Two groups linked to the World Health Organization on Friday said that aspartame, a popular artificial sweetener used in thousands of products worldwide such as Diet Coke, ice cream and chewing gum, is a possible cause of cancer, but it remains safe to consume in moderation.

What is aspartame?

Aspartame is a low-calorie artificial sweetener 200 times sweeter than sugar. It is widely used in various food products and beverages such as ice creams, chewing gum, gelatin, yogurt, breakfast cereal and toothpaste. It is also used in medications such as cough drops and chewable vitamins as well as soft drinks like Diet Coke, Coke Zero, Pepsi Max and 7 Up Free.

The demand for artificial sweeteners in food products is driven by consumers who watch their calorie intake. A high-calorie diet is known to increase the risk of obesity and diabetes.

Aspartame was approved for consumption by the United States Food and Drug Administration in 1974, with the acceptable daily intake set at 50 milligrams per kilogram of body weight. The drug regulator, however, has said that its consumption should be avoided by those who have difficulty metabolising phenylalanine, a component in the sweetener. A rare genetic disorder called phenylketonuria causes difficulty in digesting phenylalanine.

What has the WHO said?

Two World Health Organization committees – the International Agency for Research on Cancer and the Joint Expert Committee on Food Additives – conducted independent but complementary reviews to assess the carcinogenic, or cancer-causing, hazard and other health risks associated with the aspartame consumption. Their findings were released on Thursday.

The cancer research agency had convened its working group of 25 independent experts from 12 different countries to assess the risks posed by the artificial sweetener in June. The expert group classified aspartame as possibly carcinogenic based on studies in humans and animals that found “limited” evidence that it may be linked to liver cancer. This classification is known as Group 2B. The International Agency for Research on Cancer uses four strength-of-evidence classifications:

  • Group 1: Carcinogenic to humans.
  • Group 2A: Probably carcinogenic to humans.
  • Group 2B: Possibly carcinogenic to humans.
  • Group 3: Not classifiable.

The Group 2B classification is generally used either when there is limited but not convincing evidence for cancer in humans or there is convincing evidence for cancer in experimental animals, but not both.

The Joint Expert Committee on Food Additives conducted a separate evaluation by 13 members and 13 experts from 15 countries in Geneva from June 27 to July 6. They concluded that there was no convincing evidence from experimental animal or human data that aspartame had adverse effects.

They based their conclusion on the fact that aspartame is fully hydrolysed in the gastrointestinal tract into metabolites that are identical to those absorbed after consumption of common foods, and that no aspartame enters the systemic circulation as such.

The committee said that the data evaluated indicated no reason to change its previously established acceptable daily intake of zero to 40 milligrams per kilogram of body weight for aspartame.

In simple terms, a 300 milliliter can of diet soda contains 200 to 300 milligrams of aspartame. Hence, an adult weighing 70 kg would need to consume nine to 14 cans a day to exceed the acceptable daily intake level, assuming no additional aspartame has been consumed.

What does it mean for you?

The International Agency for Research on Cancer’s latest classification only reflects the strength of scientific evidence on whether aspartame can cause cancer in humans, it does not reflect the risk of developing cancer at a given exposure level. The types of exposure, the extent of risk, the people who may be at risk, and the cancer types linked with it can vary.

The agency evaluates evidence related to the caused of cancer but does not make health recommendations.

In the past, the agency has classified aloe vera extract, Asian-style pickled vegetables, dry cleaning, engine exhaust, occupational exposure to hard bitumens and their emissions during mastic asphalt work and carpentry work as possible cancer risks.

Meanwhile, the Joint Expert Committee on Food Additive programme undertakes risk assessment, which determines the probability that a specific type of harm, cancer in this case, will occur under certain conditions and levels of exposure.

Their assessment is based on the identified hazard properties of an agent and the anticipated exposures in specific scenarios, thus considering the routes, conditions, frequency, and levels of exposure.

“We’re not advising consumers to stop consuming aspartame altogether,” WHO nutrition director Dr Francesco Branca told the Associated Press. “We’re just advising a bit of moderation.”

He also added that the WHO advises food manufacturers in general to “use ingredients that do not require the addition of too much sugar”. Following the latest assessments of aspartame, Branca said, using sweeteners “is probably not the way forward”.

What do big beverage makers say?

The American Beverage Association, which represents the country’s non-alcoholic beverage industry, said that the artificial sweetener was safe for consumption.

“Aspartame is safe,” the association’s CEO, Kevin Keane, said on Thursday. “After a rigorous review, the World Health Organization finds aspartame is safe and ‘no sufficient reason to change the previously established acceptable daily intake.’”

He added: “The purpose and expertise of food safety agencies is to ensure safety over time. The WHO has done this again, rigorously and definitively, with aspartame.”