For years, conspiracy theorists and urban mythology websites have warned about the dangers of aspartame, going so far as to implicate the U.S. Food and Drug Administration in a plot against North Americans, since the FDA has failed to respond to their concerns by banning the sugar replacement. One of the components activists point to as being dangerous is the amino acid Phenylalanine, abbreviated as Phe.
“Phenylalanine is a neurotoxin and excites the neurons in the brain to the point of cellular death”, says Janet Starr Hull, creator of the so-called 'aspartame detox program' and owner of the website
Sweetpoison. “ADD/ADHD, emotional and behavioral disorders can all be triggered by too much Phenylalanine in the daily diet.”
Today, Phe is emerging in a role separate from its traditional role as a component of aspartame and is being included with dietary supplements for its reputed mood elevation properties, so it’s worthwhile taking a look at the real story behind Phe and its safety.
Phenylalanine (HO2CCH(NH2)CH2C6H5) is an essential amino acid, meaning you need it in your diet. However, humans can’t synthesize it themselves, and must therefore obtain it from dietary sources or supplements. Fortunately, it’s found in virtually all proteins, in foods such as eggs, milk, cheese, nuts, bananas, poultry, fish and whole grains, in three forms: D-phenylalanine (DPA), L-phenylalaline and D-L phenylalaline. While dietary deficiency is rare, it can occur in low-protein diets, where it would be characterized by lethargy, edema, weakness, or skin lesions, as well as liver damage and slow growth.
Phenylalanine uses the same active transport channel as tryptophan to cross the blood-brain barrier. The DPA form, which doesn’t have a role in protein biosynthesis, is nevertheless present in small amounts in proteins, particularly aged proteins and in processed foods. While the biological functions of D-amino acids like DPA are as yet unclear, there are suggestions that DPA, in particular, may have pharmacological activity.
The DL-phenylalanine form is thought to possess both
analgesic and antidepressant capabilities, possibly through its ability to block the degradation of the endorphin
enkephalin by the enzyme carboxypeptidase A.
As a precursor of DL-phyenylalanine, L-phenylalanine (the most common form) has been shown to have a role in the synthesis of norepinephrine and dopamine, and elevated cerebral levels of these neurotransmitters has been thought to be associated with antidepressant effects. Basically, L-phenylalanine is converted into L-tyrosine, a DNA-encoded amino acid which is converted by the body’s chemistry into L-DOPA, which in turn is converted into the catecholamines dopamine, norepinephrine (or noradrenaline) and epinephrine (or adrenaline).
DL-phenylalaline is also being used to help with memory and learning, as an appetite suppressant, and in the treatment of Parkinson’s disease and chronic arthritic pain, although rigorous clinical trials for these applications are still in short supply.
Aspartame, marketed under trade names including Equal and Nutrasweet – popular sugar-replacements widely used in weightloss products, and in more than 6,000 consumer food and beverages worldwide – is an attractive sweetener because it is 180 times sweeter than sugar. This means that, compared to sugar, the amount of product required to produce a similarly sweet taste is calorically insignificant. First synthesized by chemists from G.D. Searle and Co. in 1965, aspartame was not approved by the FDA for use as a food additive until 1980, largely due to unanswered questions about a correlation with cancer incidence in rats discovered during testing. Following FDA approval for use in dry goods, aspartame was further approved for use in carbonated beverages, with all other restrictions being dropped by 1996. Numerous other investigations, in Europe and elsewhere have been conducted, all with similar results. Juliette Kellow, a dietician with Weight Loss Resources U.K. (billed as an 'online slimming club', and hence presumably in business to sell weight loss techniques and supplements), says: “more than 200 objective scientific studies have shown aspartame to be completely safe. Its safety has been confirmed by the regulatory authorities in more than 100 countries including the European Commission’s Scientific Committee for Food, America’s Food and Drug Administration and by experts within the United Nation’s Food and Agriculture Organisation and the World Health Organisation.”
However, she notes, despite this confidence level, aspartame products are still required to carry a public notice identifying that they contain phenylalanine. This is because, while Phe is safe for the general public, there are people with a rare genetic disorder called phenylketonuria who are unable to properly metabolize phenylalanine and so are required to limit their intake of Phe from any source – including aspartame. Accordingly, all products in the U.S. and Canada that contain aspartame must be labelled: "Phenylketonurics: Contains phenylalanine."
Katherine Zeratsky, a dietician with the Mayo Clinic, agrees, saying:
“Phenylalanine is safe to eat or drink unless you have phenylketonuria (PKU), a rare birth defect in which an enzyme needed to process phenylalanine is missing. For infants and children with this disorder, consuming phenylalanine is dangerous. Adults with this disorder should consult their doctors regarding whether phenylalanine is a concern. If you do not have PKU, phenylalanine in foods is not a concern.”
Recently, researchers have found a way in which even those with PKU can consume phenylalanine with much less risk. BioMarin Pharmaceutical, a California company, was granted FDA approval on December 13, 2007 for its newly developed drug, Kuvan , which trials suggest helps people with PKU to ingest phenylalanine in 30-50% of cases.
So, say dieticians, aside from concerns voice by relatively fringe elements, there appear to be few reasons not to take phenylalanine. But are there any good reasons?
As it turns out, there is very little research pointing to the beneficial aspects of Phe – the analgesic and anti-depressant effects mentioned earlier. While some anecdotal reports suggest there is a link between Phe intake and elevated (and beneficial) dopamine, norepineprhine and epinephrine levels, insufficient data exists to posit a solid causal link. And, in the case of Phe use for treatment of arthritis, Parkinson’s or for memory support, data is even more scant. From all indications, a balanced diet high in protein would appear to provide the same benefits.
But on the other hand, how could it hurt?