Many people assume that it's the artificial sweeteners that make diet soda bad for you—as in the numerous Internet rumors linking aspartame, the most widely used artificial sweetener in diet sodas, to everything from cancer to multiple sclerosis to Gulf War syndrome. Those rumors have never been confirmed, but a new study does cast doubt on the ubiquitous sweetener, suggesting that it could speed up the decline of your kidneys.
THE DETAILS: The research, presented at the American Society of Nephrology's annual Renal Week conference, included data collected from 730 diabetic women participating in the long-running Nurses' Health Study. The women had supplied data at three points over the course of six years on how often they consumed sugar-sweetened beverages or artificially sweetened sodas—less than once a month, one to four times per month, two to six times per week, one to two per day, or more than two per day. The researchers then collected data on blood tests that had been performed 11 years apart to look for certain elements that signal healthy kidney functioning. After adjustments for age, diet, and lifestyle factors like smoking, the data revealed that women who drank more than two diet sodas per day had a twofold increase in risk for kidney function decline.
WHAT IT MEANS: Don't assume that diet sodas are the healthier choice just because they're calorie-free. "I don't see a need to drink sodas at all," says study author Julie Lin, MD, MPH, an assistant professor of medicine at Harvard Med School and an associate physician in the renal division of Brigham and Women's Hospital. "Just drink water or something natural."
She did note that aspartame may not be the culprit, since the researchers didn't have the data available to differentiate between it and other artificial sweeteners like saccharin and acesulfame. But because aspartame was the most widely used sweetener in the '80s, when most of their data was collected, it looks pretty guilty, she adds. The researchers were able to narrow the effects to artificial sweeteners, she says, because they didn't see the same declines in kidney function among women who consumed high amounts of sugar-sweetened drinks. And the effects appear to be cumulative, considering that when they compared the most recent data with the data averaged over the six-year period, the association wasn't as strong in the shorter, most recent period.
Here are some ways to control your diet soda intake, and find other ways to keep your kidneys healthy:
• Exert a little portion control. If you really can't give up a daily diet soda, don't panic. "We didn't see any association between one soda a day and kidney function decline," says Dr. Lin. In her study, Dr. Lin says that the average serving size was a 12-ounce can. But walk into any convenience store today, and you're likely to see nothing but 20-ounce bottles, and at fast-food joints, a "small" could be 16 ounces or more. So keep your servings small, and pour yourself a 12-ounce glass or less.
• Drink your soda with veggies, not chips. Another study that Dr. Lin presented at the conference found that higher intakes of salty foods were also likely to speed kidney function decline. "I could imagine that someone eating a lot of salty snacks and drinking lots of sodas at the same time could be doing real damage," she says. So at least make a rule not to combine the two. Better still, skip the salted junk food and wash down your fruits and veggies with water, iced tea, or 100 percent unsweetened fruit juice.
• Switch to water—but not too much. "People have this idea that it's good to flush out your kidneys" by drinking lots of water, says Dr. Lin, and that's largely untrue. "Your body tells you when you need to drink and when you don't." In fact, drinking too much water can dilute the levels of salt in your body to the point where you can become ill, she says. "If you drink a lot of water to the point where you have to go to the bathroom a lot, that's too much water. Your body's very smart about that," she adds. "It's why your kidneys keep your body in balance."
• Filter your water. Mercury, a contaminant in some municipal water supplies, may cause kidney damage. But you can remove it with inexpensive carbon water filters used in pitchers and faucet-mounted filter systems.
Published on: November 5, 2009
Updated on: January 15, 2013