Myth or fact

Do artificial sweeteners spike your blood sugar?

Short answerNot the way you think

By GyroscopeUpdated November 14, 20266 sources

Not right away. Across 29 trials with 741 people, sweeteners like aspartame, saccharin, stevia and sucralose didn’t raise blood sugar. But in a 2-week trial of 120 healthy adults, saccharin and sucralose changed people’s gut bacteria and made their bodies handle sugar a little worse, and only in some of them.

Why do people think sweeteners spike blood sugar?

Two stories go around. One says your body tastes sweetness and releases insulin anyway, so a diet soda acts like a regular one. The other says sweeteners wreck your metabolism over time, pointing to studies where diet soda drinkers had more diabetes. Both have a grain of something real in them, and both get stretched.

A sweetener is like a key cut to fit the lock on your tongue. It sets off the taste of sugar, but it carries no sugar into your blood for insulin to move.

Do sweeteners raise blood sugar when you have them?

No. In 2018, researchers pooled 29 randomized trials with 741 people who were given aspartame, saccharin, stevia or sucralose and had their blood sugar measured. The sweeteners didn’t raise blood glucose.

That makes sense from the label. A 12-ounce can of regular cola has 39 grams of sugar, almost 10 teaspoons. On the glycemic index, soda scores 59 and table sugar 65. A diet cola has none of that sugar to turn into glucose.

Then what did the gut bacteria study find?

The open question is what happens over weeks. In 2022, researchers gave 120 healthy adults one of four sweeteners (saccharin, sucralose, aspartame or stevia) every day for 2 weeks, at doses below the official acceptable daily intake. Control groups got plain glucose or nothing.

All four sweeteners changed people’s gut bacteria. As groups, the people on saccharin and sucralose handled a glucose drink a little worse after 2 weeks. Within every group, some people changed a lot and others not at all.

Then the researchers went a step further. They took stool from the people who changed most and least and put it into germ-free mice. The mice largely copied their donors, so bacteria from a big responder gave the mice a worse glucose response too. That points to the gut bacteria as the way the sweeteners had their effect.

This fits a wider pattern. People’s blood sugar responses differ a lot, and in a 2015 study of 800 people in Israel, gut bacteria helped predict who would react to which meal.

What about diet soda and diabetes?

When researchers pooled 17 long-term studies, diet drinks went with 25% more type 2 diabetes per daily serving. After adjusting for bodyfat that fell to 8%, and the authors found signs that even the 8% was biased. One likely reason is that people who are gaining weight or already at risk switch to diet drinks. Sugary drinks went with 13% more diabetes after the same adjustment.

The best case against sweeteners

Nobody has run a long trial showing whether the gut changes add up to more diabetes over years. Until someone does, we’d use sweeteners as a step down from sugar on the way to water.

What should you drink, then?

Water, sparkling water, plain coffee and plain tea come first. If you’re coming off regular soda, diet soda is a fine bridge, and it removes the 39 grams of sugar a can that do raise your blood sugar. If you drink a lot of diet soda already, try cutting back to see if you miss it. And if you wear a sensor, a diet soda makes a nice test, since you’ll see no hill.