The Truth About Artificial Sweetners: Aspartame

Artificial sweeteners are present in many foods consumed by Americans. Their use is beneficial in that they provide sweetness, increasing the palatability of foods without the added sugar and resulting calories, an important adjunct to weight loss and diet regimens. Most artificial sweeteners are not metabolized by the body and are therefore considered safe. However, scientists disagree about safety because the metabolites of the “non-metabolized” compounds have been shown to produce deleterious effects in mice, rats, and dogs.

Read Part 1 Saccharin

In 1965, a chemist at G. D. Searle was studying new treatments for gastric ulcers. Accidentally, a small amount of the compound landed on the chemist’s hand. Without noticing the compound, the chemist licked his finger and discovered a sweet taste. After realizing it was from the powder intermediate and believing it was not likely to be toxic, he again tasted the intermediate and found it was indeed sweet aspartame.

Aspartame was first approved by the FDA in 1981 as a tabletop sweetener; in 1996, it was approved as a general-purpose sweetener in all foods and drinks. Since its approval, aspartame has been used in more than 6,000 products by hundreds of millions of people in countries all around the world. It is 200 times sweeter than sucrose and is marketed under the brand names Equal and NutraSweet. Aspartame can be found in a wide variety of prepared foods (e.g., carbonated and powdered soft drinks, chewing gum, confections, gelatins, dessert mixes, puddings and fillings, frozen desserts, and yogurt), tabletop sweetener, and some medications (e.g., vitamins and sugar-free cough drops).

Because it contains phenylalanine, the FDA has mandated packaging bear a warning label to prevent individuals with the rare genetic disorder phenylketonuria from ingesting this substance. The Institute of Medicine’s Food and Nutrition Board has not issued upper tolerable intake levels for either aspartate or phenylalanine based on available data and models of chronic exposure (Institute of Medicine, 2005). Phenylalanine is an amino acid used as a building block for proteins. Individuals who suffer from phenylketonuria lack or have insufficient amounts of the enzyme phenylalanine hydroxylase, required to breakdown phenylalanine. Without the presence of this enzyme, phenylalanine accumulates. Phenylalanine buildup can significantly alter human brain function. All children are screened for this rare disorder in the United States.

Click for a close up look at the WARNING label on pure Aspertame

Upon ingestion, aspartame is broken down into its components, aspartic acid, phenylalanine, and methanol. These components are then absorbed into the blood and each is metabolized. It has been hypothesized that neither aspartame nor its components accumulates in the body. These components are used in the body in the same ways as when they are derived from common foods. Following a single aspartame dose of 34 mg/kg, 12 normal adults demonstrated no increase in plasma or red blood cell aspartate concentrations; however, phenylalanine concentrations doubled within an hour and returned to baseline in 4 hours. One of its metabolites, methanol, has been shown to further metabolize into formaldehyde and formic acid.

By far, aspartame has been the most controversial artificial sweetener because of its potential toxicity. Numerous websites are devoted to removing aspartame from all sources immediately. New research provides evidence of the carcinogenic potential of this compound. Research using rats, has demonstrated a significant increase of malignant tumors in males, an increase in the incidence of lymphomas and leukemias in males and females, and an increase in the incidence of mammary cancer in females. These results reinforce and confirm previous research that also demonstrated the carcinogenicity potential of aspartame and the increased carcinogenetic potential if exposure occurs during gestation. It is notable that the dosage tested approximated the acceptable daily intake for humans.

In other published reports, women ages 40, 32, and 26 all experienced migraines while chewing a popular gum with aspartame additive. In all cases, the migraines were relieved after cessation of product use. The headaches were reproducible by reintroducing the gum. Phenylalanine doses in the first few years of life produced irreversible brain damage in monkeys. Another report was of a 10-year-old girl who developed a decline in platelet count, coupled with enlargement of the liver and spleen, and a marked increase in histiocytes in the bone marrow. A dramatic  normalization followed when additives were eliminated from her diet.

Diet beverages may represent the optimal use of intense sweeteners in weight control because they have the advantage of reducing the energy density of the product to zero. Studies indicate some modest weight loss has been shown when artificial sweeteners are used, but they go on to note that they are not appetite suppressants. However, additional research indicates it is not only the amount of calories contained in these substances that can have an effect on obesity and metabolism.

For example, the cycle of sweetness and obesity may be difficult to break. Researchers have equated the addictiveness of sweets to that of cocaine in rats. Their findings demonstrated increased intake of no-calorie sugar substitutes could promote increased food intake and body weight gain.