What is E951? (Food Additive Explained)
E951 is aspartame — the world's most widely used artificial sweetener, approximately 200 times sweeter than sugar. It's the sweetener in Diet Coke, Pepsi Max, and thousands of sugar-free and low-calorie products. It's one of the most studied food additives in history.
What is E951?
Full name: Aspartame
E951 is aspartame, a synthetic dipeptide made from two amino acids: aspartic acid and phenylalanine. It was discovered accidentally in 1965 by chemist James Schlatter and has been commercially available since the 1980s. It's sold under brand names including NutraSweet and Equal. Unlike acesulfame K, aspartame is not heat-stable — it breaks down at high temperatures, which limits its use in cooked products. Products containing aspartame must carry the warning 'Contains a source of phenylalanine' for people with phenylketonuria (PKU).
What does E951 do in food?
E951 provides intense sweetness at virtually zero calories. When consumed, it's broken down into its component amino acids (aspartic acid and phenylalanine) and a small amount of methanol — all of which occur naturally in far larger quantities in ordinary foods like fruit, milk, and meat. A can of Diet Coke contains approximately 180 mg of aspartame. It's the dominant sweetener in the diet drinks market and is often combined with acesulfame K (E950) for a more rounded taste.
Where is E951 found?
E951 is commonly found in:
- Diet Coke, Pepsi Max, and diet soft drinks
- Sugar-free chewing gum and mints
- Tabletop sweeteners (NutraSweet, Equal, Canderel)
- Low-calorie yoghurts and desserts
- Sugar-free squash and cordials
- Some medicines and supplements
Is E951 bad for you?
Aspartame is one of the most thoroughly studied food additives in history, with over 200 scientific studies reviewed by regulatory bodies. EFSA, the FDA, and the WHO's Joint Expert Committee on Food Additives (JECFA) have all concluded it is safe at current intake levels, with an ADI of 40 mg/kg body weight per day. In July 2023, the WHO's International Agency for Research on Cancer (IARC) classified aspartame as 'possibly carcinogenic to humans' (Group 2B) — the same category as aloe vera and pickled vegetables. Crucially, JECFA simultaneously reaffirmed the existing ADI, stating that normal consumption poses no concern. The only definitive health risk is for people with PKU (phenylketonuria), a rare genetic condition that prevents phenylalanine metabolism.
Why E951 matters for food choices
Aspartame sits at the centre of the ultra-processed food debate. Diet and zero-sugar drinks are among the most consumed ultra-processed products in the UK, and aspartame is a key ingredient in many of them. Under NOVA, artificial sweeteners are defining characteristics of Group 4 ultra-processed foods — substances that don't exist in home kitchens and serve to make industrial products hyper-palatable. The question isn't just whether aspartame is safe in isolation, but whether the ultra-processed products it enables are the best dietary choice.
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