Sweet taste - and safe to consume

Diet Coca-Cola is sweetened with aspartame. Photo / Brett Phibbs

Everyone who works in a chemistry lab knows that you don't use your taste receptors to check if an unknown chemical is safe or deadly poisonous (or if you do, you may do it only once). But if this hadn't inadvertently happened in one lab, the most commonly used artificial sweetener today may never have been discovered.

In 1965, a chemist working with amino acids (the building blocks of protein) created a new chemical by combining aspartic acid and phenylalanine. Some of the substance spilled on to a piece of paper lying on the laboratory bench and, not realising, the chemist licked his finger to pick it up, transferring some of the chemical into his mouth.

Luckily, he lived to tell the tale. What he had to tell was extraordinary and completely unexpected. By combining two of the building blocks of protein (which has no sweetness), he had created a substance that was about 200 times as sweet as sugar.

Dubbed "aspartame", the new chemical was found to provide virtually no kilojoules in the minute quantity needed to sweeten a beverage or solid food.

After extensive safety testing, aspartame was approved for use in Europe and the United States in the 1980s. Its use as a sweetener in a range of foods at specified levels is also permitted in Australia and New Zealand.

Indeed, it is now the most widely used artificial sweetener in the world, and is sold here under the brand name Equal.

Hoax claims about aspartame have been circulating on the internet for many years. They suggest it was first developed as an ant poison, and that it is broken down in the body to release formaldehyde, leading to health problems such as severe seizures, brain damage, lupus and birth defects. No credible scientific evidence has ever been found for any of these claims.

Of more substance is the claim that artificial sweeteners, including aspartame, may be a cause of cancer. Rat studies have shown an association between the consumption of these sweeteners and cancer incidence.

But, as the World Cancer Research Fund (WCRF) pointed out in 2007, the rat studies involved intakes "far greater than humans could consume in foods and drinks". The WCRF concluded that "the evidence ... does not suggest that chemical sweeteners have a detectable effect on the risk of any cancer".

In 2010, two studies reported possible associations between aspartame and a slight increase in adverse health outcomes. After careful review, the European Food Standards Agency (EFSA) concluded that these studies "do not give reason to reconsider previous safety assessments of aspartame".

The EFSA's latest review, last month, of the literature concludes: "There is no consistent evidence that aspartame has adverse effects, either in healthy individuals or in potentially susceptible groups."

The 2012 position paper of the US Academy of Nutrition and Dietetics also endorses the safety of aspartame by stating that "... consumers can safely enjoy a range of nutritive sweeteners and non-nutritive sweeteners (NNS)".

The position paper also points out that the estimated safe level of daily intake of aspartame over a lifetime is 50mg per kilogram of body weight. With typical intakes estimated to be in the range 0.2 to 4.1 mg/kg, the rate of consumption of aspartame by virtually everyone is likely to be less than 10 per cent of the maximum recommended level.

But there is one potential adverse health effect associated with the use of aspartame to consider - a metabolic genetic condition called phenylketonuria (a mutation that makes an enzyme non-functional) affects about one person in 10,000. People with phenylketonuria cannot metabolise phenylalanine (which, you will recall, is one of the two protein building blocks that make up aspartame), so those people need to minimise intake of all sources of phenylalanine, including aspartame.

So, can I put my hand on my heart and swear that aspartame is safe for everyone other than people with phenylketonuria?

No, I can't. Still, based on the evidence available, if I wanted to reduce my sugar intake but still enjoy sweetened tea or coffee, I would have no hesitation in using aspartame (or any of the other approved non-nutritive sweeteners).

Q&A: Just what is aspartame?

Q: What is aspartame?
A: Aspartame, a white powder, is an intense artificial sweetener used to replace sugar in foods and drinks.

Q:What is it made of?
A: Three chemicals: aspartic acid, phenylalanine, and methanol.

Q: Why is it so controversial?
A: In 1998, an inaccurate chain email circulated claiming the sweetener caused numerous health conditions. The claims were widely dismissed by major health organisations. Officials from the US Federal Drug Agency have described it as "one of the most thoroughly tested and studied food additives the agency has ever approved".

Q: So it's safe?
A: After a public consultation in January, the European Food Safety Authority concluded that aspartame and its breakdown products pose no public health and safety concerns when consumed at the average daily intake.

Q: Is it allowed in New Zealand?
A: Yes, in Australia and New Zealand it is permitted at specified levels as an intense sweetener in a range of foods.

Chris Forbes-Ewan is senior nutritionist at the Defence Science and Technology Organisation in Tasmania.

theconversation.edu.au