Aspartame (E951): The World's Most Controversial Sweetener

TL;DR

Aspartame (E951) is the most famous artificial sweetener in the world, found in everything from Diet Coke to chewing gum. It is 200 times sweeter than sugar but has zero calories. In 2023, the World Health Organization (WHO) classified it as a "possible carcinogen" (Group 2B), reigniting safety debates. Kale rates it as Caution (Orange).

What is Aspartame (E951)?

Aspartame is a synthetic dipeptide composed of two amino acids: aspartic acid and phenylalanine. When your body digests it, it breaks down into these two amino acids plus a small amount of methanol (wood alcohol).

Because it is so intensely sweet, only tiny amounts are needed to replace sugar, making it the king of "diet" products for the last 40 years.

Where is it found?

It is ubiquitous in low-calorie products.

• Diet Sodas: Diet Coke, Coke Zero, Pepsi Max, Sprite Zero.
• Tabletop Sweeteners: Equal (the blue packets) and NutraSweet.
• Chewing Gum: Almost all sugar-free gum brands (Orbit, Trident, Extra).
• Yogurts: "Light" or "Fit" low-calorie yogurts.
• Drink Mixes: Crystal Light and sugar-free gelatin powders.
• Cough Drops: Sugar-free lozenges.

Health Concerns

1. WHO Classification: "Possible Carcinogen"

In July 2023, the International Agency for Research on Cancer (IARC), largely due to limited evidence suggesting a link to liver cancer (hepatocellular carcinoma).

It's important to note that "Group 2B" means the evidence is not conclusive (unlike tobacco or asbestos), but it's a signal that more research is needed. The FDA disagrees with this finding and maintains that aspartame is safe.

2. Phenylketonuria (PKU)

People with the genetic disorder PKU cannot metabolize phenylalanine. For them, aspartame is toxic and can cause brain damage. This is why every product containing aspartame must carry the warning: "Phenylketonurics: Contains Phenylalanine."

3. Headaches & Neurological Symptoms

Anecdotally, thousands of people report getting headaches, migraines, or brain fog after consuming aspartame. While double-blind studies have had mixed results, "aspartame sensitivity" is a real phenomenon for many individuals.

Kale's Verdict: Caution (Orange)

Kale rates E951 (Aspartame) as Caution (Orange).

We don't rate it Red because the evidence for cancer in humans is limited, and occasional consumption is likely safe for most people.

However, we rate it Orange because:

1. Chemical Complexity: It breaks down into methanol, which is toxic in large doses (though food sources like tomato juice also contain methanol).
2. Gut Health: Emerging research suggests it may negatively impact the gut microbiome.
3. Better Alternatives: With natural options like Stevia and Monk Fruit widely available, there is less need to rely on synthetic sweeteners.

How to Avoid It

1. Check for "Phenylalanine": The mandatory PKU warning is the easiest way to spot it.
2. Scan with Kale: We'll flag E951 instantly.
3. Read the Specs of "Diet" Drinks: Don't assume "Zero Sugar" means healthy.
4. Chew "Aspartame-Free" Gum: Brands like Pür and Glee Gum use Xylitol instead.

Final Thoughts

Aspartame probably isn't the deadly poison internet conspiracy theories claim it is, but it's certainly not a health food. If you drink a gallon of diet soda a day, you might want to reconsider. For the occasional treat, it's likely fine—but we prefer our sweetness from nature, not a lab.

Still drinking diet soda? Download Kale to see what else is in that can.