What is aspartame?
Aspartame is one of the most common artificial sweeteners in use today. It is sold under the brand names NutraSweet® and Equal®. Aspartame is composed mainly of 2 amino acids, aspartic acid and phenylalanine. Amino acids are the building blocks of proteins and are found naturally in many foods. Aspartame is used in many foods and beverages because it is about 200 times sweeter than sugar, so much less of it can be used to give the same level of sweetness. This, in turn, lowers the calories in the food or beverage. Rumors claiming that aspartame causes a number of health problems, including cancer, have been around for many years. Many of these continue to circulate on the Internet. How are people exposed to aspartame?
Aspartame has been used in the United States since the early 1980s. It is now found in thousands of different food products. Aspartame is commonly used as a tabletop sweetener, as a sweetener in prepared foods and beverages, and in recipes that do not require too much heating (since heat breaks down aspartame). How is aspartame regulated?
In the United States, artificial sweeteners such as aspartame are regulated by the Food and Drug Administration (FDA). These products must be tested for safety and approved by the FDA before they can be used. The FDA also sets an acceptable daily intake (ADI) for each sweetener, which is the maximum amount considered safe to consume each day during a person's lifetime. The ADI is set to be about 100 times less than the smallest amount that might cause health concerns, based on studies done in lab animals. The FDA has set the ADI for aspartame at 50 milligrams per kilogram (mg/kg) of body weight. (In the European Union, the European Food Safety Authority has recommended a slightly lower ADI for aspartame, at 40 mg/kg.) To put the ADI for aspartame in perspective, this would be 3,750 milligrams per day for a typical adult weighing 75 kilograms (about 165 pounds), far more than most adults take in daily. A can of diet soda usually contains about 180 milligrams of aspartame, so a typical adult would have to drink about 21 cans of diet soda a day to go over the recommended level. Does aspartame cause cancer?
Researchers use 2 main types of studies to try to determine if a substance or exposure causes cancer. (A substance that causes cancer or helps cancer grow is called a carcinogen.) In studies done in the lab, animals are exposed to a substance (often in very large doses) to see if it causes tumors or other health problems. It's not always clear if the results from these types of studies will apply to humans, but lab studies are the best way to find out if a substance has the potential to cause cancer in humans before widespread exposure occurs. Another type of study looks at cancer rates in different groups of people. Such a study might compare the cancer rate in a group exposed to a substance versus the rate in a group not exposed to it, or compare it to what the expected cancer rate would be in the general population. But studies in people can sometimes be hard to interpret, because there may be other factors affecting the results that are hard to account for. In most cases neither type of study provides definitive evidence on its own, so researchers usually look at both lab-based and human studies if they are available. Studies done in the lab
Many studies have looked for health effects in lab animals fed aspartame, often in doses higher than 4,000 mg/kg per day over their lifetimes. These studies have not found any health problems that are consistently linked with aspartame. Two studies published by a group of Italian researchers suggested that very high doses of aspartame might increase the risk of some blood-related cancers (leukemias and lymphomas) in rats. However, both the FDA and the EFSA have called these results into question, citing a lack of some important data in the published studies and other concerns. Studies in...