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food for thought

The International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), is expected to declare on July 14 that aspartame, a widely consumed artificial sweetener, is a possible cause of cancer in humans.

This is the latest setback for artificial sweeteners.

In May, the WHO warned consumers against using sugar substitutes for weight loss as the organization found no evidence that, over the long term, doing so provides such a benefit.

And earlier this year a zero-calorie sweetener called erythritol was tied to a greater risk of heart attack and stroke.

The most recent news that aspartame may be classified as potentially cancer-causing, reported on June 29 by Reuters, has left many people reconsidering their intake of the artificial sweetener.

Here’s what we know – and what we don’t yet know – about the IARC’s upcoming ruling and how it relates to aspartame intake advice.

What is aspartame?

Permitted for use as a food additive in Canada since 1981, aspartame is an artificial sweetener that’s about 200 times sweeter than table sugar. As such, only a small amount is needed to match the sweetness of sugar.

It’s used in thousands of light or no-sugar-added foods including soft drinks, juices, yogurts, frozen desserts, pancake syrups and chewing gum. It’s also sold as a tabletop sweetener under the brand name Equal.

Aspartame is a chemical combination of two amino acids called aspartic acid and phenylalanine. Once the sweetener is digested, the body uses these two amino acids to synthesize proteins in the body.

What does “possibly carcinogenic” mean?

The IARC assesses whether a particular agent, in this case aspartame, is capable of causing cancer in people based on the strength of the existing evidence.

The IARC has four categories for classifying the carcinogenicity of certain foods, food ingredients, chemicals and other exposures. These are class 1 (can cause cancer; processed meats are categorized here), 2a (probably causes cancer), 2b (possibly causes cancer) and 3 (not classifiable as to carcinogenicity).

Aspartame is set to be declared a group 2B possible carcinogen. This classification can mean that 1) there is some, but limited, evidence that aspartame causes cancer in humans, 2) there’s sufficient evidence it causes cancer in experimental animals or, 3) there is evidence for causal pathways that connect aspartame to cancer.

It’s been reported that the IARC reviewed 1,300 studies to arrive at its opinion on aspartame.

How large is the cancer risk?

The IARC does not assess the magnitude of cancer risk, nor does it quantify how much of a substance is considered safe. This is the job of another WHO working group, the Joint WHO and Food and Agriculture Organization’s Expert Committee on Food Additives (JECFA).

JECFA has also been reviewing aspartame this year. On July 14, immediately following the IARC’s announcement on aspartame’s carcinogenicity classification, JECFA will provide an update on the risk associated with aspartame consumption, including a review of the sweetener’s acceptable daily intake (which was established back in 1981).

Keep in mind, the IARC can identify a cancer hazard for agents even when the cancer risk appears to be very low with normal levels of exposure.

Listing aspartame as a possible carcinogen is a way to spark more research on the topic.

How much aspartame is safe to consume?

The acceptable daily intake (ADI) for aspartame, established by Health Canada in 1981, is 40 mg per kilogram of body weight. This is the same ADI that was established by the WHO.

The ADI is the amount of aspartame that would be considered safe if consumed daily for the duration of a person’s lifetime. Based on the ADI, a 68 kg (150 pound) person could safely consume 2,720 mg of aspartame a day, an amount found in 14 cans (355 ml each) of diet Coke or 73 packets of Equal.

The amount of aspartame in diet pop ranges from 75 to 190 mg per 355 ml serving. One packet of Equal contains 37 mg of aspartame.

Should you cut back on diet pop?

To make an informed decision about the consumption of aspartame-sweetened products, we need to learn more about the IARC’s evaluation.

We also need to know what JECFA concludes about aspartame based on its updated risk assessment. We will see if that assessment changes. Stay tuned on July 14th.

That said, I’ve always recommended that people limit their intake of artificial sweeteners (as well as free sugars).

There is growing evidence to suggest that regularly consuming artificial sweeteners may harm long-term health, and that should give us pause.

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD

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