How that new infographic about drinking Diet Coke holds up to scientific scrutiny

WHAT SCIENCE SAYS: Aspartame definitely tastes sweet, but the body doesn't react to it the same way that it does to sugar.

THE EVIDENCE: A study published in the American Journal of Clinical Nutrition in 2005 examined the brains of five men after they consumed four different drinks. Each man drank water, a drink with sugar in it, a drink containing aspartame, and then a drink with carbohydrates that didn't taste sweet. After each drink, scientists measured their brain activity.

When the men drank the sugary drink, scientists saw a change in a region of the brain called the hypothalamus — but that change didn't occur for the other three drinks.

Consciously, you may think aspartame tastes like sugar, but your brain really can tell the difference.

WHAT SCIENCE SAYS: Stanhope told Tech Insider the claim that aspartame causes an increased insulin response is "absolutely without proof" to the best of her knowledge.

THE EVIDENCE: Stanhope ran a study that measured levels of insulin in people who drank diet beverages several times a day over multiple, 24-hour periods.

First, the subjects' normal insulin levels were measured. Then the scientists asked subjects to drink one large, aspartame-containing drink with breakfast, lunch, and dinner. After each meal, the scientists measured their insulin levels again — and the study ultmately found that drinking a diet soda had no measurable effect.

In addition, the aforementioned 2005 study (which measured the brain activity of people after they drank beverages containing sugar, aspartame, a carbohydrate, or just water) also found that drinking a diet soda didn't affect insulin levels.

WHAT SCIENCE SAYS: The studies cited in the infographic don't actually back up these claims.

THE EVIDENCE: A blog post by Naik, which accompanies the infographic, cites a few scientific studies. But those studies are observational and don't test an intervention — they only show an association between drinking diet soda and increased risk for negative health effects. They don't prove that drinking diet soda causes the risk.

"It's just as likely obesity causes people to drink aspartame," Stanhope told Tech Insider.

You have to look at studies that intervene and make people change their diets to really see what's the cause and what's the effect, Stanhope said. This kind of research indicates that regularly drinking sugary beverages does affect the body's fat reserves, cholesterol levels, weight, and blood pressure — and that drinking beverages containing aspartame does not.

WHAT SCIENCE SAYS: Drinking Diet Coke is not "potentially deadly" or even known to be harmful.

THE EVIDENCE: Dr. Michael Taffe, an addiction researcher at the Scripps Research Institute, told BuzzFeed that the amount of caffeine in a Coke "is not going to have very large functional effects in most people and particularly not those who consume caffeinated beverages somewhat frequently."

As for the research Naik cites about "excitotoxins": It's not about drinks containing aspartame. Instead, the study is about food that contains the neurotransmitter glutamate or substances similar to it. A comprehensive safety evaluation of aspartame reviewed studies about the substance's effects on the nervous system, and it didn't find evidence aspartame caused any ill effects.

You can drink many things more nutritious than diet soda. But claims based on scientific evidence need to be examined in context, keeping in mind what studies can actually prove — and what they can't.