Aspartame: What is it and how much Diet Coke is safe to drink?

The artificial sweetener has been classified as 'possibly carcinogenic to humans' but experts say it is safe to consume in limited quantities.

Advice on how much aspartame people can eat or drink remains unchanged, despite the artificial sweetener being classified as “possibly” causing cancer.

Widely used as an artificial sweetener since the 1980s, aspartame is used in diet drinks, chewing gum, gelatine, ice cream, dairy products such as yoghurt, breakfast cereal, toothpaste and medications such as cough drops and chewable vitamins.

In a report released late on Thursday, the WHO’s International Agency for Research on Cancer (IARC) classified aspartame as “possibly carcinogenic to humans”.

But a panel of experts has said the sugar substitute aspartame is safe in limited quantities.

What is aspartame?

Aspartame is a non-nutritive sweetener, which means it contains zero or very few calories and provides no vitamins or minerals.

It was discovered by accident in the lab by American chemist James Schlatter in 1965 after he licked it off his finger – against work safety regulations.

Mr Schlatter was hunting for anti-ulcer drugs when he found that aspartic acid and phenylalanine, two naturally occurring amino acids (molecules used by all living things to make proteins), when mixed with methanol, a simple alcohol found in fruits and vegetables, produced a substance with intense sweetness.

Thus aspartame was born and eventually approved for use in food products in Canada 15 years later.

In 1983, approval was granted by the US Food and Drug Administration and other countries followed suit.

Aspartame is around 200 times sweeter than regular table sugar and is now widely as a table-top sweetener as well as in products such as diet fizzy drinks, chewing gum, breakfast cereals and cough drops.

Is Diet Coke safe to drink?

Yes, in moderation. The WHO say a person weighing 70kg would need to consume more than between nine and 14 cans of diet soft drink per day to exceed the daily guideline.

The Food and Agricultural Organisation’s Joint Expert Committee on Food Additives, which carried out a complementary study, retained its advice that it is safe for a person to drink 0-40mg per kilogram of body weight each day.

Most people consume less than the safe upper limits of aspartame, but the WHO recommends heavy consumers cut down.

What does ‘possibly carcinogenic to humans’ mean?

A substance that is carcinogenic has the potential to cause cancer.

IARC uses four possible classifications related products that may be associated with cancer risk: carcinogenic to humans (Group 1), probably carcinogenic to humans (Group 2A), possibly carcinogenic to humans (Group 2B) and not classifiable (Group 3).

Aspartame has been listed as “possibly carcinogenic” alongside other substances such as aloe vera and lead.

This decision is mainly based on three studies suggesting an association with a type of liver cancer.

Paul Pharoah, professor of cancer epidemiology at the Cedars-Sinai Medical Centre in Los Angeles, said: “In short, the evidence that aspartame causes primary liver cancer or any other cancer in humans is very weak.

“This is why it is classified as Group2B. Other examples of classified as Group2B are extract of aloe vera, diesel oil, caffeic acid found in tea and coffee.”

What is the advice from the WHO?

Dr Francesco Branca, director of the WHO’s department of nutrition and food safety, said: “The assessments of aspartame have indicated that, while safety is not a major concern at the doses which are commonly used, potential effects have been described that need to be investigated by more and better studies.

“We’re not advising consumers to stop consuming (aspartame) altogether.

“We’re just advising a bit of moderation.”

The WHO said it and the IARC will continue to monitor evidence and encourage independent research groups.

What have independent experts said about this decision?

Gunter Kuhnle, professor of nutrition and food science at the University of Reading, said the move illustrates the “importance of distinguishing between hazard and risk”.

He said: “Sunlight is a hazard as it can cause cancer, but the risk depends on the amount of sunlight and whether we use protection.

“Likewise, even if aspartame causes cancer at very high amounts, there is no risk when consuming it at the amounts that are permitted in foods.”

Dr Duane Mellor, registered dietitian and senior lecturer at Aston Medical School, Aston University, said the guidance does not mean people should start consuming aspartame – and other non-nutritive sweeteners – more often as an earlier report from the WHO found no beneficial link between sweeteners and weight management.

He said water is still the healthiest option for most people but if a sweetened drink is desired, using non-nutritive sweeteners as a way of reducing sugar intake “would be sensible”.

What is the advice in the UK?

In the UK, aspartame is considered a safe and acceptable alternative to sugar, with the NHS specifying all available sweeteners “undergo a rigorous safety assessment” before they can be used.

The law determines how much sweetener can be used and in which products.

As part of the evaluation process, the UK Government sets an acceptable daily intake, which is the maximum amount considered safe to consume every day.

The NHS adds that, while there have been reports that use of sweeteners is linked to other health issues, the evidence base for this is limited.

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