Eating something sweetened with a sugar substitute won’t by itself cause your glucose levels to spike. That’s because these artificial sweeteners don’t actually contain glucose; they just stimulate your sweet receptors so you get the taste without the calories.
And while that sounds like a get-out-of-glucose-jail-free card, studies suggest these sweeteners can have metabolic consequences, influencing your body’s ability to process glucose and insulin over time, and even contributing to obesity.
The science on these substances is extensive, but complex and often contradictory. So let’s break down what we know and what you can do about it.
The Artificial Sweetener Universe
There are three categories of non-sugar sweeteners: artificial, natural and sugar alcohols. Artificial are the most familiar—as many as 40% of adults consume them—and the most studied. These include:
- Saccharin (Sweet ’N Low)
- Sucralose (Splenda)
- Aspartame (NutraSweet, Equal)
- Acesulfame Potassium, or Ace-K (Sweet One)
Natural sweeteners also provide taste without calories but are derived from plants or fruit. Stevia is the most prevalent, but you may also see monk fruit or yacon syrup.
Sugar alcohols like xylitol and erythritol are found naturally as well. Unlike the others, these have some calories, but no nutritional value, so they’re more sweetener than sugar.
Will Sweeteners Raise My Glucose or Insulin?
Although dumping a pack of Splenda in your coffee won’t immediately spike your blood sugar, researchers have identified a few ways they can have a metabolic effect on your body.
One has to do with your gut microbiome, that collection of bacteria, viruses and fungi in your stomach that helps process food. We know there are links between bacteria composition and conditions like obesity, insulin resistance and diabetes. And we know that artificial sweeteners can affect the gut’s makeup. In one study, mice fed saccharin, sucralose or aspartame for 11 weeks showed changes to the bacteria in their gut and elevated blood sugar. When researchers transferred the altered bacteria to other mice, those mice also developed high blood sugar.
The study suggested a similar effect in humans. Researchers found gut bacteria from people who ate a lot of sweetener looked different from people who didn’t. And when they transplanted that sweetener-modified human bacteria into mice, those mice developed high blood sugar. What we don’t know is the exact way that sweeteners change the microbiome, and if that change in fact causes metabolic conditions.
Another notion is that these artificial sweeteners break the association between sweet taste and caloric consequences—a connection our bodies have spent millennia developing. So, for example, when something sweet hits your tongue, your body releases insulin (known as a cephalic response). If an artificial sweetener triggered that response, your body then has no glucose to process, which could lead to excess insulin. The actual mechanisms at play are much more complicated—involving multiple signaling pathways and hormones—and researchers haven’t yet found the smoking-gun link to metabolic conditions.
A more recent idea revolves around the fact that we actually have sweet taste receptors in our gut. Research shows that sweeteners can trigger these receptors and cause the release of certain glucose-related hormones, but it’s so far not clear that this causes a change in blood sugar in humans.
What’s more, artificial sweeteners may unfavorably alter metabolic hormones. Research in rats has shown that artificial sweetener consumption can cause a decrease in the release of hormone GLP-1, which is involved in appetite regulation and blood sugar. When GLP-1 is low, it can promote increased food intake and high blood sugar, and over the long term, may increase the risk of diabetes and cardiovascular disease.
It’s also important to note that many studies in humans have shown increase in body weight associated with artificial sweetener use.
What About Natural Sweeteners?
Here’s some potential good news: Studies suggest stevia may not suffer these same drawbacks. In one, test subjects showed lower levels of glucose and insulin after a meal when they ate stevia first compared to people who ate sucrose or aspartame. Other research has even shown it can lower blood sugar in diabetics. (Though other studies disagree.) Similarly, sugar alcohols seem not to show negative metabolic effects—they can, however, cause digestive issues at high doses.
So… What Should I Do?
There is a lot of research tying sweeteners to negative outcomes, but also a lot of variables. One thing appears clear: sweeteners are not all created equal, and some may have real metabolic consequences, particularly the class of artificial sweeteners. Natural sweeteners like stevia and sugar alcohols like erythritol are likely the safer choices, but still may tap into our reward pathways that make us crave sweet foods.
If you’re using a continuous glucose monitor to track your blood sugar, you might not see an immediate glucose spike when you substitute artificial sweeteners for sugar, but there may be metabolic effects compounding under the surface, related to the microbiome or hormones like GLP-1, which affect glucose uptake. The safest route: avoid this category of sweeteners altogether.
Fortunately, research shows that cravings for sweet foods significantly decrease over time when you limit carbohydrates. What’s more, there may be certain naturally-sweet foods that don’t cause a significant glucose spike for you, and pairing sugary foods like fruit with protein, fat, fiber, or cinnamon can offset the glucose spike.