Does Diet Soda Affect Your Brain? What the Science Says

That crisp, bubbly sip of a diet soda can feel like a perfect afternoon pick-me-up or a satisfying mealtime companion. Since it contains zero sugar and zero calories, it seems like a harmless choice, especially compared to its sugary counterparts. But what does a daily habit of drinking this popular beverage mean for your long-term brain health?

The conversation about diet soda consumption and brain health often centers on artificial sweeteners. These are sugar substitutes used to sweeten foods and drinks without adding calories. While many are approved for consumption and generally considered safe, emerging research is taking a closer look at their long-term effects, particularly on the brain. “Artificial sweeteners are considered safe when used within recommended limits, but new research suggests they may influence brain health over time,” shares Jamie Lee McIntyre, RDN. A recent study observed that higher consumption of certain low- and no-calorie sweeteners (LNCSs) was associated with a faster rate of cognitive decline over an eight-year period. Although observational studies can’t prove a cause-and-effect relationship, this has led many to wonder about the popular sweetener in diet soda: aspartame. Let’s explore what science and experts have to say about how a daily diet soda could influence your brain.

Aspartame Can Affect Neurotransmitters

“One impact of drinking [diet soda] daily may have on your brain is related to aspartame metabolism,” says Luke Barr, M.D., a neurologist. “Aspartame breaks down into phenylalanine, aspartic acid and methanol, and phenylalanine in particular can alter neurotransmitter balance in the brain when consumed in high amounts. This disruption may affect mood regulation and cognitive clarity, especially in people who are sensitive to it.”

Neurotransmitters are chemical messengers that your brain cells use to communicate with each other. They impact everything from your mood and focus to your sleep cycles. When this delicate balance is disturbed, you might experience unfavorable effects when it comes to your brain health. While the amount of phenylalanine from a single diet soda is small for most people, a consistent, daily intake could have a cumulative effect over time.

Linked to Headaches and Migraines

If you’re prone to headaches, your daily diet soda might be a contributing factor. “Another impact is that frequent aspartame consumption has been linked in some studies to increased risk of headaches and migraines,” Barr says. “The mechanism is not fully understood, but it is thought that aspartame’s effect on neurotransmitters and vascular regulation in the brain may trigger these episodes in certain individuals.”

For those who are sensitive, the components of aspartame could potentially act as a trigger, initiating the painful cascade of a migraine or tension headache. While not everyone who drinks diet soda will experience this, it’s a potential connection to be aware of if you regularly suffer from headaches.

Impact on Cravings and Appetite Signals

Have you ever noticed that you crave more sweet things after having a diet soda? This might not be just in your head. “One possible impact of [diet soda] on the brain is its effect on appetite regulation—some studies suggest artificial sweeteners like aspartame or sucralose can disrupt the brain’s ability to link sweetness with calories, potentially influencing cravings and hunger signals,” notes McIntyre.

Your brain is wired to expect energy (calories) when it tastes something sweet. When you consume something intensely sweet but with no calories, it can disrupt this learned response. Over time, some suggest that this could potentially alter how your brain perceives sweetness and manages hunger, possibly leading to increased cravings for actual sugar.

It is important to note that not all data supports the notion that eating sweets causes a sweet tooth. One review study highlighted that while short-term exposure to sweetness often reduces the desire for it, long-term exposure has little to no consistent effect. Even in children and infants, there’s no clear link between eating sweet foods and developing a stronger preference for sweetness. Another review paper suggests that consumption of these sweeteners may not impact sweet cravings as well. Clearly, more data is needed before we can make a firm statement about this factor. 

Connection to the Gut-Brain Axis

The health of your gut and your brain are deeply connected through what is known as the gut-brain axis. This is a communication superhighway between your digestive system and your central nervous system. “Artificial sweeteners could influence gut microbes, and since our gut is closely tied to our brain, this might impact mood and cognitive function,” says Whitney Stuart, M.S., RDN.

How Other Artificial Sweeteners Impact Brain Health

Aspartame isn’t the only artificial sweetener on the market, and each one interacts with the body differently. Diet soda is sweetened solely with aspartame, while zero-sugar sodas contains both aspartame and acesulfame potassium (Ace-K).

“Other artificial sweeteners, such as sucralose or saccharin, have also been studied for their effects on the brain,” says Barr. “While their metabolic pathways differ from aspartame, some research suggests that they can alter gut microbiota, which in turn affects the gut-brain axis. This means they may indirectly influence mood, memory and even stress regulation, although the evidence is still evolving.”

Yet, a new study looked at how six different sweeteners affected gut bacteria. The researchers found that some sweeteners, like sucralose and Ace-K, were not significantly broken down in the gut and didn’t cause major changes to the microbial environment. This highlights that not all artificial sweeteners behave the same way in our bodies. Still, as Stuart points out, general research points to a “potential link between higher consumption of artificial sweeteners and faster cognitive decline, memory deficits and signs of neuroinflammation.”

Drinks That Support Brain Health

If you’re looking to swap your daily diet soda for something more brain-supportive, there are plenty of delicious and healthy options to choose from.

• Water: The simplest drink is sometimes the best. This drink is free from artificial sweeteners, and it is ultra hydrating. Infusing it with lemon, cucumber or mint can add a refreshing flavor.
• Green Tea: It contains caffeine for a gentle energy boost, and also L-theanine, an amino acid that promotes a state of calm alertness. It’s also packed with antioxidants that help protect brain cells from damage.
• Berry Smoothies: Berries are rich in flavonoids, which are compounds known to support memory and learning. Blending them with a base of water, milk or yogurt creates a nutrient-dense drink that’s great for your brain.
• Golden Milk: This warm, comforting drink is made with turmeric, a spice containing curcumin. Curcumin has powerful anti-inflammatory and antioxidant properties that may help protect long-term brain health. When made with cow’s milk, golden milk also offers essential nutrients, including iodine and choline, which are important for supporting healthy brain function.
• “Better-for-You” Sodas: There’s no shortage of soda options on the market these days, and many are made with more natural sweeteners (like stevia) and are free from artificial ingredients. While these should not be consumed in copious amounts, they can be a nice substitute for a diet soda if you are looking for something with a similar effervescence and flavor, sans the aspartame. 

Our Expert Take

So, is it safe to drink diet soda every day? “The occasional [diet soda] is unlikely to cause significant harm for most people, but a daily long-term habit could have cumulative effects, especially in those who are predisposed to headaches, mood disorders or who are highly sensitive to artificial additives,” explains Barr. “Balance and moderation remain key for brain health, and it’s always worth remembering that hydration from water and nutrient-rich diets are the strongest protectors of long-term cognitive function,” he adds.

Ultimately, the choice is yours. As McIntyre concludes, “While swapping [diet soda] for water or other unsweetened drinks is generally better for overall health, enjoying it now and then as part of a balanced diet is perfectly reasonable.” We’ll drink to that!