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The Diet Soda Debate

By Matt McMillen
WebMD Health News

Reviewed by Arefa Cassoobhoy, MD, MPH

July 31, 2014 -- When you're trying to lose weight or keep off extra pounds, can diet soda help? While it has fewer calories than regular soda, some studies show it fuels your sweet tooth.

Also, are artificially sweetened sodas good for your health? Several studies this year continue the debate.

Better Than Water?

In late May, the journal Obesity published a study that aimed to determine what makes a bigger difference when attempting to shed pounds: water or diet soda? The researchers found that, on average, people who drank diet soda over the course of the 12-week study lost about 13 pounds, which was 4.5 pounds more than those who had switched to water. The diet-beverage drinkers also said they felt less hungry than those who drank water.

Lead researcher James Hill, MD, says his study's results will ease the minds of diet soda drinkers who worry that it may derail their weight loss efforts, as some studies and media reports have suggested.

"The results make me confident that, at least when it comes to weight, it [diet soda] is OK," says Hill, a professor of pediatrics and medicine and an obesity specialist at the University of Colorado, Denver. "It's one less thing people have to worry about, and they have to worry about so much when it comes to weight loss."

The study was funded by the American Beverage Association, and for some, that raises the question of bias in favor of no-cal sodas.

Michael Goran, MD, says the study outcomes were solid and the research findings were significant. "But industry-funded studies always send up a red flag," he says. Goran is a professor of preventive medicine, physiology and biophysics, and pediatrics, as well as director of the Childhood Obesity Research Center, at the University of Southern California's Keck School of Medicine.

Hill says the study was thoroughly vetted by a peer-review process prior to publication. "If you're worried about industry-funded research, look at the study with a very fine-toothed comb," he says, "but, at the end of the day, evaluate the science."

Counting Calories

Earlier this year, in January, researchers at the Johns Hopkins Bloomberg School of Public Health reported that overweight and obese people who drink diet sodas tend to eat more calories during meals and from snacks throughout the day than those who drink sugary beverages, including regular soda. In adults with a healthy weight, the opposite was true: Those who drank sweetened beverages ate more than those who drank diet sodas.

Contrast this with a study published last year in the American Journal of Clinical Nutrition. It compared people who were randomly selected to swap their regular sodas for either water or diet drinks. The researchers found that both groups ate fewer calories and "showed positive changes in dietary patterns." In fact, the diet-drink group ate fewer desserts by the end of the study than the water group, while the water group ate more fruits and vegetables.

"Diet beverages have been shown to be an effective tool as part of an overall weight-management plan," the American Beverage Association says. "Numerous studies have repeatedly demonstrated the benefits of diet beverages – as well as low-calorie sweeteners, which are in thousands of foods and beverages – in helping to reduce calorie intake. Losing or maintaining weight comes down to balancing the total calories consumed with those burned through physical activity."

Artificial Sweeteners and Other Possible Health Concerns

So, do diet drinks ease the urge for other sweets? Goran believes the opposite may be true. He worries that no matter what sweetener is used -- sugar or a substitute -- the result may be a continued demand for more sweets.

"As a society, we have created a new norm of sweetness," Goran says. "We've become accustomed to high levels of sweetness."

By continuing to drink diet sodas, he speculates, "you still desire sweetness. You haven't disentangled yourself from craving something sweet."

Hill counters that the sweetness in diet soda may work to your advantage.

"People like a sweet taste, and if you take it away from beverages, then they'll probably consume more sweet calories from food," he says. "But that's just a speculation."

As a pediatrician, Goran's particularly concerned about artificial sweeteners. He says we don't yet know what long-term effects they may have on children's development. Other studies also raise concerns.

Findings presented at a March meeting of the American College of Cardiology suggest a link between drinking diet soda and a greater risk of heart attack among otherwise healthy, postmenopausal women. The researchers are quick to point out, though, that they can't explain the relationship and more study is needed.

Finally, a study in the journal General Dentistry from May of last year contends that drinking a lot of soda -- both diet and regular -- can severely damage teeth. But in this case, it's not the sweetener that's the culprit. The acid in the soda, coupled with bad oral hygiene, caused the decay.

To Drink or Not to Drink Diet Soda?

Goran says diet soda may be a good first step in the weight loss process, if you already drink a lot of regular soda or other sugary drinks. Dietician Joan Salge Blake, RD, LDN, agrees.

"They don't cause weight gain, but we don't know yet if they really help with weight loss," says Blake, who's a clinical associate professor of nutrition at Boston University. "They can be a part of a weight loss program, but they are not going to magically help you lose weight."

Goran and Blake advise soda drinkers to gradually move away from sweetened beverages altogether. Blake recommends naturally flavored, no-calorie fizzy water. Goran says his kids like their lemonade heavily watered down with seltzer.

"Ultimately," Goran says, "it's probably healthier not to drink sweetened beverages."

SOURCES: Michael Goran, MD, professor of preventive medicine, physiology and biophysics, and pediatrics; director, Childhood Obesity Research Center, Keck School of Medicine, University of Southern California. Joan Salge Blake, RD, LDN, clinical associate professor of nutrition, Boston University. Peters, J. Obesity, June 2014. Bleich, S. American Journal of Public Health, March 2014. Piernas, C. American Journal of Clinical Nutrition, February 2013. Press release, American College of Cardiology. Bassiouny, M. General Dentistry, March/April 2013.

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