It’s a dieter’s and diabetic’s dream come true, artificially sweetened products they can consume all day without worrying about sugar. Sounds almost too good to be true. As a clinical nutritionist I was skeptical and decided to examine this phenomena closer. First of all, when you ask most consumers of diet soda to tell you what type of sweetener is added they will simply respond “aspartame.” But if you probe further and ask what’s in aspartame, they will likely shrug they shoulders and once again repeat “aspartame.” Most people are not aware of aspartame’s composition because there are no requirements to list its individual ingredients on food labels.
Aspartame was originally discovered by accident in 1965 by a chemist working for the Searle Company. He was actually testing an ulcer drug when he spilled some chemicals on his hand. Later when he licked his finger to turn a page, he experienced an intensely sweet taste. He was amazed to discover how sweet this substance was when he accidentally tasted it. Searle submitted their own safety studies and obtained FDA approval to market aspartame. They formed the NutraSweet Company, which is now owned by Monsanto. Today, aspartame is widely available and can be found in almost 9,000 food products.
Aspartame’s popularity with dieters comes from the fact that it can sweeten a wide variety of foods without adding any additional calories. Unfortunately, this may not be without a price. Aspartame tastes about 200 to 400 times sweeter than sugar. This creates a problem, because the brain is fooled into believing an abnormally high amount of glucose has entered the bloodstream. In response, the pancreas is stimulated to secrete insulin to lower serum glucose levels. This may cause blood sugar levels to fall below normal leading to a serious condition known as hypoglycemia. The brain’s preferred source of energy is derived from glucose and when blood sugar levels fall too low, the brain panics and sends out food craving messages. This may cause the individual to actually eat more food (usually the wrong foods such as high sugar/high fat). This will sabotage any weight loss intentions.
Aspartame’s three ingredients can be found in any nutrition or biochemistry textbook. It’s 40% aspartic acid, (an amino acid) and 50% phenylalanine, (another amino acid). Both of these amino acids are bound to a molecule of methanol (wood alcohol), which comprises the remaining 10% of this all- natural, artificial sweetener. Since it contains two amino acids, it is not considered a carbohydrate.
Let’s explore the ingredients separately, starting with aspartic acid. This amino acid in free form (unbound) can pass the blood brain barrier and accumulate in the brain. Once there, it has the potential to act as an “excitotoxin” and it can excite or over stimulate neurons.
Excess levels of phenylalanine in the blood can interfere with the brain’s absorption of another amino acid, tryptophan. This in turn can result in lower levels of the neurotransmitter serotonin since tryptophan is required for its production. Decreased serotonin levels in the brain may be associated with depression. In addition, since serotonin is a precursor to the hormone melatonin, sleep disorders may also be a consequence.
One serious caution for the use of aspartame may involve individuals with the genetic disorder known as phenylketonuria (PKU). In this instance, the enzyme required to metabolize phenylalanine is defective and compounds known as phenylketones are produced. This substance accumulates in the blood and may cause brain damage in these individuals.
Once aspartame enters the small intestine, methanol is released and absorbed into the body. Methanol is then metabolized to formaldehyde (embalming fluid) and to formic acid (normally found in the sting of red ants). Due to its low excretion rate, the EPA considers methanol a cumulative poison. They recommend that the consumption of methanol be limited to 7.8 mg per day. It is interesting to note that one 8 ounce serving of a diet beverage contains 14 mg of methanol. Symptoms of methanol toxicity includes vision problems, headaches, dizziness, nausea, gastrointestinal disorders, weakness, behavioral changes and memory loss.
Aspartame has been widely tested on rodents, with no reported deaths attributed to aspartame consumption. However, one possible confounding variable in these safety studies is the fact that rodents have different enzyme systems than humans and are better able to metabolize aspartame. Therefore, it can be concluded that it is perfectly safe to give aspartame to your pet rat.