Does drinking diet soda make any difference? It depends on the other things you put in your mouth.
By Patrick Mustain
Students line up at the fountain-drink machine in the bustling, fluorescent-lit cafeteria in Lenoir Hall on the UNC campus. Some choose lemonade, some Pepsi, while others opt for lower-calorie beverages, both water and diet sodas.
UNC sophomore Megan Brown said she always chooses diet soda over regular soda and probably drinks at least one a day.
“I don’t like the syrupy taste of regular Coke, but I still get the caffeine without the calories,” she said.
But is Brown making a generally healthier choice by selecting a diet soda over a regular one?
According to a recent UNC study, diet soda probably isn’t much better for her health than regular soda if she has an unhealthy diet.
While previous research has linked drinking diet soda to poor health outcomes such as diabetes and cardiovascular disease, researcher Kiyah Duffy and others have noted that these past studies have not shown that drinking diet soda causes heart disease or diabetes; there may be other factors at play.
“What tends to matter is whether or not you’re eating well,” said Duffy, the lead researcher in the study, published in the American Journal of Clinical Nutrition. “If your diet is unhealthy, just drinking diet soda instead of regular soda might not help.”
Duffy and her colleagues at the UNC Gillings School of Global Public Health looked for other factors that might lead to the link between diet soda consumption and poor health outcomes.
They analyzed data that described the dietary habits of about 5,000 young adults and followed them over a 20-year period. The results of their study indicated that among people who ate a more healthful diet, those who also drank diet sodas had poorer health outcomes.
The researchers split the participants into two groups based on results from a baseline questionnaire about their diet habits. One group ate a more “prudent diet,” consisting of more fruits, nuts and vegetables and fewer snacks and fast food.
The other group ate a more “Western diet,” characterized by fewer fruits and vegetables and more snacks and fast food.
The researchers also split those groups into people who drank diet soda and those who did not during the month prior to the survey.
Eating a prudent diet and not consuming diet beverages were both independently associated with a lower risk of developing metabolic syndrome, a condition associated with heart disease and diabetes and characterized by high blood sugar, high waist circumference and high blood pressure.
However, because metabolic syndrome is defined by any combination of three or more risk factors, the interaction between overall eating habits and diet beverage consumption was not consistently correlated across all of the groups.
Overall, the researchers found that people who ate a prudent diet and did not consume diet beverages were least likely to develop metabolic syndrome. People at highest risk ate a Western diet and also consumed diet beverages.
“People think they’re doing themselves a favor by replacing sodas with diet sodas, but if they do that in the context of an otherwise unhealthy diet, it probably isn’t going to help if they’re still eating the fries and hamburgers,” said Duffy.
A deceptive term?
According to a 2012 Gallup Poll, 48 percent of Americans reported drinking at least one soda a day, though the report did not distinguish between diet and full-calorie sodas. While the term “diet soda” implies that it’s a more healthful option, that may not be the case.
Christina Munsell, a dietician at the Yale Rudd Center for Food Policy and Obesity, said she was not surprised by the findings of the UNC study.
“There’s no data that shows that switching to diet sodas is in any way, shape or form associated with weight loss and better health outcomes,” she said.
But research does not indicate that diet sodas are inherently unhealthy. Duffy and Munsell agree that there is not enough evidence to show that drinking diet sodas leads to poor health. Rather, they said, drinking diet sodas could be an indicator of other lifestyle factors that affect health.
“Diet soda is a reasonable substitute for regular soda for people like diabetics who are concerned with their blood sugar,” said Munsell. Even so, she questioned the need for so many sweetened beverages. “Artificial sweeteners are problematic as well, because it creates this expectation of sweetness.”
She pointed to the increase in marketing and availability of sweetened beverages.
“It’s become the norm to drink sweet drinks,” Munsell said, “the idea of drinking water has become boring. Sweet drinks are flashy; they’re always there. We evolved to crave that sweetness, so it’s kind of an exploitation of our natural desire for sweetness.”
Munsell said the good news is that people can wean themselves off sugar.
“If you can cut out sugar from your diet, you will crave it less,” she said. “Foods that might be only slightly sweet to heavy sugar consumers will taste very sweet to people who don’t regularly eat sugary foods.”
Back at Lenoir Dining Hall, students Malcolm Ogden and John Guzek said they’re perfectly happy with their water, even though it comes in smaller cups than the fountain drinks.
“Water’s really all you need,” said Guzek.
“It gets the job done,” added Ogden. “There’s no reason to add additives.”
Cover image Afroswede, flickr creative commons