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Home » Diet soda has a bad reputation, but science disagrees

Diet soda has a bad reputation, but science disagrees

I love my diet soda, specifically one brand, but I kept reading that this was a bad habit that was going to kill me. I should be drinking water for my long-term health, getting rid of that sugar-free brown sparkling water forever.

I thought that I was taking a risk on my overall health by drinking diet soda even though it was better than drinking the full-sugar versions of that drink. But recently, I thought to myself, “self, is there any science behind the tropes about diet soda?”

I decided to dig into it, and what I figured out was that the science didn’t support the claims of the diet soda deniers. Not even close.

Now, I could stop here and call it a day, but I know my audience, and you want science supporting or debunking the claims of the anti-diet soda world. So, here I go with some science.

Photo by Matt Seymour on Unsplash

Who is opposed to diet soda?

Here’s the thing, a lot of organizations that seem to be concerned about nutrition advice have bad things to say about diet soda. There were so many organizations that repeated the same things about the zero-calorie drinks, I almost became convinced that I was wrong, and that I was going to quit cold turkey.

There were so many similar claims that I honestly got bored repeatedly reading the same conclusions. Here are some of them:

At this point, you’d think those diet sodas are the worst thing you could consume.

The American Heart Association guidelines include this statement:

…fostering a taste preference for sweet foods and beverages, making naturally sweetened foods less appealing, adversely altering feelings of hunger and fullness, reducing awareness of calorie intake, adversely altering gut microbiota, increasing glucose intolerance, substituting for healthier beverages, contributing to the perception that individuals can consume more calories from other foods, and contributing to the possible intake of other ingredients in LCS beverages that could be of concern such as caffeine and artificial colors.

At this point, you’d think those diet sodas are the worst thing you could consume.

Photo by Mathilde Langevin on Unsplash

The science

With all of these claims, you’d think that there’s some science behind it. The problem is that there is no science to back most of these claims or there is any scientific research that disputes their claims.

Let’s take a look at artificial sweeteners. There are a lot of false claims about artificial sweeteners that make no sense.

  • Sucralose (found in Splenda). I’ve reviewed sucralose before, and there’s not much there. The Food and Drug Administration has determined that the Acceptable Daily Intake (which it derives by determining the safe level and dividing by 100) is 5 milligrams per kilogram of body weight. If you weigh 150 pounds, that means you can eat 340 milligrams, the amount in 28 packets of Splenda, every day. That’s a lot of sucralose packets that you could consume before it had even a theoretical negative effect.
  • Aspartame (found in Equal). It’s the same thing, there are a lot of claims about it, but its safety is outstanding. Despite the lack of evidence of its safety, some companies have removed it from their drinks.
  • Artificial sweeteners and obesity. No evidence.
  • Artificial sweeteners and gut biome. The gut microbiome has become the conspiracy theory of nutrition — it is the claim that is made to prove that something is dangerous despite the utter lack of evidence. Almost all of the research on artificial sweeteners and the gut biome was on mice and rats. And as I have written many times, preclinical studies on rodents rarely, less than 1% of the time, lead to human clinical information. And if you take a bunch of mice or rats that are genetically similar, make sure they have no gut bacteria at the start of the study, and feed them different things, like artificial sweeteners, you will get dramatic results because there is no “noise” from the gut. In a living human gut, the biome is very complex, and a change in it would have to be powerful to show meaningful data.
  • Glucose intolerance. Once again, the lack of evidence in human clinical studies is remarkably lacking. The belief that artificial sweeteners induce glucose intolerance is based on the same thing we just discussed — the infamous gut biome.
Photo by Robert Anderson on Unsplash

More science

For regular readers of this blog, you know I give much more weight to meta-analyses and systematic reviews, so I found one that might work. In a meta-analysis published in January 2019 in the BMJ, researchers examined possible links between artificial sweeteners and various health outcomes.

They really couldn’t find any links between artificial sweeteners and negative health outcomes. They found small decreases in weight and blood glucose in those who consumed artificial sweeteners, although most of that data was from low-quality studies.

The authors concluded:

Most health outcomes did not seem to have differences between the NSS (non-sugar sweetener) exposed and unexposed groups. Of the few studies identified for each outcome, most had few participants, were of short duration, and their methodological and reporting quality was limited; therefore, confidence in the reported results is limited.

On the other hand, there is could clinical evidence that people will consume fewer calories overall when they consume low-calorie sodas instead of sugar-filled sodas. And there is also evidence that many will lose some weight, and some may lose a significant amount of weight.


As much as I looked, I could not find a bit of convincing, human clinical evidence that drinking a diet soda was dangerous. And as I wrote, there is convincing evidence that it might help. Outside of bariatric surgery and a few new and expensive drugs, is there anything else that has even moderate success in managing weight?

Maybe these health authorities should embrace low-calorie sweeteners and drinks. They should encourage people to switch from high-calorie, sugar-filled drinks to diet drinks for weight loss rather than inventing the non-existent adverse effects of artificial sweeteners. It seems like a good strategy.

But for those of you who have decided to use artificial sweeteners, the science seems to support the safety of these drinks. And there may be a benefit, especially to those who are fighting weight issues.

There’s one more thing — why do these health agencies that make nutrition recommendations use unscientific tropes for recommendations? There is much more evidence that my diet soda is going to help me than harm. The evidence is way over on the side of benefits with almost nothing supporting any risk.

The science is clear. If you have a diet soda in your hand, go ahead and drink it. Your gut biome isn’t going to care.


Michael Simpson

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