We’re back with another installation of Sound Science, our article series that spotlights high-quality evidence from scientific studies that may have flown under your radar.
We are born with a preference for sweet taste. Although the desire fades for some as we age, to some degree we all have a sweet tooth. Sweetness often comes with calories. To deliver sweet taste without calories, low-calorie sweeteners (LCS) were developed, and in some cases like aspartame, they were discovered by chance. But the body of evidence on LCS published in peer-reviewed literature did not accumulate by chance. Decades of high-quality scientific research have provided answers to many questions about LCS. In this article we take a look at two important areas of research on LCS – safety and body weight, and where the scientific literature currently stands.
The first question that comes to many people’s minds about LCS is ‘are they safe’? The short answer is yes; LCS are some of the most studied ingredients in the history of our food supply. For a food ingredient or food additive to be used in the U.S., it must first be evaluated for safety by the U.S. Food and Drug Administration (FDA). The FDA currently permits the use of eight types of LCS: six are FDA-approved – acesulfame potassium, advantame, aspartame, neotame, saccharin, sucralose, and two – monk fruit extract and stevia leaf extract, have a status known as Generally Recognized As Safe (GRAS).
In addition to health authorities in the U.S., regulatory agencies in Australia and New Zealand, Canada, China, Europe and Japan also independently monitor and confirm safety evaluations of LCS. Most recently in 2017, the European Food Safety Authority (EFSA) reviewed and confirmed the safety of sucralose. In 2013, EFSA also re-evaluated and confirmed the safety of aspartame. While not a regulatory agency, the 2015 U.S. Dietary Guidelines Advisory Committee (DGAC) reviewed aspartame’s impact on human health and agreed with the EFSA conclusion that aspartame is safe for consumption at current intake levels.
But exactly how much LCS is considered safe to consume? The LCS permitted by the FDA have undergone extensive research to confirm its safety, and Acceptable Daily Intakes (ADI) have been established for each LCS, with the exception of monk fruit sweeteners. According to the FDA, there are several reasons why an ADI might not be established, including evidence of safety at consumption levels that are well above the amount needed to sweeten a food or beverage.
The ADI represents the average amount determined through extensive research, that is expected to be safe for a person to consume each day during their lifetime. The ADI is established to be 100 times lower than the highest intake amounts shown to have no adverse effects in lifetime animal studies; this helps ensure that human intake will be safe.
The ADI can be a hard concept to grasp, so here’s a tangible example: the ADI for aspartame is 50 milligrams per kilogram (mg/kg) of body weight per day. If you weigh 150 pounds or 68 kg, then your ADI per day for aspartame is about 3,400 mg – or equivalent to the amount in about 19 cans of diet soda or more than 85 individual tabletop sweetener packets. The ADI should not be confused with a daily intake recommendation; it is not one. It is simply a level of average daily intake over a lifetime, established by rigorous toxicological safety assessments that have been shown to have no adverse effects.
With increased attention in recent decades to addressing the prevalence of obesity, more products are turning to LCS as a way to reduce calories while retaining sweetness. A 2017 observational study found that the percentage of Americans who report consuming products that contain LCS is on the rise since 2000. However, estimates of LCS consumption have shown that intake is far below established ADIs, both globally and in the U.S.
LCS are designed to impart sweetness while reducing the number of calories from added sugars, which can help support weight management. Losing or maintaining body weight is often cited in IFIC’s annual Food & Health Survey as a top perceived benefit of consuming LCS. Researchers continue to study the efficacy of LCS in weight loss and weight maintenance. Some researchers are also studying hypotheses regarding the potential roles of LCS in weight gain.
The predominant view among nutrition scientists is that weight loss is best achieved by creating a calorie deficit—consuming fewer calories than we use. This can be a tricky proposition as many factors influence behavior, food decisions, physical activity and the way our bodies respond to what we eat and drink.
LCS can be helpful in lowering the calories we take in. Results from randomized controlled trials support that reducing total calorie consumption by displacing calories from added sugars using LCS can lead to modest weight loss. Based on their systematic review of observational and intervention studies, the Scientific Report of the 2020 DGAC concluded that LCS should be considered an option for managing body weight. However, that doesn’t mean that losing weight is as simple as choosing to consume LCS or products that contain them. Reviews of research with various study designs illustrate that calorie deficits and surpluses matter. In other words, adding or subtracting foods, beverages, nutrients or ingredients from the diet, without altering the total number of calories consumed or level of physical activity, makes a change in body weight less likely to occur.
While most of the attention given to LCS tends to focus on weight loss, theories about how LCS may promote weight gain have been suggested, although physiological mechanisms for such hypotheses have not been proven. Opinions about whether or not LCS contribute to weight gain can largely be explained by the type of evidence used to support a particular point of view. For example, a 2018 review of the relevant scientific literature concluded that evidence from observational studies show an association between LCS intake and higher body weight; however, evidence from randomized controlled trials demonstrate that LCS may support weight loss. A 2021 citation analysis came to a similar conclusion; literature reviews that show a relationship between LCS intake and lower body weight mostly rely on data from randomized controlled trials while reviews citing mostly observational studies show a relationship between LCS and higher body weight.
One potential confounding factor in observational research findings is that people who weigh more may seek LCS-containing products more often, particularly in beverages, to lower total calorie intake in the effort to lose weight. This is often referred to as reverse causality. In other words, while observational studies can be important for generating hypotheses, they cannot determine whether LCS are making people heavier or if people who weigh more are disproportionately consuming LCS. In contrast, the intervention trials that are designed to test cause and effect have consistently failed to demonstrate that LCS cause weight gain.
The Low-down on LCS
LCS are some of the most extensively studied ingredients in our food supply, and research continues to examine the connection between LCS and human health. Decades of scientific inquiry by global health authorities have repeatedly established and confirmed the safety of LCS, and evidence from randomized controlled trials show that LCS can be beneficial in weight management.
Research is also crystal clear that LCS do not have magical abilities to burn fat or calories, increase energy levels or make us healthier. LCS themselves are benign — not good or bad; thus, they do not make products healthy or unhealthy.
The low-down on LCS is this; consuming LCS is not required for good health, but they are a safe option for people who are looking to reduce calories, carbohydrates and added sugars without sacrificing a sweet taste.
Looking for more information? Check out our “Everything You Need to Know” articles on aspartame, monk fruit sweeteners, stevia sweeteners and sucralose for coverage of topics beyond body weight and safety, including LCS intake by children, people with diabetes and during pregnancy, as well as potential effects on appetite and the microbiome.
If you are a Commission on Dietetic Registration (CDR) credentialed practitioner, you can receive continuing professional education (CPE) for completion of IFIC recorded webinars and self-study activities, which can be accessed here.
This article includes contributions by Allison Webster, PhD, RD.