Do artificial sweeteners cause weight gain?

It’s the holy grail of the food industry: a low-calorie, safe alternative to sugar that tastes just as good. With mounting concerns that sugar is fuelling the global obesity epidemic, the range of alternative sweeteners is growing.

But, asks Sue Quinn, are sugar substitutes all sweetness and light – or do they come with a bitter aftertaste?

Do artificial sweeteners cause weight gain?

Sugar substitutes have been around for almost 140 years – saccharin was first produced in 1879 and used during World War II when the white stuff was in short supply. These days, we consume vast quantities of sweeteners. According to market research analysts Euromonitor, more than 2 million tonnes of ‘high intensity sweeteners’, as they’re sometimes known, were consumed in food and drink products in the UK in 2016. The European Food Information Council says sales of low-calorie soft drinks have increased 15-fold over the past 30 years and have become best sellers.

What are sweeteners?
Alternative sweeteners are low-calorie or calorie-free sugar replacements used to sweeten food and drink. They’re also available as ‘table-top sweeteners’ to stir into tea and coffee or sprinkle over cereal.

Sweeteners are anything from 200 to 650 times sweeter than sugar and contain almost no calories (between 0-4kcal/g). Because they’re intensely sweet, only tiny amounts are needed, so they can satisfy a sweet tooth without racking up the calories.

There are different kinds of sweetener: artificial, ‘non-nutritive’ or intense sweeteners are calorie-free and often found in food and drinks labelled ‘diet’, ‘calorie-free’ or ‘no sugar’. The most common ones in the UK include acesulfame K, aspartame, saccharin and sucralose (see box, right). Nutritive sweeteners contain energy in the form of carbohydrates, so they’re low-calorie but not calorie-free. Common forms include fructose and others ending in ‘ol’ such as sorbitol and xylitol. Natural sweeteners include calorie-free stevia, extracted from the Stevia rebaudiana plant, as well as honey, agave, coconut sugar, molasses, brown rice syrup and maple syrup.

Are they safe?
Over the decades there have been many safety scares about alternative sweeteners. Some early animal studies, later disproved, suggested links to cancer. More recent independent animal studies have suggested they might cause health issues, including neurological and liver problems. Detractors say some sweeteners haven’t been studied adequately and that studies declaring them safe weren’t impartial because they were sponsored by the companies that manufacture them.

However, all modern sweeteners have to undergo rigorous safety checks and be approved by the European Food Safety Authority. And both Cancer Research UK and the US National Cancer Institute have said sweeteners don’t cause cancer. “Large studies looking at people have now provided strong evidence that artificial sweeteners are safe for humans,” states Cancer Research UK.

But even if sweeteners are safe, the question remains: are they healthy options? There’s conflicting evidence. Emerging research indicates that, rather than helping with weight loss, long-term consumption might actually have the opposite effect and cause weight gain.

The benefits
The European Food Safety Authority has approved claims by manufacturers that sweeteners help prevent tooth decay, control blood sugar levels and reduce calorie intake. An enquiry into carbohydrates and health by the Government’s Scientific Advisory Committee on Nutrition (SACN) in 2015 also concluded they were safe.

“Replacing sugar with sweeteners in our foods and drinks can reduce the number of calories consumed, helping us to achieve and maintain a healthy weight,” says Professor Louis Levy, head of nutrition science at Public Health England. “Our latest evidence review suggests sweeteners are safe and have a role in tackling obesity.”

…and some concerns
Some studies suggest that consuming artificial sweeteners over the long term is likely to make people gain weight. An investigation published in the Canadian Medical Association Journal underwent a review of 37 studies involving more than 400,000 people. It found a link between regular consumption of sweeteners and weight gain, obesity, high blood pressure, diabetes, heart disease and other problems. “Given the increasing use of non-nutritive sweeteners, caution is warranted until the risks and benefits of these products are fully characterised,” the study concluded.

It’s unclear why sweeteners might trigger weight gain. It could be the body becomes confused when it consumes something sweet that has no calories, triggering hunger. Another theory is that sweeteners fuel sugar cravings, or alter our gut bacteria in a way that impairs our ability to control blood sugar levels.

In theory at least, sweeteners don’t raise blood sugar levels the way sugar does, so are considered safe for diabetics. However, a study given to the European Association for the Study of Diabetes last year found that sweeteners can interfere with the way the body processes glucose. The University of Adelaide’s Dr Richard Young, who led the study, says: “High regular consumption of artificial sweeteners may be a path to poorer blood sugar control in humans.” This could cause spikes in blood sugar and increase insulin resistance, which is when the body fails to keep blood glucose levels under control. “This, in turn, could increase the risk of developing type 2 diabetes, obesity and cardiovascular diseases,” Dr Young says. Research is set to continue.
Harvard School of Public Health advises low-calorie drinks are best consumed in small amounts over a short period of time. And because the long-term effects of these sweetened drinks ‘are unknown’, the advice is for children to avoid them.

The bottom line
Alternative sweeteners are widely regarded as safe, but emerging evidence suggests that consuming large quantities over the long-term may have health implications including weight gain.

True or false?

  • Official heath policy states that alternative sweeteners can help weight loss: TRUE
  • The long-term effects of consuming large quantities of sweeteners are unknown: TRUE
  • Evidence suggests long-term consumption of large quantities of sweeteners might increase the risk of type 2 diabetes, obesity and cardiovascular disease: TRUE
  • Some medical experts suggest drinks containing sweeteners are unsuitable for children: TRUE
  • According to a theory, sweeteners might trigger sugar cravings: TRUE

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