Is diet soda bad for you?

Coco-Cola is launching a new ad campaign to defend artificial sweeteners in diet soda Aaron Carroll: It's no surprise, since sales of diet soda is dropping more than regular soda He says there's little evidence to support the idea that artificial sweeteners pose health risk Carroll: Given a choice, it's still better to choose sugar-free soda over sugared soda

Editor's note: Dr. Aaron E. Carroll is an associate professor of pediatrics at the Indiana University School of Medicine and the director of the university's Center for Health Policy and Professionalism Research. He blogs about health policy at The Incidental Economist and tweets at @aaronecarroll.

(CNN) -- For some time, sugary soft drinks have been under attack as a major contributor to the obesity epidemic plaguing the nation, if not the world. As a result, sales of regular soft drinks have been dropping. Apparently, sales of diet soft drinks have taken even more of a hit.

So it comes as no surprise that Coca-Cola is planning to launch a new ad campaign defending -- and promoting -- its diet soft drinks.

The ads are going to focus on the safety of artificial sweeteners, or aspartame, in diet soda. Coca-Cola must believe that some of the fall in sales is due to concerns over the health effects of artificial sweeteners.

Aaron Carroll

Here's the thing: There's a lot of science out there, and it's hard to say that aspartame holds much of a health risk.

Aspartame was first approved for use in 1981, but it wasn't until 15 years later that health concerns showed up. In 1996, a research paper showed that there had been a recent increase in brain tumors and hypothesized that this might be due to aspartame. Mind you, it didn't prove that was so. But the potential link was all the media needed to go crazy. TV shows, magazine articles, and newspapers all questioned whether the artificial sweetener was safe.

Further work using data from the National Cancer Institute showed that the increase in brain tumors really began in 1973, long before aspartame was introduced. Moreover, the increases in incidence of cancer were seen primarily in the elderly, which as a group, was not the major consumer of diet soda.

And there's more. A randomized, double-blind, placebo controlled trial showed that aspartame didn't affect memory, behavior or mood. And a study published in 2006 followed more than 285,000 men and almost 190,000 women and couldn't detect any relationship between aspartame and brain or blood cancer.

Some research has shown that drinking artificially sweetened beverages doesn't promote weight loss, or even promotes weight gain. More often than not, this is because people wind up overcompensating for the calorie savings they think they're getting by switching beverages (think of the person who orders dessert as a reward for having diet soda). But in those cases it's not the diet beverage that caused weight gain; it's dieters' behavior.

You can even find people who postulate that artificially sweetened beverages trick the brain into wanting more calories. There's really no proof of that. Finally, some will claim that diet drinks will cause the brain to release insulin, which can change your metabolism and make you hungry. That's a bit hard to swallow. That's like saying if you ate sugar-dense food that tasted terrible, it would trick your brain into not releasing insulin. It's the pancreas that releases insulin anyway, not the brain.

The bottom line is that artificially sweetened beverages are safe. That doesn't mean you should drink tons of them. My wife and I limit our kids' consumption of soda to caffeine-free, diet types. But we don't let our children drink them every day. We stress moderation in everything.

The fact that Coca-Cola and other companies are seeing sales drop across the board is likely to create a backlash against artificial beverages in general. It's hard to get too upset about that, since our consumption of them was likely too high to begin with.

But we shouldn't make the perfect the enemy of the good. Given a choice between a sugared soda and a sugar-free soda, I'd rather see my kids choose the latter every time. There's an abundance of evidence that the sugar is contributing to health problems; there's not much conclusive evidence that artificial sweeteners in diet sodas are doing the same.

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