The Dark Truth About Diet Soda & Mental Health

Men, aspartame-sweetened diet sodas could be screwing with your swimmers. You know what I mean, your sperm. It’s a hard truth. Do you have the balls to hear it?

Men, aspartame-sweetened diet sodas could be screwing with your swimmers. You know what I mean, your sperm. It’s a hard truth. Do you have the balls to hear it?

I’m going to quickly hit you with some data, before we cuddle up with a broader point about interpreting animal model literature in an intellectually honest way.

If you prefer to watch, there’s now a video to accompany this letter:

Low-Dose Aspartame Causes Anxiety in Mice

The paper I want to spend a few minutes exposing you to was published in PNAS (say that out loud fast and you’ll get the irony). The researchers gave mice low-dose aspartame, the mouse-to-human adjusted equivalent of 2-4 small (8 oz) cans of aspartame-sweetened diet soda.

Exposure to aspartame caused anxiety in male and female mice over 12 weeks, as measured by validated behavioral tests like this open field test (OFT), where lower on the chart indicates more anxiety behavior.

The mechanism likely had to do with changes in levels of receptors for key neurotransmitters, glutamate and GABA, in the emotional center of the brain.

Now, I know what you’re thinking: “Wow, this research deeper goes than a prostate exam from an overenthusiastic urologist.” But we’re not even at the interesting part…

A Transgenerational Effect

Yes, there was a clear behavioral effect of low-dose aspartame and a reasonable biological explanation, i.e. messing with the balance of excitatory and inhibitory neurotransmission in the brain.

But the really terrifying thing was that this was transgenerationally inheritable. In other words, the offspring of these mice, and even the grandoffspring had signs of anxiety on validated behavioral testing, despite having never been exposed to aspartame. You can see that in the graph below, where – again – lower indicates more anxiety-like behavior.

What Data Do You Need to Make a Decision?

Take a minute to think about how profound that is: the aspartame equivalent of even just 2 - 4 diet sodas per day, and the little cans at that, can lead to increased anxiety in the offspring, the children. But, of course, the immediate retort is always, “but these are just animal data,” with the implication being that I – or others who talk about the potential dangers of chemicals like aspartame – are overreaching on the data are creating unnecessary fear. At least, that usually seems to be the accusation rendered by the diet soda defenders.

But now I want to ask you a question: What human data would be required to demonstrate, without a shadow of a doubt, that diet soda or other aspartame-consuming foodstuff causes transgenerational anxiety in human children and in grandchildren of the human aspartame user?

Well, you’d probably need a multigenerational randomized controlled trial where you take a large group of humans and randomize a subset to consume a specific aspartame containing foods and others to consume no aspartame. Then you’d need to follow them and their children and potentially their grandchildren for the next 50 to 60 years.

Guess what? This study will never be done.

So, in disregarding the animal data with the statement, “but prove this works in humans,” one overlooks practical limitations of the scientific method and creates an impossible barrier of proof.

To hammer home the point, imagine if we applied this same logic to smoking. If we dismissed all but the perceived to be “top-tier” human randomized controlled trial evidence—and waited for a 50-year randomized controlled trial—millions of people would die because no action would be taken while waiting for data that will probably never exist.

Sometimes, waiting for perfect proof isn’t wisdom—it’s willful ignorance.

Now, I’m not saying drinking diet soda is as bad as smoking. Because I know someone is going to go on an angry rant about this problematic equivalency. It’s an analogy, not an equivalency. But I think it’s a fair one. It’s simply emphasizing that data are often imperfect, and we need to make do with the data we can collect, which almost always has caveats. Then, given the imperfect data, we must make calculated decisions.

My Mental Calculus on Diet Soda

In this case, I’ll walk you through my own mental calculus: Diet soda may mess with my sperm and put my children at a higher risk of anxiety.

Do I know this will happen for sure? No.

But is there a chance? Yes.

So, I’ve identified the risk as an uncertain, but a potentially high-impact negative outcome. How about the reward? For me, zero. The cost to me of giving up diet soda is nothing. I think water is fine - sparkling if I’m in the mood for it. And even if I were I to want a diet soda, I know I could opt for one with an alternative sweetener, like stevia, or just add stevia, monk fruit or other sweetener I deem safer to a seltzer water.

So, the risk/benefit analysis to me makes it clear and I’ll probably never have another aspartame-sweetened diet soda as long as I live.

Otherwise put, if a drink might sabotage my sperm, I’m pulling out faster than… well, you get the idea.

Conclusion

Oh, and if you perchance wanted to hear the authors’ conclusions. Here’s an excerpt from the paper, “Extrapolation of the findings to humans suggests that aspartame consumption at doses below the FDA recommended maximum daily intake may produce neurobehavioral changes in aspartame-consuming individuals and their descendants. Thus, human population at risk of aspartame’s potential mental health effects may be larger than current expectations, which only include aspartame-consuming individuals.”

At the end of the day, this isn’t about fearmongering—it’s about understanding risk and making informed choices.

We may never get a perfect, long-term, multigenerational human study proving with absolute certainty that aspartame messes with our brains, our sperm, or our children’s mental health. But dismissing compelling animal data just because it’s not human data?

That’s not science—that’s denial.

So, here’s the question: What’s diet soda really worth to you?

You don’t have to agree with me, but at least be honest about the trade-offs. Because when it comes to something as important as your health—and possibly your future kids' health—waiting for perfect proof might just be the worst mistake you could make.

Recent Video On Aspartame