Do Sugar Substitutes Affect Gut Health? Here’s What Science Says

Key Takeaways

• Artificial sweeteners may affect more than taste perception: Research has explored how certain sweeteners interact with the gut microbiome.
• Different sweeteners may influence gut bacteria differently: Sucralose, saccharin, aspartame, and sugar alcohols are often studied separately.
• Research findings remain mixed: Studies on artificial sweeteners and gut health have produced varying results across populations and sweetener types.
• Digestive responses can vary by person: Some individuals report bloating, gas, or digestive discomfort with certain sweeteners or sugar alcohols.
• Overall dietary patterns still matter: Fiber intake, whole foods, and broader eating habits may also influence gut microbiome balance.

Added sugars are no friend to your health — especially your gut health. Eating too much sugar can trigger inflammation, increase your risk of developing leaky gut, and cause a potentially harmful microbial imbalance known as dysbiosis.

Due to these associated risks, swapping sugar for sugar substitutes may start to seem like an attractive option. Artificial and natural sweeteners have been marketed as healthier, lower-calorie alternatives to table sugar since the introduction of saccharin in 1970 and are recognized as safe by the U.S. Food and Drug Administration.

More people are turning to these sweeteners to replace some or all of the sugar in their diets. Annual sugar consumption in the U.S. has decreased by 25.4 pounds per person since 2000, while purchases of products that contain both traditional and alternative sweeteners have increased.

Today, 40% of adults and 25% of children consume these sweeteners regularly in products like diet soda, but some evidence suggests that the swap could have adverse effects on gut health.

Sugar Substitutes and Gut Bacteria Health

Part of the reason sugar substitutes are so attractive is that they offer a sweet flavor with a fraction of the calories of regular sugar. These sweeteners are divided into two categories based on calorie content:

• Non-nutritive sweeteners marketed as “zero calorie,” such as aspartame (NutraSweet, Equal), saccharin (Sweet’N Low), sucralose (Splenda), and stevia
• Nutritive sweeteners containing minimal calories per serving, such as xylitol, sorbitol, and mannitol

Up to 75% of the compounds in both types of sweeteners travel to your colon during digestion and may affect your gut microbiome.

Artificial Sweeteners and Gut Health

Artificial sweeteners are sugar alternatives created synthetically in a lab. The FDA currently authorizes six of them: aspartame, acesulfame-K, saccharin, sucralose, neotame, and advantame.

Despite their continued popularity in the food and beverage market, artificial sweeteners have been under scrutiny for their potentially harmful effects since 1968, when studies linked a sweetener called cyclamate to chronic disease. Since then, further research has suggested similar effects from other artificial sweeteners, but results from studies of their impact on gut health are mixed.

Some research suggests that consuming these sweeteners can lead to problems similar to those associated with sugar. In studies on rodents and humans, each sweetener has shown different potential effects:

• Aspartame may increase populations of pro-inflammatory or pathogenic bacteria, decrease beneficial microbes, and affect the variety of species within the microbiome.
• Saccharin may cause significant microbiome changes, including increased pro-inflammatory bacteria, even at low doses. It may also reduce populations of microbes that help regulate blood sugar and inflammation.
• Sucralose can alter the population of many different microbes, increase pro-inflammatory compounds, or damage the intestinal barrier. The effects may be more significant with long-term use.

Sometimes, though, study results don’t show any effects on the microbiome, inflammation, or metabolism, even at levels much higher than is possible to consume in your diet. In some studies, saccharin and sucralose have even been shown to increase the production of beneficial short-chain fatty acids (SCFAs).

The Gut Effects of Natural Sweeteners and Sugar Alcohols

Other sugar alternatives like stevia are seen as healthier and more natural than artificial sweeteners. However, these alternatives may actually be either natural or artificial because they can either be made from sources like fruit or plant roots or produced synthetically.

Regardless of which method is used, “natural” sweeteners may not work out better for your gut microbiome. Stevia, which comes from the leaves of the Stevia rebaudiana plant, appears to have some potentially beneficial properties. However, an extract of the sweetener called Rebaudioside A (Reb A) can reduce healthy bacteria in your gut and increase the production of compounds associated with body fat and obesity. Long-term stevia consumption may promote pro-inflammatory responses in your gut and liver.

Monk fruit is a newer addition to the family of alternative sweeteners. It’s made from the fruit of a plant called lo huan go and was approved by the FDA in 2010. Research on its effects on the gut is limited, but a study using microbes cultured in petri dishes showed that mogroside V, the main compound responsible for monk fruit’s sweetness, may support both beneficial bacteria and short-chain fatty acids (SCFAs). In theory, these effects could support gut health and help maintain healthy blood sugar responses.

Sugar alcohols, which include sweeteners like xylitol, sorbitol, and mannitol, may have some beneficial effects, including increased production of anti-inflammatory SCFAs and an overall increase in populations of beneficial bacteria. But using large amounts of these sweeteners may give you diarrhea because they aren’t fully broken down before reaching the colon.

Effects and Side Effects of Sugar Substitutes

The changes that sugar substitutes can cause in your microbiome may impact systems throughout your body and lead to other health effects, including:

• Slowing the movement of food in your digestive tract
• Affecting your body’s ability to use insulin
• Increasing your fasting blood sugar levels
• Interfering with some metabolic functions, which may lead to weight gain
• Changing how your body metabolizes carbohydrates and absorbs nutrients
• Increasing inflammation in and outside of the gut
• Altering the process your cells use to make energy, known as the Krebs cycle
• Increasing the expression of genes associated with bacterial toxins

In some people, artificial sweeteners may trigger more immediate symptoms like headaches, fatigue, and dizziness. One particular sugar alcohol, erythritol, has been linked to cardiovascular problems like heart attack and stroke. This may be due to its potential to increase the risk of blood clots, so the scientists who discovered the link recommended that more research should be done to evaluate the sweetener’s safety.

Better Sugar Alternatives for a Healthy Gut

If you want to cut back on sugar but don’t want to wait for scientists to determine which sugar substitutes are safest, you have several options that could potentially support gut health without causing side effects:

• Dates have a flavor similar to caramel and are available whole and in the form of unrefined sugar or syrup. Unlike sugar and other alternative sweeteners, dates provide fiber along with a range of nutrients and antioxidants.
• Sweet potatoes add moisture and sweetness to baked goods like cake and quick breads, and can actually feed your microbiome thanks to the 6 grams of fiber you get from one large sweet potato.
• Yacon syrup, made from the roots of the yacon plant, contains fructooligosaccharides, a type of fiber that may support your microbiome and improve digestion.

But don’t stop at switching up your sweeteners if you want better gut health! Other healthy dietary changes, such as increasing your intake of high-fiber fruits, vegetables, whole grains, and legumes, are also important for maintaining a healthy microbiome. Emphasizing these foods can improve the quality of your diet and lower your overall fat intake, two factors that appear to influence how your microbiome responds to sugar substitutes. So whether you choose to use alternative sweeteners or not, keeping your microbiome well-fed can help maintain a healthy gut even as you enjoy the occasional sweet treat. 

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