Artificial sweeteners: good or bad?

Amy Wood - Nutritionist | 28 May, 2022

We all know that too much free sugar in our diets isn't healthy, but it can be difficult to avoid sweet treats, especially if you have a sweet tooth! Enter sweeteners. These sugar substitutes have increased massively in popularity, especially among those of us 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 sweeter 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)

Why are we worried about them?

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 it would cause cancer in humans too. It's important to note that the way foods behave in rodents doesn't necessarily reflect the effects on humans, meaning we can’t accurately predict how artificial sweeteners behave in humans based on animal studies alone.

What the current science really tells us

1. Safety

In the wake of these animal studies, much observational research has been undertaken studying the effects of artificial sweeteners in humans. Although one very recent study did report a link between sweetener intake and cancer risk [2], the majority of studies and reviews 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].

Of course, we can all have too much of anything. That's why the European Food Safety Authority (EFSA) has 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 is assigned their ADI based on rigorous testing and research commissioned by EFSA. The evidence is constantly being re-evaluated. The ADIs are often set to levels much higher than would be reasonably possible for most humans for additional safety reasons. For example, the ADI for sucralose is set at 15mg per kilogram of body weight per day [9]. For a 70kg person, this would be 1050mg per day – the equivalent to 83 sachets of Splenda!

2. Health

Although safe to consume, 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. Although most sweeteners do not contain calories, it's thought their sweet flavour fires off the same reward centres of the brain as sugar, meaning we feel the same happy feeling as we do with the real deal. By feeding these pleasure centres, this also 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 lower our tolerance for sweetness becomes. This has shown to increase our intake of sugar and calories overall [10]. One study found that the sweetener sucralose actually illicted a stronger increase in appetite than sugar, particularly in women and those classed as obese [11], although this may not necessarily evoke weight gain according to a recent review [12].

It's been suggested that artificial sweeteners may disrupt gut bacteria [13]. 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 [14]. A chronic imbalance in the gut microbiome has also been associated with obesity [15], so it may be especially important to prioritise a healthy gut if you're concerned about your weight. Although several studies have identified a link between artificial sweetener intake and poor gut bacteria [16, 17], more research is needed to establish the true effect of artificial sweeteners on gut microbiota.

Sweetener in tea

The bottom line

The current body of evidence places artificial sweeteners as a safe ingredient to eat in moderation as part of a balanced diet. They represent a zero-calorie alternative to sugar, which can be especially useful for anyone looking to reduce their sugar consumption, including those of us on a weight loss journey.

That said, a better solution to avoid the suggested effects on sugar cravings and the gut microbiome could be 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. This could help us to choose less processed products that contain sugars and sweeteners and nudge us towards a diet rich in whole, unprocessed foods.

Scientific opinion is constantly being updated as new research emerges. For the time being, 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.

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.