An artificial sweetener used in thousands of products including fizzy drinks like Diet Coke, ice cream, and chewing gum has been ruled a “possible” cause of cancer by the World Health Organisation (WHO).

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

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

The IARC has two more serious categories, “probably carcinogenic to humans” and “carcinogenic to humans”.

However, the WHO said 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, who 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.

"Cancer is one of the leading causes of death globally. Every year, 1 in 6 people die from cancer. Science is continuously expanding to assess the possible initiating or facilitating factors of cancer, in the hope of reducing these numbers and the human toll," Dr. Francesco Branca, director of the department of nutrition and food safety at WHO, said in a statement Thursday. "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."

In addition to IARC's categorization, the U.N.'s Joint FAO/WHO Expert Committee on Food Additives, or JEFCA, also provided a review on what this means for people's risk, maintaining its existing guidance on acceptable daily intake amounts.

"Our results do not indicate that occasional consumption should pose a risk to most consumers," Branca added in a press briefing. "We're not advising companies to withdraw products nor are we advising consumers to stop consuming altogether. We're just advising a bit of moderation."

Robert Rankin, president of the Calorie Control Council, an international association representing the low- and reduced-calorie food and beverage industry, said in a statement to CBS News that JEFCA's review reaffirms the overwhelming body of evidence that aspartame is safe.

"To assert otherwise is misleading, inaccurate, and fear mongering to the nearly 540 million people globally living with diabetes and millions of others managing their body weight who rely on and/or chose products that contain low- and no-calorie sweeteners such as aspartame," Rankin said.