Diet cokes
Niall Kennedy

Bad news for everybody who drinks diet sodas instead of the sugary varieties to help stay healthy.

In an opinion piece [PDF] in the journal Trends in Endocrinology and Metabolism, Purdue University professor Susan Swithers writes that drinks containing such chemicals as aspartame, sucralose, and saccharin have been found to contribute to excessive weight gain, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Her piece summarizes studies on the health effects of artificial sweeteners:

Recent data from humans and rodent models have provided little support for ASB [artificially sweetened beverages] in promoting weight loss or preventing negative health outcomes such as [type 2 diabetes], metabolic syndrome, and cardiovascular events. Instead, a number of studies suggest people who regularly consume ASB are at increased risk compared with those that do not.

How is this possible? Swithers describes a number of theories, some of them relating to the effects of such sweeteners on metabolism. “Sweet tastes are known to evoke numerous physiological responses,” she writes. “By weakening the validity of sweet taste as a signal for caloric post-ingestive outcomes, consumption of artificial sweeteners could impair energy and body weight regulation.”

NPR’s Alison Aubrey put Swithers’ piece into some context:

Not everyone is convinced that diet soda is so bad.

For instance, a study I reported on last year by researchers at Boston Children’s Hospital found that overweight teens did well when they switched from sugar-laden drinks to zero-calorie options such as diet soda.

But it’s also hard to ignore the gathering body of evidence that points to potentially bad outcomes associated with a diet soda habit.

One example: the findings of the San Antonio Heart Study, which pointed to a strong link between diet soda consumption and weight gain over time.

“On average, for each diet soft drink our participants drank per day, they were 65 percent more likely to become overweight during the next seven to eight years” said Sharon Fowler, in a release announcing the findings several years back.

Another bit of evidence: A multi-ethnic study, which included some 5,000 men and women, found that diet soda consumption was linked to a significantly increased risk of both type-2 diabetes and metabolic syndrome.

If you’re choosing between a diet soda and a regular soda, then it’s probably healthier to go for the former. But these studies are a reminder that such a choice won’t keep you healthy.

It’s also worth remembering that some scientists have found that artificial sweeteners can be toxic. Some countries even require health warnings on drinks containing such products, such as this one on a can of Diet Coke sold in India:

Warning on a can of Diet Coke sold in India
John Upton