Diet Soda May Not Be Not Your Diet Buddy!

Diet sodas have gotten a bad rap pretty much since their introduction to the marketplace. Fears that caffeine and artificial sweeteners cause cancer or that the carbonation would somehow leach the calcium from our bones have been long ago shelved, but these days some research points to possible links between diet soda consumption and increased risk of weight gain, metabolic syndrome, and yes, osteoporosis.

Thirsty for more knowledge? Duke experts weigh in on whether those links are strong enough to merit giving up a beverage that many cherish as a guilt-free indulgence.

A Dieting Detour?

The claim: Diet sodas will make you gain weight, possibly because the artificial sweeteners perpetuate your craving for sugar.

Duke physicians Howard Eisenson, Thomas Weber, Ann Brown, and Lillian Lien weigh in on the diet soda debates. Howard Eisenson, MD, executive director of the Duke Diet & Fitness Center, says there’s just not enough evidence to support that.

“The data are conflicting and limited. If there’s an association with increased weight, it could simply be because overweight people are drinking diet sodas, or because people who are drinking them are compensating for those calories elsewhere.”

In other words, you may rationalize eating a candy bar since you’ve been drinking diet soda all day — a psychological effect rather than a biological one.

Eisenson says the basic principle of weight loss is “simple, but not easy: calories in, calories out. Here at the Diet & Fitness Center, where the diet is controlled, we help keep people within their caloric range by offering diet drinks and artificial sweeteners. We say, if you must drink soda, make it a diet — but water should be the beverage of choice for adults, and for kids, water, low-fat milk, and very limited consumption of juice.”

Bones of Contention

The claim: Diet sodas may increase your risk of osteoporosis.

There’s no validity to the old claim that the carbonation in soda somehow robs the body of calcium, but all colas and some other types of sodas contain the flavoring agent phosphoric acid, a substance that may account for soda’s link to an increased risk of osteoporosis. A 2009 study showed an association between regular intake of colas and negative effects on bone.

“This is not an area that is rife with evidence,” says Duke osteoporosis specialist Thomas Weber, MD. “We need more studies, but so far the data show that an excessive intake of carbonated beverages, especially cola, appears to have somewhat of a detrimental effect on bone health. There is potentially a biological basis: if the increased acid load from soda exceeds what the kidneys can take on, the body looks to other buffers, so bone is tapped as well.”

The body may attempt to neutralize the excess acid by using calcium culled from the bones.

That theory is far from proven, though, Weber notes. The relationship between cola and bone could be from displacement — devoted soda drinkers may not be getting enough bone-strengthening nutrients such as calcium and vitamin D if they’re not drinking milk, for example.

“My advice to patients is that most things in moderation are not going to be harmful. Those who drink five, six, seven sodas a day, that’s probably where the negative impact is.”

A Sobering Association

The claim: Diet soda contributes to metabolic syndrome.

A study published in 2008 tracking the health and diet of more than 9,500 men and women over the course of nine years produced a surprising piece of data: Participants who drank one can of diet soda a day had a 34 percent higher risk than those who drank none of developing metabolic syndrome, the name given to a collection of risk factors for heart disease and diabetes.

Duke endocrinologist Ann Brown, MD, says that, although the recent study did show an association, “the finding was unexpected and calls for further investigation.” She emphasizes, “There is currently no evidence that diet sodas cause metabolic syndrome.”

Lillian Lien, MD, a Duke expert on metabolic syndrome, affirms there is still a lot to learn. “Metabolic syndrome is a constellation of factors,” including waist size and blood sugar levels, so anything that’s going to increase the number of calories consumed could contribute to it. “If someone proved that there was a link between artificial sweeteners and an increased intake of calories, that could help explain the diet soda connection.”

Otherwise, the relationship between the two remains circumstantial for now.

The link between drinking regular soda and weight gain, however, is “pretty dramatic,” says Lien. “People are not aware of the calories they’re drinking. Bottom line is that I’m still drinking diet sodas. I gave up the regular stuff a long time ago and drink a lot of unsweet tea, but that gets a little boring, so if I see a diet drink, it may be a reasonable alternative until proven otherwise. More research is definitely needed.”

Metabolic Syndrome: What’s That?

Metabolic syndrome is a group of conditions that, when taken together, are a strong indicator of a person’s risk of diabetes, heart disease, or stroke. And it’s on the rise: the American Heart Association (AHA) reports that 50 million Americans have the condition.

According to the AHA and the National Heart, Lung, and Blood Institute, a person has metabolic syndrome if he or she has three or more of these components:

• High waist circumference, based on your gender and ethnicity
• High blood levels of triglycerides or low levels of HDL (“good”) cholesterol
• High blood pressure
• High fasting blood sugar levels

These factors can all be measured at your routine visit to your doctor. If you have metabolic syndrome, your primary care physician can discuss how to treat the condition, through changes in behavior or other approaches.

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