In Laura West's household, a 24-pack of Diet Coke lasts about a week. She drinks two or three a day, her 15-year-old-son Michael at least that many.
"I've always been associated with Diet Coke," says West, 45, an avid runner who lives in Plano, Texas. "If people don't know what to get me, they get me Diet Coke" memorabilia.
She and Michael have gone through phases when they "try to be good" and cut down on their consumption, she says. But "at this point, I don't have that many bad habits. If there was a study to come out saying it shortens your life by five years, I'd probably stop or try to stop."
West might be right in being at least a little concerned. Although consuming something with no sugar might sound healthy, and beverage-makers offer evidence that the drinks can indeed help with weight loss, independent health experts say the drinks are not innocuous.
Prevention magazine recently offered seven scary results of drinking diet soda, including issues with weight, kidneys, metabolism, teeth and cells.
"The fact that it has zero calories does not mean it has no consequences," says Sharon Fowler, a specialist in the Division of Clinical Epidemiology, School of Medicine at the University of Texas Health Science Center in San Antonio.
Echoes Charles W. Wakefield, a professor at Texas A&M Health Science Center Baylor College of Dentistry: "People think, 'Diet soda is so much better for me.' You see them on Sunday night buying four cases of that stuff, and it's just for one week."
His concern is teeth (more on that later). Fowler's worry, among others, is the link between diet soda and obesity.
"If you're overweight and drinking diet sodas, there's an even greater risk of weight gain than being overweight and not drinking them," she says.
Nancy DiMarco, professor of nutrition at Texas Woman's University, points out a study in the journal Microbiology and Ecology, which shows this: "People who drank one or more diet sodas a day have a five-time increase in waist circumference in 10 years compared to those who drank none."
Crazy, huh? Isn't the whole point of diet drinks to help people lose weight? Maybe, but our bodies have other ideas.
"We are designed in a way that taste matters in our body's ability to figure out how many calories we have," Fowler says. "Disrupting that makes it harder for the body to figure out."
Sweet tastes tend to be caloric, which kicks off metabolism. But if a sweet taste comes in and there's nothing to burn, she says, the body learns not to rev up.
Studies suggest that because you're not full, your metabolism will slow down, she says. "If you're never full, it will lead you to search out more food all the time. You'll eat more on a regular basis, more calories on a daily basis than you normally would."
But dietitian Marilyn Schorin, who has a doctorate in nutrition and is a consultant to the American Beverage Association, says if diet sodas were unhealthful, she wouldn't drink them.
She cites a Harvard University study in which participants who drank a diet soda a day cut daily calories by 100 and lost weight over three years. "That showed people didn't compensate by saying, 'I'll eat more of something else.'"
Schorin also offers information from the National Weight Control Registry, which keeps track of people who have lost 30 pounds and kept the weight off for at least a year. One thing registrants had in common: "They used diet soft drinks to maintain weight loss," Schorin says.
"These are palpable ingredients that can help people in their efforts" to lose weight, she says.
In so doing, are you harming your teeth? Quite possibly, says Wakefield at Baylor.
"Acidity, not sugar, is what dissolves tooth structure until it gets deeper and turns into decay," he says.
This is especially detrimental for people taking any of several hundred medications that can cause dry mouth. "If someone like you or me has normal saliva, we could sip on fruit juice, Diet Coke, lemonade, and it wouldn't bother us," Wakefield says. "But for these people, and there are a lot of them, with compromised quality or quantity of saliva, they have a problem."
If you don't have dry mouth, you still need to be careful, he cautions. Don't sip on one throughout the day and rinse your mouth with water when you finish.
Wakefield is also concerned about the link between sodas - sugared and sugar-free - and osteoporosis. Just a few of either a week can predispose people to the bone-eroding disease, he says, "particularly if consumed through the teen years into the mid-20s, the period when lifelong bone formation takes place."
So what to do with this information? Remember that diet sodas, along with their higher-calorie sugared counterparts, offer nothing nutritionally. Then again, neither do potato chips or Milk Duds. So think - yes, that most useful of M-words - moderation.
Schorin adds another: mindfulness.
"Diet sodas," she says, "are not a permission slip to eat whatever you want."