In the black hole of bad news for diet soda lovers, there's a tiny glimmer of light.
The gloom set in when science showed drinking diet soda could lead to metabolic syndrome, a nasty mix of higher blood pressure and blood sugars that leads to weight gain and increases the risk of diabetes, heart disease and stroke.
But a new study has found that it's when you pair the common artificial sweetener sucralose with a carbohydrate — not the sweetener alone — that the body's metabolism changes in a way that can lead to metabolic syndrome.
Theoretically, that means you could enjoy a sucralose-sweetened diet soda without negatively changing your body's metabolism if you drank it all by itself — as long as it wasn't too close to eating a carb, of course.
"The question most people ask me is, 'Okay, so this means that I can have my diet soda if I drink it by itself, but how long do I have to wait?' We don't know that yet," said study author and neuropsychologist Dana Small, who directs the Modern Diet and Physiology Research Center at Yale University.
Now that your hopes are high, let's crash back into reality.
First, the study only looked at one artificial sweetener — sucralose. Around the world, the most common brands of sucralose are Splenda, Zerocal, Sukrana, SucraPlus, Candys, Cukren and Nevella.
There are dozens of other artificial sweeteners that might affect the metabolism differently.
"These results cannot be generalised to all sweeteners because the main types of different sweeteners commonly incorporated into our foods and drinks (including sucralose, aspartame, saccharin and Ace-K) are metabolised differently and therefore will have different health effects," said Sarah Berry in a statement by the UK's Science Media Centre. Berry is a senior lecturer of nutritional sciences at King's College in London and was not involved in the study.
Next, we really don't eat or drink our artificial sweeteners alone. They are baked into many of the snacks, sweets and processed products we devour daily.
Here's the really disturbing part of the study: Using sensitive brain scans, the researchers found that eating carbs and sucralose together changed the part of the brain that controls our metabolism in what appeared to be lasting ways.
"The regulator in the brain that controls how nutrients are being metabolized was changed, not only when the subjects are consuming the drink, but when they were just having another sweet thing or a salty and a savory thing," Small explained.
In other words, the brain was being trained to misinterpret sweetness.
"That was the significance," Small said. "It implies that it may not only be the sugar or the carbohydrate during the beverage that is being mishandled, but that carbohydrates they were consuming in other meals in the day that is also being mishandled."
The results happened so quickly — and so dramatically — that one arm of the study testing adolescents was stopped for ethical reasons.
"Adolescents have a period of natural and physiologic insulin resistance, which could change things and potentially make things worse for them," Small explained. "So we stopped the adolescent study and unblinded ourselves and took a look at the results."
At that time, only three adolescents had been exposed to the combination of carb and sweetener.
"All three of them had an increase in insulin insensitivity," Small said. "Two of them went from completely normal to within prediabetic range within that two weeks, suggesting that the effects were more pronounced in adolescence."
Much more research needs to be done, but be warned, soda lovers — there's a very real possibility that that glimmer of light in the dark will disappear.
"This research supports previous findings to suggest that we should not see diet drinks as a healthy alternative to sugar sweetened drinks," Berry said.
"Taken together with the evidence to support a detrimental effect of sugar on health, we should avoid excessive consumption of both sugar rich and artificial sweetened drinks and foods," she said. "Therefore, we should not be swapping diet drinks for full sugar drinks, but should be encouraging the consumption of water."