Introduction
For those of us with a sweet tooth, being able to have our favourite soft drink or latte without the extra sugar and calories can seem like the perfect hack. But many people think it sounds too good to be true. Is there a trade-off? Cancer? Heart disease? Diabetes?
With the introduction of the UK sugar tax, many readily available soft drinks now contain artificial sweeteners instead of, or alongside, sugar. But what does the evidence actually show about their benefits and risks?
What are artificial sweeteners?
Artificial sweeteners are low- or no-calorie alternatives to sugar. Common examples include aspartame, sucralose and saccharin. They are many times sweeter than ordinary sugar, meaning only very small amounts are needed to make foods and drinks taste sweet.
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How do we know artificial sweeteners are safe?
Before a sweetener can be used in food and drinks in the UK, it must undergo a safety assessment. Regulators use this evidence to set an acceptable daily intake (ADI) — the amount that can be consumed every day over a lifetime without an appreciable health risk.
The ADI also includes a large safety margin. It is usually set at around 100 times lower than the highest intake shown not to cause harmful effects in animal studies.
For example, the ADI for aspartame is 40 mg per kilogram of body weight per day. For a 70 kg adult, that's 2,800 mg per day. A can of diet soft drink typically contains considerably less than this, although the exact amount varies between products.
The NHS states that all sweeteners approved for use in Great Britain are considered safe to consume within these limits. The exception is people with phenylketonuria (PKU), who need to avoid aspartame because it contains phenylalanine.
What does the evidence show?
One of the biggest concerns surrounding artificial sweeteners is whether regularly consuming them could increase the risk of conditions such as diabetes, cardiovascular disease or cancer.
A large systematic review commissioned by the World Health Organization found that, in randomised controlled trials, consuming non-sugar sweeteners had no significant effect on fasting glucose, insulin or HbA1c. There was also no significant effect on LDL cholesterol or blood pressure.
When looking at cancer, long-term cohort studies found no association between higher sweetener intake and overall cancer risk or cancer mortality.
However, the picture becomes more complicated when we look at other long-term observational studies. People consuming larger amounts of sweeteners had higher rates of type 2 diabetes, cardiovascular disease and overall mortality.
This does not necessarily mean that sweeteners caused these conditions. People who are already overweight or at higher risk of diabetes may be more likely to choose diet drinks and artificial sweeteners in an attempt to reduce their sugar intake. This makes it difficult to separate cause and effect.
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What about cancer?
One of the most common concerns about artificial sweeteners is whether they increase the risk of cancer. In the WHO systematic review, prospective cohort studies found no significant association between higher intake of non-sugar sweeteners and overall cancer risk or death from cancer.
Some individual studies have reported associations between particular sweeteners and specific cancers. However, these findings have not been consistent across studies and, importantly, an association does not prove that the sweetener caused the cancer.
Overall, this systematic review did not find evidence that consuming more non-sugar sweeteners increases your overall risk of developing or dying from cancer.
So are sweeteners better than sugar?
It depends on what you're replacing.
If artificial sweeteners replace sugar, they can be a useful way of reducing your sugar and calorie intake and may result in a small reduction in body weight. Unlike sugar, they also don't contribute to tooth decay.
But that doesn't mean adding artificial sweeteners to your diet will make you healthier. The evidence doesn't show a benefit from choosing a diet drink over water, for example.
The long-term evidence is less straightforward. Although observational studies have found associations between high sweetener consumption and conditions such as diabetes and cardiovascular disease, they cannot prove that sweeteners are responsible.
So swapping a sugary drink for a diet version can be a useful way to cut down on sugar, but there is no need to start adding artificial sweeteners to your diet for their supposed health benefits.
Emerald's take
Artificial sweeteners aren't a health food, but the evidence doesn't support the idea that approved sweeteners are inherently harmful when consumed within recommended limits.
The key question is what are you replacing? If swapping a sugary soft drink for a diet version helps you reduce your sugar and calorie intake, artificial sweeteners can be a useful alternative and may help with weight management. But replacing water with a diet drink isn't going to make you healthier.
You don't need to be afraid of the occasional Diet Coke, but you don't need to seek out artificial sweeteners for their health benefits either. Think of them as a tool for reducing sugar rather than something that actively improves your health.
References
Rios-Leyvraz M, Montez J. (2022). Health effects of the use of non-sugar sweeteners: a systematic review and meta-analysis. World Health Organization.
NHS. (2022). The truth about sweeteners. NHS.
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