Artificial sweeteners: good or bad?

Amy Wood - Nutritionist

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We all know that too much free sugar in our diets isn't healthy, but it can be difficult to avoid, especially if you have a sweet tooth and enjoy sugary treats! Enter sweeteners: these sugar substitutes have increased massively in popularity, especially among those on a mission to lose weight. However concerns have been raised over the years regarding the safety of their use, alleging they may increase the risk of diseases such as cancer. So we've taken a look at the evidence to see what the truth is about the link between sweeteners and health.

What are artificial sweeteners?

Artificial sweeteners are non-natural compounds added to foods and beverages to make them taste sweeter. They are often much more sweet than sugar (up to several thousand times more), meaning only a tiny amount is needed to achieve the same flavour intensity. They also tend to be lower in calories, with many sweeteners classed as 'zero calorie' as our bodies are unable to break them down and use them for energy. This makes them a popular choice for weight loss, as they provide the same sweet taste as sugar without the empty calories.

You may be familiar with brands like Splenda, Canderel, Sweetex, Sweet'N Low and Truvia. These are tabletop sweeteners, sold in either powder or tablet form, for consumers to use at home in beverages and baking. Artificial sweeteners are also used in food manufacturing, added to thousands of different products including sugar-free drinks, baked goods, desserts, sweets, dairy products, snacks, ready meals, and chewing gum. They form the basis of sugar-free sauces and syrups too.

Sweeteners approved for use in the UK include:

  • Acesulfame K (200 times sweeter than sugar)
  • Aspartame (200 times sweeter than sugar)
  • Saccharin (300 times sweeter than sugar)
  • Sorbitol (half as sweet as sugar)
  • Stevia (200-350 times sweeter than sugar)
  • Sucralose (600 times sweeter than sugar)
  • Xylitol (the same sweetness as sugar)

Do artificial sweeteners cause cancer?

The artificial sweeteners debate tracks as far back as 1970. An animal study published that year found that feeding rats extremely high doses of saccharin over 2 years increased their risk of bladder cancer [1]. This caused quite a stir within the health and wellness sector, with many consumers steering clear of sweeteners under the impression they would cause cancer in humans too.

The way foods behave within rodents' bodies doesn't necessarily reflect the effect they might have on humans, meaning we can’t accurately predict how artificial sweeteners behave in us based on animal studies alone. As a consequence, observational research has been undertaken to study the effects of artificial sweeteners in humans. One very recent study did report a link between sweetener intake and cancer risk, suggesting that people who ate sweeteners, especially aspartame and acesulfame-K, had a 12-15% increased risk of overall cancer risk than those who didn’t [2]. This was a very large study on a cohort of over 100,000 people, however the study didn’t compare with the effects of sugar intake on cancer risk, which is often what sweeteners are used to replace.

Aside from this study, the majority of studies and reviews up until now have found no such link [3, 4, 5, 6]. Both Cancer Research UK and the American National Cancer Institute have stated that artificial sweeteners do not cause cancer in humans [7, 8].

What about weight gain?

Although most artificial sweeteners are zero-calorie, some questions are still circulating as to the real benefit of sweeteners over sugar in health and weight loss.

A common concern is the effect of sweeteners on appetite and weight gain. It's thought their sweet flavour fires off the same reward centres of the brain as sugar, meaning we get the same happy feeling as we do with the real deal. However feeding these pleasure centres means we develop further cravings for sweet foods, especially considering the body doesn't get the actual energy it expects when tasting sweet food. The more sweet flavours we taste, the higher our tolerance for sweetness becomes. This has been shown to increase our intake of sugar and calories overall [10]. One study found that the sweetener sucralose actually elicited a stronger increase in appetite than sugar, particularly in women and those classed as obese [11], although this may not necessarily create weight gain according to a recent review [12].

Do artificial sweeteners impact other areas of our health?

The same study that explored cancer risk with artificial sweetener consumption also investigated the effect on heart health, which is a concern for many of us, particularly with excess weight and in later life. They identified a 9% increased risk of cardiovascular disease with consumption of sweeteners, including a 40% increased risk of coronary heart disease with acesulfame K. [13]. This may seem like a shocking stat, however it’s important to remember observational studies like this can only show us a link – more research is needed to understand the relationship between sweeteners and cardiovascular health. It’s also worth noting that the subgroup of participants with the greatest sweetener intake were also the biggest consumers of sugar-sweetened beverages, which has been historically linked with cardiovascular disease risk too.

It's been suggested that artificial sweeteners may disrupt gut bacteria [14]. Our gut is central to our overall health, with poor gut health being associated with a weakened immune system, irritable bowel syndrome and difficulty regulating blood glucose, meaning some studies have even found a link to type 2 diabetes [15]. A chronic imbalance in the gut microbiome has also been associated with obesity [16], so it may be especially important to prioritise a healthy gut if you're concerned about your weight. A study published in 2022 looked at the impact of sweeteners on blood sugar control when dosed with sugar. Researchers found that saccharin and sucralose in particular impaired blood sugar response. They then transferred gut bacteria from participants to mice and looked at their response to the sweeteners, and the same thing happened! This suggests our gut microbiome might be involved, and that different sweeteners may produce individualised effects on the gut. [17]. Several other studies have identified a link between artificial sweetener intake and poor gut bacteria [18, 19], however ultimately, more research is needed to establish the true effect of artificial sweeteners on gut microbiota.

The findings above regarding glucose control may be ringing alarm bells regarding type-2 diabetes. There isn’t currently enough strong evidence to suggest that artificial sweeteners increase our risk of developing type-2 diabetes, and may still have a lesser effect on blood glucose response than excess sugar intake.

Sweetener in tea

How much is too much?

The European Food Safety Authority (EFSA) has rigorous regulations in place to ensure a safe intake of artificial sweeteners. The Acceptable Daily Intake (ADI) is the figure used to represent a safe daily intake over a lifetime and is based on the body weight of each person. Each type of artificial sweetener goes through rigorous testing and research commissioned by EFSA, and the evidence is constantly being re-evaluated. The acceptable daily intake levels are often set much higher than would be reasonably possible for most humans to consume for safety reasons. For example, the ADI for sucralose is set at 15mg per kilogram of body weight per day [20]. For a 70kg person, this would be 1050mg per day – the equivalent to 83 sachets of Splenda!

Should I include them in my diet?

Artificial sweeteners represent a zero-calorie alternative to sugar, which we know is linked with obesity and poor dental health when eaten in excess. In fact, some sweeteners, like xylitol, may actually have protective effects in reducing tooth decay [21]. The use of artificial sweeteners may be especially useful for anyone looking to reduce their sugar consumption, including those of us on a weight loss journey or those living with type-2 diabetes.

That said, as evidence continues to emerge that may bring the long-term safety of artificial sweeteners into question, the ultimate goal is for us to adapt our diets to reduce the overall level of sweetness we are used to. By keeping an eye on both sugar and sweeteners, we may be able to 'train' our palate to be satisfied by a lower level of sweetness. As opposed to a direct replacement, sweeteners may be suitable for short-term use as a ‘steppingstone’ to reducing sweetness tolerance. This can help nudge us away from processed products that contain sugars and sweeteners and towards a diet rich in whole, unprocessed foods.

Of course, there’s no denying most of us enjoy sweet foods, and cutting them out completely is both unrealistic and unenjoyable! For the time being, occasionally popping a Splenda in your tea instead of sugar or switching your cola for a diet version are safe swaps to make to save on empty calories and free sugar intake. Scientific opinion is constantly being updated as new research emerges.

Nutritionist Amy Wood (ANutr), MSci BSc Nutrition has a keen interest in the relationship between diet and health. Having been published in the European Journal of Nutrition, Amy is passionate about making evidence-based nutrition accessible to everyone and helping others to adopt a food-focused approach to taking control of their health.

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