An article titled “10 reasons to give up diet soda” has made its way around the web in the last few months, most recently to CNN this week. Below I reproduce each of their reasons and explain why it is scientifically misleading.
It confuses your body
Artificial sweeteners have more intense flavor than real sugar, so over time products like diet soda dull our senses to naturally sweet foods like fruit, says Brooke Alpert, author of “The Sugar Detox.” Even more troubling, these sugar stand-ins have been shown to have the same effect on your body as sugar. “Artificial sweeteners trigger insulin, which sends your body into fat storage mode and leads to weight gain,” Alpert says.
The theory that artificial sweeteners confuse the body is highly controversial in humans, but to claim it “dulls our senses to naturally sweet foods like fruit” is not something that can be done with any certainty. According to one study, people who drink diet soda (self-reported) had higher responses in several reward-related brain areas in an fMRI to saccharine. However this may be because people who naturally have a higher reward to sweetness consume more diet soda to begin with. The study also found a correlation between lower activation in a particular reward area with higher diet soda consumption, and the authors hypothesize that diet soda reduces dopamine release here, perhaps causing people to seek out more reward to satisfy this. This study did not account for other sweeteners in the diet, or address potential changes prospectively, and without further study tying this to actual calorie intake it is tenous. Moreover, another study recently showed that an artificially sweetened beverage in place of a sugar sweetened one did not change short-term reward value in the same brain region (also with fMRI), suggesting that maybe there isn’t really much real-world concern. In other words, diet drinks do not confuse the body’s learned response to sugar’s sweetness and calorie content. To add to this, the best randomized trial we have on diet beverages that consisted of consuming diet drinks or water for 6 months did not change the preference for sweet foods and beverages compared to water (in fact dessert intake was lower in the diet beverage group). This trial also found that the diet beverage group has a twice greater chance of achieving a 5% weight loss than a control group. While we are a long way away from a clear picture in this area, it seems unlikely that diet drinks would lead to a negative change in the diet.
Regarding artificial sweeteners and insulin, it is simply disingenuous. Sucralose doesn’t stimulate insulin, nor does sucralose or acesulfame potassium independent or together. Sucralose, acesulfame potassium, or aspartame also didn’t increase GLP-1 (which stimulates insulin secretion) in a separate study. Aspartame also didn’t increase insulin here, here or here (also saccharin). Peak insulin was no different after aspartame or saccharin in this one, though AUC was higher after aspartame but this was likely just noise as the authors state that it is “unlikely to be physiologically relevant”. One study did suggest that sucralose and acesulfame potassium together with 75 grams of glucose compared to carbonated water and glucose increases GLP-1, but insulin wasn’t changed. Here is a review on the topic that reaffirms the consistency of the research showing no effect on insulin.
It could lead to weight gain, not weight loss
Diet soda is calorie-free, but it won’t necessarily help you lose weight. Researchers from the University of Texas found that over the course of about a decade, diet soda drinkers had a 70% greater increase in waist circumference compared with non-drinkers.
And get this: participants who slurped down two or more sodas a day experienced a 500% greater increase. The way artificial sweeteners confuse the body may play a part, but another reason might be psychological, says Minnesota-based dietitian Cassie Bjork. When you know you’re not consuming any liquid calories, it might be easier to justify that double cheeseburger or extra slice of pizza.
This information is from a conference presentation in 2011, still not published today. So we can’t examine the study methods, limitations, and nuances. For example, based on the press release, it seems there was no statistical adjustment for dietary variables. More importantly, the overall evidence thus far (which I discussed here) suggests artificial sweeteners are associated with a slight reduction in weight loss when substituted for sugar. It is strange that the author would choose a study that s/he could not read over the many already published.
Regarding confusing the body, see the response to the previous claim. The data suggest that diet drinks do not lead to weight gain and probably assist a bit with weight loss when substituted for sugar.
It’s associated with an increased risk of type 2 diabetes
Drinking one diet soda a day was associated with a 36% increased risk of metabolic syndrome and diabetes in a University of Minnesota study. Metabolic syndrome describes a cluster of conditions (including high blood pressure, elevated glucose levels, raised cholesterol, and large waist circumference) that put people at high risk for heart disease,stroke, and diabetes, Bjork explains.
I also discussed the metabolic syndrome studies in the aforementioned post. They all caution about the potential for diet soda to be a marker for poor diet/lifestyle, and thus if any potential confounding dietary or lifestyle variables are not captured we risk an inaccurate result. We also don’t know from this particular study if reverse causation is a factor, as other research finds that diabetics consume more diet soda than non, which might be from them switching to diet soda and not the diet soda promoting disease. It was just used a food frequency questionnaire at baseline, which was correlated with future disease. I wrote about other studies on diabetes and metabolic syndrome before, which overall tend to suggest no association from the best research designs. Yet none of these were mentioned in the Health article.
It has no nutritional value
When you drink diet soda, you’re not taking in any calories — but you’re also not swallowing anything that does your body any good, either. The best no-calorie beverage? Plain old water, says Bjork. “Water is essential for many of our bodily processes, so replacing it with diet soda is a negative thing,” she says. If it’s the fizziness you crave, try sparkling water.
Carefully reading the literature suggests diet soda is likely as benign as water and is almost all water anyway.
Its sweetener is linked to headaches
Early studies on aspartame and anecdotal evidence suggests that this artificial sweetener may trigger headaches in some people. “I have several clients who used to suffer from migraines and pinpointed their cause to diet soda,” Bjork says.
She only cites one study with a weak design, and it is important to have placebo-controlled trials to determine if aspartame really causes headaches. According to a recent review of all aspartame research, the European Food Safety Authority concluded that “There is no convincing evidence that consuming aspartame causes headaches.” Perhaps spreading this rumor triggers headaches in some people because they think it does. Or maybe it really does cause them in certain people for reasons yet unknown- but this would be very rare.
It’ll ruin your smile over time
Excessive soda drinking could leave you looking like a “Breaking Bad” extra, according to a case study published in the journal General Dentistry. The research compared the mouths of a cocaine user, a methamphetamine user, and a habitual diet-soda drinker, and found the same level of tooth erosion in each of them. The culprit here is citric acid, which weakens and destroys tooth enamel over time.
This case study was about a woman who consumed 2 liters of diet soda (over 8 cans) per day for 3-5 years without seeking dental services for over 2 decades. It also notes some of the damage was due to junk food. In any case, not all soda contains citric acid, and citric acid is high in some fruits and fruit juices. In fact, according to unpublished data from here, diet sodas are lower than most fruit juices. Drinking 2 liters per day of either is obviously not a good idea.
It makes drinking more dangerous
Using diet soda as a low-calorie cocktail mixer has the dangerous effect of getting you drunk faster than sugar-sweetened beverages, according to research from Northern Kentucky University. The study revealed that participants who consumed cocktails mixed with diet drinks had a higher breath alcohol concentration than those who drank alcohol blended with sugared beverages. The researchers believe this is because our bloodstream is able to absorb artificial sweetener more quickly than sugar.
This is misleading. The study compared an alcoholic drink mixed with a diet soda or regular (sugary) soda and interestingly found a fairly large difference in peak blood alcohol level, which was higher when using diet soda through 3 hours.
Caveats: there were only 16 participants and they were required to fast 2 hours before drinking the beverage. There could have been substantial variation in food consumed before those 2 hours between the participants. However this makes sense in context to previous research: calories limit the peak blood alcohol level. It is not that diet soda per se makes drinking more dangerous, but that drinking on an empty stomach may make drinking more dangerous.
It’s associated with depression
A recent study presented at a the American Academy of Neurology meeting found that over the course of 10 years, people who drank more than four cups or cans of soda a day were 30% more likely to develop depression than those who steered clear of sugary drinks. The correlation held true for both regular and diet drinks, but researchers were sure to note that the risk appeared to be greater for those who primarily drank diet sodas and fruit punches. Although this type of study can’t prove cause and effect, its findings are worth considering.
Another study that isn’t published yet- we only know a few details from a press release. I am not able to find any published research on diet soda and depression. We should never draw conclusions based on single studies- especially epidemiological studies- and reporting this without serious caveats, else we unnecessarily scare the public.
It may be bad for your bones
Women over 60 are already at a greater risk for osteoporosis than men, and Tufts University researchers found that drinking soda, including diet soda, compounds the problem. They discovered that female cola drinkers had nearly 4% lower bone mineral density in their hips than women who didn’t drink soda. The research even controlled for the participants’ calcium and vitamin D intake. Additionally, a 2006 study published in the American Journal of Clinical Nutrition found that cola intake (all kinds, not just diet) was associated with low bone-mineral density in women.
This is strange because the 2 studies that are described here are one in the same. This epidemiological study also used food frequency questionnaires, but did confirm what other association studies have found: cola and reduced bone mineral density in females but not males. There isn’t a clear reason why this might be: the authors speculate that perhaps part of the reason is that cola consumption displaces calcium sources and caffeine may have an effect. It is notable that this result was found only for colas, and not other soda. Is it a real effect? We need more research, ideally a long-term trial to know for sure.
It may hurt your heart
Just one diet soft drink a day could boost your risk of having a vascular event such as stroke, heart attack, or vascular death, according to researchers from the University of Miami and Columbia University. Their study found that diet soda devotees were 43% more likely to have experienced a vascular event than those who drank none. Regular soda drinkers did not appear to have an increased risk of vascular events. Researchers say more studies need to be conducted before definitive conclusions can be made about diet soda’s effects on health.
I wrote about this study here. It has a small number of participants and cardiovascular events, and soda intake was only assessed one time at baseline. Meanwhile, other studies have found no association between diet soda and cardiovascular problems. Funny they just cherry pick one.