Recent studies link common sugar substitutes to heart trouble, memory decline, and stronger cravings

You swapped sugar for a zero-calorie sweetener because you wanted to protect your heart and you were concerned about weight gain. New research says that swap might be doing the opposite. As they say, “There’s no such thing as a free lunch.”

Millions of people reach for these products every day, whether they are managing diabetes, trying to lose weight, or protecting their teeth. The assumption has always been the same: no calories and no sugar means a safer choice. A wave of recent studies is asking whether that assumption still holds up.

A study presented at the European Society of Cardiology Congress in August 2026 followed more than 17,000 people across two long-running research groups, the Canadian Longitudinal Study on Aging and the European Prospective Investigation into Cancer in Norfolk, England. People with the highest blood levels of xylitol, a sugar alcohol used in sugar-free gum, candy, and baked goods, had a 57% higher risk of a major cardiovascular event in the six-year study group and an 18% higher risk in the group followed for thirty years.

The risk showed up regardless of age, weight, blood pressure, or diabetes status. Lead researcher Dr. Marco Witkowski of Charité University Hospital in Berlin said the findings show how little is actually known about the long-term safety of a sweetener found in thousands of everyday products.

That is not the only sugar substitute drawing scrutiny. Here is what the research says about the sweeteners sitting in your pantry right now, and what it might mean for your body and your mind.

What Sugar Substitutes Do to Your Heart

Xylitol is not the first sugar alcohol to raise concern. Erythritol, a sweetener found in many “keto” and “sugar-free” products, has been the subject of research out of the Cleveland Clinic for several years. A 2023 study published in Nature Medicine followed more than 4,000 people in the United States and Europe and found that those in the top 25% for blood erythritol levels were about twice as likely to have a heart attack or stroke within three years compared to those in the bottom 25%.

A follow-up study in 2024 helped explain why. Cardiologist Dr. Stanley Hazen and his team gave erythritol to healthy volunteers and watched their blood erythritol levels spike more than 1,000 times above normal. Their blood platelets, the cells responsible for clotting, became noticeably more likely to clump together and form clots. Plain sugar didn’t have this effect. Dr. Hazen said that for people already at risk for blood clots, choosing an occasional sugar-sweetened treat may be the safer option compared to regularly reaching for foods and drinks sweetened with sugar alcohols.

These are not obscure ingredients. Xylitol and erythritol show up in sugar-free gum, protein bars, diet sodas, and a long list of “no added sugar” baked goods. Reading past the front label to the ingredient list is the only way to know which sweetener you are actually consuming.

The Toll on Your Brain and Mood

The concerns do not stop at the heart. A study published in the journal Neurology in 2025 followed nearly 12,800 adults in Brazil for about eight years, tracking their memory and thinking skills alongside their intake of seven common sweeteners, including aspartame, saccharin, and xylitol. People who consumed the most saw their thinking and memory skills decline 63% faster than people who consumed the least, a difference researchers compared to roughly 1.6 years of extra brain aging.

The link was strongest in adults under 60 and in people with diabetes. Interestingly, one sweetener in the group, tagatose, showed no connection to faster decline at all. Harvard Health Publishing, reviewing the same research, noted that the pattern held up even after researchers accounted for other health and lifestyle factors.

Sweeteners appear to affect more than memory. A 2025 study out of the University of Southern California and University Hospital Tübingen used brain scans to watch what happens when people drink water sweetened with sucralose, the sweetener sold as Splenda. Sucralose activated the hypothalamus, the part of the brain that governs hunger, and increased participants’ reported hunger by about 17%, an effect that was strongest in people with obesity.

Blood tests showed sucralose did not raise any of the hormones that normally signal fullness. In other words, the brain believed it was still hungry even though no calories had been consumed. Researchers also found stronger connections between the hunger center and the part of the brain that weighs risk and reward, suggesting the sweetener may make it harder to resist the next craving.

That combination, a brain that feels hungrier without a body that needs food, is a recipe for the frustration and loss of control many people already feel around food and weight. Clinicians who work with patients on eating habits see this pattern often. A craving that will not quiet down, followed by guilt over giving in to it, can wear on a person’s mood over time even when no single food choice seems like a big deal in the moment.

Why This Happens, and What to Choose Instead

Part of the explanation may sit in the gut. Research out of the Weizmann Institute in Israel, published in Nature, found that calorie-free sweeteners can change the makeup of gut bacteria in ways that affect how the body handles blood sugar. Gut bacteria also influence inflammation and energy levels throughout the body, which may be one thread connecting sweeteners to the wider effects researchers keep finding.

None of this means every sweetener belongs on a watch list. The Mayo Clinic points out that sugar substitutes are approved by the FDA, do not raise blood sugar, and can be useful for short-term weight management or reducing tooth decay. The concerns tend to center on regular, long-term, high-dose use rather than the occasional diet soda. Mayo Clinic researchers also note that sugar alcohols like xylitol and erythritol are more likely than other sweeteners to cause bloating, gas, and digestive upset, and they are not recommended for children under two.

If you are looking for a lower-risk option, monk fruit may be worth a look. The sweetener comes from mogrosides, natural compounds in a small fruit grown in southern China, and it carries no calories and no reported side effects. The Cleveland Clinic notes that monk fruit has been used safely for centuries and has a clean safety record so far, though it is still new enough to the American market that long-term studies are limited. One caution worth remembering: many products labeled “monk fruit sweetener” are actually blended with erythritol, so the ingredient list is still worth a close read.

The bigger picture is simple. Sugar substitutes were built to solve one problem, extra calories and blood sugar spikes, and for that narrow purpose, they still work. What the last few years of research make clear is that “calorie-free” was never the same thing as “risk-free.” Your heart, your memory, and your relationship with food all seem to be paying attention to what you are sweetening your coffee with, even when the label says zero.

What are researchers suggesting we do? The most useful step is not panic. It’s moderation, label reading, and a willingness to let a little real sugar back into your life now and then. Check the ingredient list before you check the calorie count. Rotate which sweetener you use instead of relying on one every single day. And if a product leans on erythritol or xylitol as its main sweetener, treat it the way you would treat dessert: fine once in a while, not something to build a daily habit around. Your heart and your brain may both thank you for it.