by Dr. Erin Glynn, Unicity Scientific Advisory Board member
We all know eating a diet high in added sugars is bad for health. That’s why reduced- or no-calorie sweeteners (also called non-nutritive sweeteners) are often used in foods, beverages, and dietary supplements to reduce the amount of sugar used. Most commonly recognized for their use in sodas, these non-nutritive sweeteners can be found in everything from salad dressings and ketchup to packaged breads and cereals. In this article, we take a closer look at non-nutritive sweeteners and explore some of the common questions and misconceptions over these sugar alternatives.
What are the main non-nutritive sweeteners?
Non-nutritive sweeteners fall into two major classes: natural and artificial. The most commonly used natural non-nutritive sweeteners include stevia (from Stevia rebaudiana leaves), monk fruit (from Luo Han Guo fruits), and sugar alcohols such as erythritol, xylitol, and sorbitol. The most popular artificial non-nutritive sweeteners include aspartame—commonly used in diet sodas—and sucralose, also known as Splenda.
Gram for gram, stevia is about 200-400 times sweeter than sugar, depending on which steviol glycosides are included in an extract. Steviol glycosides are the compounds in stevia leaves that make it sweet, and commercial stevia sweeteners include highly purified extracts of these glycosides. Stevia contains no calories and is generally well tolerated.
Mogrosides are the sweet compounds in monk fruit that make it about 100-250 times sweeter than sugar. Similar to stevia extracts, monk fruit extracts do not contribute any calories and are well tolerated.
As for sugar alcohols, xylitol is about as sweet as sugar while erythritol and sorbitol are less sweet (~20-40% less). Sugar alcohols occur naturally in various fruits, vegetables, and plants, but unlike stevia and monk fruit, this class of sweeteners does contribute some calories and can have side effects. Xylitol and sorbitol have 2.4 and 2.6 calories per gram, respectively, and can both cause digestive issues like gas, bloating, and diarrhea—especially at higher amounts. On the other hand, erythritol is unique in that it only has 0.24 calories per gram and is typically well tolerated, even at higher amounts.
While there are other low- or no-calorie artificial sweeteners, here we will focus on the two most widely used: aspartame and sucralose. Aspartame is about 200 times sweeter than sugar, and while it does contain about 4 calories per gram, it does not contribute a meaningful amount of calories since such a low quantity is used. Aspartame can cause digestive symptoms in some individuals, and some report it may trigger migraine headaches, though studies show mixed results.
Sucralose is about 600 times sweeter than sugar. It is made by a chemical reaction with a natural sugar molecule, resulting in a new molecule that is sweeter than sugar but that our bodies do not recognize or treat like a carbohydrate. Because we cannot metabolize it, sucralose has no calories. Potential side effects include digestive upset, typically when consumed in higher amounts.
Regulatory approvals and safe amounts
These non-nutritive sweeteners are generally recognized as safe by global regulatory authorities like the U.S. Federal Drug Administration (FDA), Health Canada, and the European Food Safety Authority when consumed within the Acceptable Daily Intake (ADI) recommendations. For example, the ADI for aspartame is 50 milligrams per kilogram of body weight per day (or about 22.7 mg per pound of body weight per day). This means a person weighing 150 pounds could consume up to 3.4 grams of aspartame per day safely. For comparison, a typical diet soda sweetened with aspartame contains 50-200 mg, well below the ADI limits. It would be very hard to reach over 3 grams of aspartame per day, even if consuming multiple servings of products containing aspartame.
The ADI for sucralose is 5 milligrams per kilogram body weight per day (~2.27 mg per pound body weight per day). For our 150-pound person, this would mean consuming up to about 300 mg of sucralose per day is safe. A typical beverage sweetened with sucralose could contain as little as a few milligrams up to about 100 mg for a very sweet beverage.
The ADI for Rebaudioside A, the most commonly used steviol glycoside, is 12 mg/kg body weight per day (~5.4 mg per pound body weight). For a 150-pound person, up to about 720 mg stevia (as Reb A) per day is considered safe. A typical beverage sweetened with stevia could contain as little as a few milligrams to about 50 mg per serving.
ADIs have not been established for sugar alcohols or monk fruit, due to their high safety profile and low risk of adverse effects.
Despite global regulatory acceptance and safety agreement within standard usage ranges, some still question the health effects of non-nutritive sweeteners, particularly artificial sweeteners. Most of the concerns raised stem from animal studies in which a given sweetener (mainly aspartame or saccharin) caused adverse effects in the animals such as cancer or neurological effects. However, these studies consistently used much higher amounts of the sweeteners than what would be typical (or even high) human consumption. In addition, the global body of scientific evidence in humans shows no or weak association between artificially sweetened beverage consumption and cancer incidence, cancer death, cardiovascular death, kidney disease, and others.
More recently, questions have been raised regarding the effects of non-nutritive sweeteners on metabolic health. Several recent studies have investigated the effects of various non-nutritive sweeteners on the gut microbiome, glucose tolerance, insulin sensitivity, obesity, and more. Findings have been mixed, but tend to favor the natural alternatives like stevia over artificial options.
High intake of artificially sweetened beverages has been associated with obesity and type 2 diabetes in some meta-analyses of existing data, but strong causal links have not been identified. More recent human studies point to potential changes in the gut microbiota following non-nutritive sweetener consumption as a potential mechanism regulating changes in metabolic outcomes. However, as with most studies of the human gut microbiome, individual results vary greatly and make it challenging to extrapolate results to larger populations. In addition, the few existing well-designed clinical trials investigating the effects of these sweeteners on metabolic health outcomes vary widely in the population studied, dosage used, protocol followed, and outcomes measured.
In short, more information is needed before any population-based recommendations to further limit non-nutritive sweeteners should be made, and study results regarding one sweetener should not be generalized to others.
The take-home message
Current scientific evidence suggests that when used in moderation, non-nutritive sweeteners are considered safe within the established ADI limits. New research indicates certain sweeteners may alter the gut microbiome and influence carbohydrate metabolism, but results are currently mixed and inconclusive as to the exact population(s) that may be affected and the true long-term impact of these changes.
To support overall health, look for ways to reduce added sugar intake naturally, such as consuming whole foods like fruit when you have a sweet tooth. Aim to reduce the sweetness of your diet overall by consuming more unsweetened foods and beverages, which can help reduce sweet cravings and preference for sweets over time. Consuming non-nutritive sweeteners in moderation can help keep your added sugars low and be part of a healthy lifestyle.
Dr. Erin Glynn is an expert in human physiology, nutrition, and metabolism. She earned her bachelor’s degree in exercise physiology from Texas A&M University and her doctorate in biomedical science, specializing in preventive medicine, from the University of Texas Medical Branch. Dr. Glynn completed a postdoctoral fellowship at the Duke University Medical Center, where she focused on the metabolic profiling of metabolic diseases, including obesity and diabetes. Since 2015, Dr. Glynn has focused her work on research and development of dietary supplements and targeted programs for metabolic health. She is an active member of the American Society for Nutrition and founder of Nuchi Health, a company focused on consumer health and education.