PhotoThe Pepsi company announced today that, in response to consumer demand, it will stop using aspartame to sweeten its American-market diet sodas.

Starting in August, the drinks Diet Pepsi, Caffeine Free Diet Pepsi and Wild Cherry Diet Pepsi will be sweetened with sucralose and acesulfame potassium (also known as Ace-K) rather than aspartame. The recipe switch will make the various forms of Diet Pepsi the only American diet soda not sweetened with aspartame, according to the trade industry publication Beverage Digest.

Aspartame is a combination of methanol and two amino acids: aspartic acid and phenylalanine. It was invented in 1965, and in 1974 the Food and Drug Administration approved its use as a food additive. It's about 180 times sweeter than sugar, letting it impart the same amount of sweetness with a far lower caloric punch, which is why it's so popular in diet sodas.

Sugar craving

On the other hand, many reputable studies have shown that for people trying to lose weight or avoid gaining any, sugar might paradoxically be a better option than low-calorie artificial sweetener, due to chemical reactions in the brain: when you get a “sugar craving” (more specifically, when your brain generates a sugar craving), the only thing that'll satisfy the craving and make it go away is the release of dopamine, a chemical necessary for “reward signaling” in the brain.

And, as it turns out, the digestion and breakdown of sugar produces dopamine to satisfy those cravings – but the breakdown of artificial sweeteners does not. So if you have a sugar craving and eat something sugar-free, that sensation of sweetness on your tongue will not give your brain any dopamine, thus your craving does not go away, and after eating the sugar-free item you're just as likely to eat something else, to satisfy the craving.

That said, most opposition to aspartame is based not on this possible paradox, but on allegations that aspartame is harmful for human consumption. Which it is – in sufficiently high doses. But aspartame's supporters (including the FDA) say the amount of aspartame used to sweeten food isn't remotely close to that danger level. Indeed, in low doses, aspartame's two amino acids are actually necessary for the body to function properly. (If you eat a proper diet and are in generally good health, your body should actually produce a certain number of these amino acids on its own.)


As for methanol – yes, it's deadly poisonous in high quantities, but tiny amounts of it can already be found in alcoholic beverages including beer, wine and whiskey.

Paracelsus, the medieval physician now called the “father of toxicology,” famously coined the phrase “the dose makes the poison.”

In other words, any substance is poisonous in high enough doses — even those substances required for life. Even clean, healthy water will kill you if you drink too much too fast. Vitamins that are essential to good health and proper body functioning in small quantities will poison you if you eat a whole bottle of multivitamins at once. The mere fact that something is poisonous in high quantities does not necessarily mean that it's dangerous in small quantities.

Still, there remain many American consumers who say they want diet soda without aspartame, and Pepsi's plan makes it the first American soda company to offer this. But Pepsi's longtime rival the Coca-Cola company responded to the news by saying that it has no plans to change the sweeteners used in Diet Coke. “All of the beverages we offer and ingredients we use are safe,” Coke said in a prepared statement.

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