar, it is raising their blood sugar levels itself.

The results of the gut bacteria tests, analysed by Dr Paul Cotter of the Teagasc Food research institute, showed that those people who reacted to saccharin all had a similar bacterial composition to start with, and that they all changed in a similar way.

Meanwhile those who didn’t respond to the saccharin showed much less of a change.

Those taking stevia did see a bacterial change, but it was in the opposite direction from those who had a bad response to saccharin. Read the full study here.

Take home message

So while we’ve been reaching for the “healthy alternative”, “diet”, “sugar-free” and “low-calorie” foods packed full of artificial sweeteners all these years in a bid to lose weight or avoid sugar-induced health afflictions…we may have actually been setting ourselves up for the very ailments they we thought we were fighting. Scary, right?!

Indeed, with all this research coming to light, it’s becoming pretty apparent that the world of “diet foods” needs a major re-thinking and that us consumers should adopt a precautionary principle when consuming artificial sweeteners like Sucralose – despite the fact that they continue to be recommended and promoted as healthy sugar substitutes. If you’re like us, this research has made us realise that a quick sweet hit from our Coke Zero or ‘no-added sugar’ snacks are just not worth the accumulative digestive and metabolic issues that come with it.

And, of course, the negative consequences of artificial sweeteners that we have shed light on here should not be interpreted as a suggestion that we should all go back to sugar instead! For optimal health, we recommended cutting down on both, and making a conscious effort to stick to products that contain only natural sweeteners e.g. Stevia, xylitol and erythritol.


  1. Chattopadhyay S, Raychaudhuri U, Chakraborty R. Artificial sweeteners – a review. Journal of Food Science and Technology. 2014;51(4):611-621.
  2. http://www.medicalnewstoday.com/articles/262475.php
  3. Swithers, S.E. Artificial sweeteners produce the counterintuitive effect of inducing metabolic derrangements. Trends in Endocrinology & Metabolism. 2013; 24(9). 431-331
  4. Yang Q. Gain weight by “going diet?” Artificial sweeteners and the neurobiology of sugar cravings: Neuroscience 2010. The Yale Journal of Biology and Medicine. 2010;83(2):101-108.
  5. http://www.sciencemag.org/news/2014/09/artificial-sweeteners-may-contribute-diabetes-controversial-study-finds

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