What To Know About Aspartame

Medically Reviewed by Christine Mikstas, RD, LD on July 10, 2023
3 min read

While there is no debate about the effectiveness of aspartame in sweetening your food, there is a great deal of confusion about its safety and its effectiveness as an aid to weight loss or blood sugar regulation for people with diabetes. Still, this low-calorie sweetener is widely used in the manufacture of foods and beverages sold with the labeling “diet,” “low sugar,” or “low calorie.” 

Today, aspartame is the most commonly used and consumed low-calorie sweetener in the United States. But, what is aspartame exactly, and what is fueling the ongoing debate about its safety and effectiveness? 

Aspartame is a low-calorie sweetener — a substance that tastes sweet but doesn't contain natural sugars or any calories if used in small amounts. Developed in 1965, aspartame has been widely tested by both government-funded and independent laboratories. Right now, you can find it in thousands of food items around the world, even though its safety is still being questioned. 

Chemically, aspartame is quite simple — made of two naturally occurring amino acids: aspartic acid and phenylalanine. It looks like a fine white powder and is almost 200 times sweeter than sucrose — otherwise known as sugar.  While it is not actually completely free of calories, the amounts of aspartame needed to sweeten foods and drinks to the same level as table sugar are very small and do not add to the calorie count. 

Aspartame’s use as an aid for weight loss is highly debated. The common-sense belief and early marketing held that a product sweetened like sugar but did not have as many calories as sugar would lead you to lose weight.

Switching to foods and drinks containing aspartame instead of sugar led to successful weight loss in some people, but several others did not lose any weight, with some of them even gaining weight when using aspartame to sweeten their food and drink. 

Some studies have found that consuming aspartame can slow down your metabolism, thus leading to weight gain even if fewer calories were consumed. Other studies found this not to be the case. The confusion continued until a study, done by Yale in 2020, found an answer. 

The study found that consuming a low-calorie sweetener was not, by itself responsible for slowing metabolism. However, when combined with other carbohydrates, or fats, the consumption of the non-sucrose sweetener did lead to a significant drop in metabolic rate.

Similar to the debate over aspartame's effectiveness as a tool for weight loss, the debate over its safety for those with type 2 diabetes also continues. Consuming aspartame seems to have little or no effect on your blood glucose levels — seemingly indicating that it is a safe alternative for people with diabetes craving something sweet.  

Additional studies have found that when you eat or drink products containing aspartame it increases cortisol levels and alters the activity of the microbes responsible for the breakdown of food in your digestive tract. It is thought that these changes may lead to weight gain and insulin resistance — both of which would have a negative effect on blood sugar control in those with type 2 diabetes.

Apart from the debates over its effectiveness in helping you to lose weight or regulate your blood sugar levels if you have type II diabetes, there is an ongoing concern about aspartame's negative effect on your health. However, the debate over the safety of aspartame seems to be mostly between science and public opinion. 

While it is true that some evidence was found in early studies of a link between the consumption of aspartame and cancer in rats, later studies could not find a link between aspartame consumption and cancer in nonhuman primates or human beings.

Also, aspartame has been used widely all over the world for over thirty years now, and no link has been found between its consumption and cancer or any other disease or illness. Still, the court of public opinion is unsure about the safety of this product. This despite the fact that the US FDA and the European Food Safety Authority — after decades of studies and anecdotal evidence — have deemed aspartame to safe for your consumption, even in large quantities.