We’re back with another installation of Sound Science, the forum where we spotlight quality research studies and scientific conclusions that may have flown under your radar. This time, we’re looking at low-calorie sweeteners (LCSs).We like sweet foods—there’s just no denying it. In part, it’s because we’re born with a preference for sweet taste. Although the desire fades for many as we age, to some degree we all have a sweet tooth. In an effort to deliver sweet taste without calories, LCSs have been developed and, in some cases, discovered by chance. But the body of evidence on LCSs in the peer-reviewed literature didn’t happen by chance. Decades of high-quality scientific research has provided answers to many of the questions we have about LCSs. But there is still more that we hope to learn about in the coming years and new areas of LCSs research that we’re just starting to explore. Let’s take a look at the Sound Science supporting LCSs.
The first question that comes to many people’s minds about LCSs is if they’re safe for themselves and their family to consume. For an ingredient or additive to be allowed in food, safety is the primary question that the U.S. Food and Drug Administration (FDA) sets out to answer. Today, the FDA permits the use of eight types of low and no-calorie sweeteners. Six are FDA-approved (acesulfame potassium, advantame, aspartame, neotame, saccharin and sucralose) and two (monk fruit extract and stevia leaf extract) have a status known as GRAS, or Generally Recognized As Safe. The logical follow-up question is: How much is safe to consume? LCSs permitted by FDA have undergone extensive safety testing and, as a result, each LCS has what’s known as an Acceptable Daily Intake (ADI). The ADI represents 1/100th of the average amount a person could safely consume each day over a lifetime. The FDA often uses a built-in safety factor of 100 when establishing ADI. Because this can be hard to conceptualize, here’s a tangible example: The ADI for aspartame is 50 milligrams per kilogram (mg/kg) of body weight. If you weigh 150 pounds (68 kg), then your ADI for aspartame is about 3,400 mg, or equivalent to the amount in about 19 cans of diet soda. This amount is not a recommendation; it is simply a level established by rigorous toxicological safety assessments. A recent study showed that the percentage of Americans who self-report consuming LCS-containing products is on the rise, though U.S. and global intakes have been shown to be far below established ADIs. Safety evaluations of LCSs by health authorities occur around the globe. 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 reviewed aspartame’s impact on human health and agreed with EFSA’s conclusion that aspartame is safe for consumption as current intake levels.
Because LCSs are designed to remove calories from foods and beverages, the impact on body weight is often central to LCS usage and perceived benefits. Researchers continue to study the efficacy of LCSs in weight loss and weight maintenance. Some researchers are also testing hypotheses regarding potential roles of LCSs in weight gain. Generally speaking, weight loss results from creating a calorie deficit—expending more calories than we take in. In the attempt to create a calorie deficit, there are three options: Eat fewer calories, be more physically active or do both simultaneously. LCSs can be helpful in lowering the calorie side of the equation, and results from randomized control trials show that reducing total calories, specifically by using LCSs in place of calories from sugar, does lead to modest weight loss. But that doesn’t mean that losing weight is as simple as making the choice to consume LCSs.
Reviews of research containing various study designs indicate that overall calories in vs. calories out matters most. In other words, adding or subtracting components to the diet, LCSs included, without a change in total calorie intake or physical activity will not lead to a change in body weight. While the general public’s attention tends to focus on weight loss with respect to LCSs, factors involved in weight maintenance are important for researchers to better understand obesity trends. People who have achieved significant weight loss often find it difficult to maintain. There are a variety of reasons for this, some biological and some behavioral.
The National Weight Control Registry has documented successful approaches for sustained weight loss, and using LCSs has been reported as a top strategy. The idea that LCSs may promote weight gain has been speculated, though the physiological mechanisms for the hypothesis have not been proven. The issue of whether LCSs “cause” weight gain can be explained by looking at the types of evidence used to support a particular point of view. A recent review showed that observational studies were more likely to associate LCS intake with higher body weight, whereas randomized control trials may support weight loss. Part of this discord in the scientific literature is explained by potential confounding factors in observational research. For example, people may compensate for their LCS calorie “savings” by choosing more calorie-dense foods later on. If a person frequently compensates by taking in more calories than they “saved,” weight gain could result. Current evidence shows that while compensation for calorie-saving choices exists, the number of calories saved from LCSs tend to outweigh the amount of calories consumed as a result of compensating. Another potential confounding factor in observational research findings is that overweight or obese people may seek LCS-containing items, particularly 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 research can be critical for generating hypotheses, it can’t tease out if LCSs are making people overweight or if overweight people are disproportionately consuming LCSs. In contrast, the intervention trials that are designed to test cause and effect have repeatedly failed to illustrate that LCSs cause weight gain.
The low-down on LCSs
LCSs are some of the most extensively studied ingredients in our food supply, and research continues on the connection between LCSs and human health. Decades of scientific inquiry have repeatedly established the safety of LCSs and that, depending on how they’re incorporated into the diet, LCSs can be helpful in weight loss and weight maintenance. Research is also crystal clear that there is nothing magical about the ability of LCSs to burn fat, calories, increase energy levels or to make us healthy. LCSs themselves are benign — not “good” and not “bad” — thus, they don’t make products “healthy” or “unhealthy.” And yet, too often, this fact is misinterpreted with false balance—the idea that a single outlying study showing negative health outcomes outweighs an entire body of literature that supports LCS usage. The low-down on LCSs is that they don’t have to be “liked” or used by everybody, but they are a safe option for people who are looking for ways to reduce calories, carbohydrates and sugars in the diet without sacrificing sweet taste. Whether the goal is weight loss, weight maintenance or even not related to weight, LCSs do what they are intended to do: offer people the ability to enjoy foods and beverages with fewer calories.
This blog includes contributions by Allison Webster, PhD, RD.
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