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Aspartame: It’s sweet to eat, but is it a trick or a treat?

While you shouldn’t eat it by the bowl, it hardly affects glycemic control

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Study under review: Aspartame Consumption for 12 Weeks Does Not Affect Glycemia, Appetite, or Body Weight of Healthy, Lean Adults in a Randomized Controlled Trial

Introduction

Obesity is a growing problem, not only in the U.S., but increasingly around the world. Recent epidemiological and clinical evidence suggests that sugar consumption can lead to excess calorie intake and therefore promote the development of obesity[1] and metabolic disorders[2] like diabetes. Artificial sweeteners like aspartame have been studied as a potential sugar substitute in foods and beverages.

Aspartame is often referred to as a nonnutritive sweetener, but not because aspartame is lacking in calories. Aspartame is a synthetic conjugation of two amino acids: aspartic acid and phenylalanine (which is also why it is called an “artificial” sweetener). It has an energy value of about four kcals per gram[3], like protein or sugar. However, as you can see in Figure 1, because aspartame is 200 times[4] more potent than table sugar at triggering the sensation of sweetness, far less is needed when manufacturing sweet-tasting foods or beverages. This means that if you were regularly consuming sugar-sweetened soft drinks that contained 150 kcals each, you could switch to a diet soft drink containing a nonnutritive sweetener like aspartame and ingest less than one kcal. This relatively simple substitution could have implications for people with diabetes and dramatic impacts on the development of obesity.

However, the research on aspartame is not crystal clear. For example, a paper published in 1988[5] raised the possibility that aspartame could negatively affect the satiety response and lead to overconsumption. Yet, in 1994, the results of two human trials[6][7] concluded there was no difference in energy intake for individuals that “preloaded” meals with aspartame and those that did not. This seemed to put an end to the confusion until 1997, when a study claimed[8] that women consuming aspartame-sweetened beverages over-ate the day after consuming the drink compared to women drinking sugary beverages or mineral water.

The back-and-forth continued with a 2006 meta-analysis indicating consumption of aspartame is associated with a significant decrease in energy consumption and weight relative to sugar consumption. In 2010, a new hypothesis[9] was offered that suggested artificial sweeteners do indeed promote feeding behavior if the artificially-sweetened food or beverage does not satisfy our food reward pathways.

To muddy the waters further, evidence concerning whether aspartame or other artificial sweeteners stimulate an insulin response or affect glucose tolerance is seemingly conflicted. A 2016 review of the literature[10] discussed rodent studies that indicated aspartame led to impaired glucose tolerance, while a 2017 review[11] pointed out that human trials to date had observed no effect.

It is unclear how exactly aspartame would have these effects on glucose and insulin, as the proposed mechanisms have not been extensively studied. A popular hypothesis is that aspartame and other sweeteners stimulate[12] a cephalic phase insulin response. That is, the sweet sensation you get from tasting something sweet can stimulate the release of insulin before your food is absorbed. Another hypothesis is that since aspartame is a flexible molecule[13] that can bind to sweet taste receptors, it may also be possible to stimulate signal transduction elsewhere in the body that might alter glucose uptake or insulin release. More recently, scientists have proposed that any changes in insulin sensitivity may be mediated by aspartame's effect on the gut microbiome[14].

Human studies are needed to further investigate the role artificial sweeteners like aspartame play in our metabolism and feeding patterns. The study under review sought to clarify some of the discord on the subject by examining different levels of aspartame consumption and how it affects glycemia, appetite, and body composition.

Aspartame is an artificial sweetener made from two amino acids that is widely used in foods and beverages to replace sugar while reducing calorie content. However, there is some controversy over how effective aspartame is at controlling glucose, and the present study sought to clarify this.

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Other Articles in Issue #45 (July 2018)