When we set out to see if diet soda is somehow better for you than regular soda, we quickly realized that the question was sort of like asking which brand of cigarette is best for distance runners, or whether death by impaling is preferable to being crushed by a falling piano. There may be subtle differences, but you go into the decision knowing both options are pretty lousy. “I like to reject the question outright,” says Susie Swithers, a neurobiologist and professor of psychological sciences at Purdue. “No one should drink a soda every day.”
Yes, if you down a daily diet soda (don’t feel bad, one in five of us do), that might be better than regular, in much the same way that if you’re going to eat four pizzas, it’s best to stick with the Veggie Lover’s. Mathematically speaking, zero calories is less than the 140 found in regular sodas. “But if you look at the long-term outcomes of people who consume diet versus regular against people who don’t drink soda at all,” Swithers says, “soda drinkers end up with way worse outcomes.” For instance!
• This study found that people who drank diet soda every day had a 61 percent higher risk of “blood vessel diseases,” such as stroke and heart attack, than those who drank none at all.
• And this one showed that older people who drank diet soda over nine years picked up about triple the waist circumference and belly fat as their non-soda counterparts. (That’s the body circumference you least want to increase.)
• Overweight or obese people who drink diet sodas eat significantly more calories.
• Oh, and people who drink diet sodas are more apt to eat like crap.
• Diet soda tastes like aluminum foil. We have no science for that, but we stand by it.
In many ways, we’ve come to associate “diet soda” with “health” in the same way we equate Lenny Kravitz with music—after a while, we just stopped thinking about it critically and got used to it. And yet, through decades of relentless marketing, we’ve come to believe can-sized servings of sugar can be consumed on the daily. “No adult would say, ‘It’s cool for me to have a bag of Skittles every day,’ ” Swithers reminds us, “but with sodas you go, ‘I should have that with my dinner.’ That’s effectively what soda is—candy in a can.”
There are three main problem groups here. First: Fake sweeteners like the ones in some diet sodas are up to hundreds of times sweeter than sugar, which gets your system used to synthetically sweet foods. Second: Our bodies are trained to associate “sweet” with “calories.” When you start untying that connection, it throws the system out of whack and might actually increase the craving for real sugar, since you technically haven’t gotten your fix yet. Third: It now seems possible, just possible, that drinking a stew of chemicals—including phosphoric acid (which leeches calcium from the bones), aspartame (which we convert into formaldehyde), sodium benzoate (that’s bad), and two coloring compounds that start with “methyl-”—is not altogether awesome for you.
So while diet soda may, in some twisted sense, be “better” for you than regular sugar-sweetened soda, Swithers reframes the question: “Why do you think soda is a good idea?”