Which low-calorie sweeteners are safe—and which aren't?
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In this article recently published in our March 2023 print issue, we had reported that erythritol is a safe low-calorie sweetener. However, after we went to press, a new study found that it may raise the risk of blood clots. This version of the article has been updated to reflect the new study's findings.
Until we know more, limit your intake of erythritol (in sweeteners as well as some low-sugar ice creams, desserts, bars, drinks, etc.). Stay tuned for more on erythritol in an upcoming issue.
As people cut back on added sugars, low-calorie sweeteners are stepping in. They add sweetness with few or no calories to sodas and sports drinks, yogurts and ice creams, cookies and candy, toothpaste, and more.
Are they safe? It depends on the sweetener. Here are some key findings on the most popular ones.
Click on a link to jump to a specific section:
- Monk fruit extract
- Stevia extract
- Sugar alcohols
- Acesulfame potassium
- What to do
Allulose is a sugar that occurs naturally in small amounts in foods like wheat, maple syrup, brown sugar, and some fruits. Gram for gram, it’s about 70 percent as sweet as table sugar. But it has only a tenth of sugar’s calories because, unlike sugar, which is broken down by the body (releasing calories), allulose is excreted mostly intact.
In a study funded by the dairy industry, people rated allulose-sweetened nonfat Greek vanilla yogurt as favorably as yogurt sweetened with table sugar. They also reported less aftertaste from yogurt sweetened with allulose than with stevia or sucralose.
The primary concern: Allulose can cause trouble in the gut. When researchers fed increasing doses to 29 people, about a third had diarrhea, bloating, or abdominal pain after consuming a single high dose—roughly 35 grams for a 150-pound person. They had no symptoms at 27 grams. (For reference, a cup of Magic Spoon Fruity cereal has 10 grams of allulose.)
But that’s just one tiny study. Some people may be more (or less) sensitive. And no one has tested allulose on children or people with irritable bowel syndrome or other GI problems.
In 2019, the Center for Science in the Public Interest (Nutrition Action’s publisher) asked the FDA to require that food labels warn consumers that “excess consumption of allulose may cause diarrhea or other adverse gastrointestinal effects.”
Allulose is safe, but it may cause GI woes in sensitive people.
Sucralose, one of the most common low-calorie sweeteners, caused leukemia and other blood cancers in mice that were exposed to it from when they were fetuses to when they died.
And a handful of studies suggest (though others don’t) that sucralose may raise blood sugar by altering the gut microbiome.
In the best human study, researchers randomly assigned 60 healthy adults who didn’t regularly ingest low-calorie sweeteners to consume no sweeteners, 5 grams a day of glucose (a sugar), or a hefty 6 packets a day of sucralose (each with just under 1 gram of glucose for bulk). (The participants knew which one they were getting.)
After two weeks, the sucralose group was less glucose tolerant (less efficient in moving glucose out of their blood) than the other two groups. And when stool samples of the four top sucralose “responders” were implanted in mice with no gut bacteria, the mice had worse glucose tolerance (so the changes in the responders’ microbiomes must have been to blame).
Sucralose caused cancer in mice and may boost blood sugar. More studies are needed.
Monk fruit extract
Monk fruit has been used for centuries in Chinese medicine as a cough suppressant.
Monk fruit extract is about 200 times sweeter than table sugar. It’s made by extracting sweet (but calorie-free) compounds called mogrosides from the fruit.
Monk fruit makers consider the extract to be “generally recognized as safe,” and the FDA hasn’t objected. That means it can be used without prior FDA approval. But in 2019, the FDA’s European counterpart (the European Food Safety Authority) decided that it had too little evidence to determine if monk fruit extract was safe. It doesn’t cause gene mutations or alter development in animals, but unlike most other sweeteners, no long-term studies have tested whether it causes cancer in animals or alters blood sugar in people.
Monk fruit extract appears to be safe, but more research is needed.
Stevia, a plant native to South America, contains calorie-free compounds called steviol glycosides that are responsible for its sweetness. Four of the glycosides that are commonly extracted from the plant—stevioside, rebaudioside A (also called reb A or rebiana), reb D, and reb M—are 200 to 300 times sweeter than table sugar.
Stevia is often mixed with other sweeteners to mask its bitter aftertaste, though suppliers like ADM and Cargill claim that they have minimized any off-flavors.
Stevia is one of the safest low-calorie sweeteners. Rats fed high doses do not have a higher risk of tumors. While some test-tube studies suggest that stevia may increase the risk of genetic mutations (which could increase cancer risk), a European Food Safety Authority panel concluded in 2010 that stevioside and reb A don’t cause genetic mutations or cancer.
Stevia is a safe choice.
Sugar alcohols are neither sugar nor booze, but carbohydrates called polyols. (That’s the “P” in the low-FODMAP diet.) Sugar alcohols—which include erythritol, maltitol, mannitol, sorbitol, and xylitol—occur naturally in foods like mushrooms, pineapple, apples, and prunes.
Erythritol made headlines in late February when researchers reported that the sweetener—which we had considered safe—may raise the risk of blood clots. Until we know more, limit your intake of erythritol, which can be found in many sweeteners like Swerve (see photo), as well as in some low-sugar ice creams, desserts, bars, drinks, etc. (Stay tuned for more on erythritol in an upcoming issue.)
Erythritol clocks in at roughly 70 percent of the sweetness of table sugar but only 5 percent of the calories. Other sugar alcohols have about 50 percent of table sugar’s calories, which may be why they’re less popular with food companies.
Sugar alcohols (other than erythritol) remain largely unabsorbed as they travel through the GI tract, so they end up in the colon. There they can cause discomfort by drawing water into the gut, leading to diarrhea. And some are fermented by gut bacteria, causing gas or bloating.
But most people don’t need to steer clear of sugar alcohols entirely. The GI effects typically occur at higher doses, and they’re worse in people with irritable bowel syndrome.
(Food companies aren’t required to list the grams of sugar alcohols in a serving on the Nutrition Facts label, but many do. Check labels and ingredient lists if you think you’re sensitive.)
Got a dog? Xylitol—which can show up in chewing gum, baked goods, candy, mints, supplements, and more—may cause a rapid drop in blood sugar, liver damage, or even death if the pupper ingests it and isn’t treated quickly. (Cats aren’t sensitive to xylitol.)
Erythritol aside, sugar alcohols are safe but may cause diarrhea or gas, depending on the dose and your sensitivity.
Aspartame, which is used most often in drinks like Diet Coke and Diet Pepsi, is the low-calorie sweetener most rigorously studied for its potential to cause cancer.
The verdict isn’t good. In three large studies, researchers fed rats and mice varying doses of aspartame for their entire lives. The sweetener caused liver and lung cancer in male mice and leukemia and lymphoma in both male and female rats. (Those studies were larger and longer than the industry studies that the FDA relied on to approve aspartame.)
What’s more, in a study that followed roughly 125,000 adults for up to 20 years starting around the time aspartame entered the food supply, men (but not women) who reported drinking at least one diet soda a day had a slightly higher risk of multiple myeloma and non-Hodgkin lymphoma than men who drank no diet soda.
Given the troubling animal and human data, CSPI has urged the International Agency for Research on Cancer to review the evidence on aspartame. The agency plans to begin this summer. Stay tuned.
Current evidence indicates that aspartame causes cancer.
Acesulfame potassium, or Ace-K (“K” is the chemical symbol for potassium) is commonly used in diet drinks. It’s typically mixed with sucralose or aspartame.
Two rat studies suggest that Ace-K causes cancer. But like many other studies on the sweetener, they were poorly done.
And in a study of 34 breastfeeding mothers who drank a 12 oz. Diet Rite Cola (which contains 41 milligrams of Ace-K and 68 mg of sucralose), peak breast milk Ace-K levels were over 100-fold higher than peak sucralose levels over the next six hours. Other studies agree.
More research is needed to understand how acesulfame potassium in breast milk might affect an infant’s gut microbiome, growth, or development, or if Ace-K in breast milk leads to a preference for sweet foods.
Acesulfame potassium may increase cancer risk. And if you’re breastfeeding, play it safe and skip Ace-K.
What to do
The healthiest drinks are water (still or sparkling, flavored or not), unsweetened coffee or tea, low-fat dairy milk, and healthy plant milks.
But if you drink sugary beverages, it may be tough to switch from, say, regular Coca-Cola to seltzer. If so, you’re better off with diet drinks than with their sugar-heavy cousins.
Foods and drinks sweetened with stevia or monk fruit are your safest bets. Allulose and sugar alcohols are also safe, though they may cause GI symptoms. Exception: Erythritol's safety is now uncertain, so limit your intake until we know more. Also keep in mind:
Don’t give low-cal sweeteners to kids. They haven’t been tested in children.
There’s no good evidence that low-calorie sweeteners cause cravings that lead you to eat more.
Adults who switched from sugary to diet drinks lost more weight (though still a modest amount) than those who didn’t switch. And in growing children, diet drinks led to less gain in body fat than sugary drinks. One study suggested that different low-calorie sweeteners may have different impacts on weight, but only saccharin (no longer frequently used) led to weight gain in adults.
More research is needed to know if and how low-calorie sweeteners alter the gut microbiome...and how those changes might affect our health. For now, one small study suggests that only sucralose and saccharin change the gut microbiome and raise blood sugar in sensitive people.
Food companies use low-calorie sweeteners to make junk food look healthy. If you’re simply switching from sugar-laden cookies, ice cream, and brownies to those made with low-calorie sweeteners, you’re missing the big picture.
Want a sweet treat? You’re better off with foods made with whole fruit, whole grains, or low-fat dairy (or its plant-based counterparts). A cupcake made with stevia is still a cupcake.
This article comes from Nutrition Action. We don't accept any paid advertising or corporate or government donations. Any products we recommend have been vetted by our staff and are not advertisements by the manufacturers.
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