Many people think of diet sodas as healthy, low-calorie alternatives to sugary drinks. Yet a small but growing body of evidence suggests that diet sodas may have health downsides and may not even provide the benefits some people turn to them for, such as weight loss.
“Excess sugar intake is a problem in Western society because it contributes to obesity, diabetes, and other conditions,” says Matthew P. Pase, Ph.D., a research fellow in neurology at the Boston University School of Medicine. “We know that diet beverages are becoming more popular, but we don’t have a lot of research into the effects of diet beverages on different aspects of health.”
The strongest evidence so far links regular diet soda intake with cardiovascular conditions, such as stroke and heart attack, as well as type 2 diabetes and obesity (which are also risk factors for cardiovascular disease), says Ralph L. Sacco, M.D., professor of neurology at the University of Miami Miller School of Medicine. For example, in April, a widely reported study of about 4,400 people age 45 and older found that those who drank one or more diet sodas every day were three times more likely to have a stroke than those who didn’t, says Pase, who led the study. The research was published in the American Heart Association journal Stroke.
Past research has also found links between diet sodas and conditions such as depression or pre-term delivery. For example, one study of almost 320,000 people published in the journal PLoS One in 2014 found that those who drank four or more cans of diet soda each day were about 30 percent more likely to be diagnosed with depression than those who didn’t.
A Cautious Interpretation
The studies linking diet sodas and cardiovascular risk are intriguing, says Sacco, but they still need to be repeated in more rigorous settings. For example, he says, all of these studies relied on participants self-reporting their dietary habits, which can introduce error because people don’t always remember what they ate. Additionally, those who drink diet sodas may already be at increased risk of conditions such as diabetes or obesity because they are unhealthy to begin with. For example, someone who is overweight may have switched from regular soda to diet soda to help control an already burgeoning waistline.
And not every study has shown that diet sodas negatively affect health. For example, in 2012 researchers from the Harvard School of Public Health analyzed the drinking habits of almost 43,000 men and found that those who drank sugary drinks had a higher risk of coronary heart disease, but those who drank diet sodas did not.
What to Do
“In general, your best bet is to avoid regular and diet sodas altogether,” says Orly Avitzur, M.D., Consumer Reports’ medical director. “They offer little nutritional benefit, and in some cases, diet sodas can cause headaches or make you overeat.” For example, shortly after the artificial sweetener aspartame came onto the market in the late 1990s, one of the biggest complaints the Food and Drug Administration received about the sweetener was regarding headaches.
In the end, the occasional soda—with sugar or artificial sweeteners—is probably fine. But your best bet the vast majority of the time, says Avitzur, is to stick with water, plain or sparkling. If you find unflavored water boring, add a splash of bitters with a slice of lemon or lime.