ever wondered why?

ever wondered what this label is for?and why is it present at the back of a diet coke? if no, let me explain it to u.

these products i.e, diet coke & several others contains aspartame which is an artificial sweetener.It is 180 times as sweet as sugar in typical concentrations, without the high energy value of sugar. While aspartame, like other peptides, has a caloric value of 4 kilocalories (17 kilojoules) per gram, the quantity of aspartame needed to produce a sweet taste is so small that its caloric contribution is negligible, which makes it a popular sweetener for those trying to avoid calories from sugar.

Aspartame is composed of two amino acids, aspartic acid and phenylalanine.

so now we should know a bit of phenylketonuria:

• Phenylketonuria (PKU) is a rare, inherited metabolic disease that results in mental retardation and other neurological problems when treatment is not started within the first few weeks of life.
• cause-The disease arises from the absence of a single enzyme (phenylalanine hydroxylase). This enzyme normally converts the essential amino acid, phenylalanine, to another amino acid, tyrosine. Failure of the conversion to take place results in a buildup of phenylalanine. Through a mechanism that is not well understood, the excess phenylalanine is toxic to the central nervous system and causes the severe problems normally associated with PKU.
• The diet for the most severe form of phenylketonuria eliminates all of the very high protein foods since all protein contains phenylalanine. This means that all concentrated sources of protein must be eliminated from the diet in order to limit the amount of phenylalanine. Except in rare circumstances, the diet does not allow consumption of meat, fish, poultry, milk, eggs, cheese, ice cream, legumes, nuts, or many products containing regular flour. A synthetic formula is used as a nutritional substitute for the eliminated foods.
  

now coming back to aspartame-this sugar substitute, sold commercially as Equal and NutraSweet, was hailed as the savior for dieters who for decades had put up with saccharine's unpleasant after taste. but this,as u now know contains phenylalanine,so people with phenylketonuria when they consume products with aspartame will have increased blood levels of phenylalanine {since they cannot metabolise it} .Toxic levels of this substance in the blood can result in mental retardation.

Since individuals with PKU must consider aspartame as an additional source of phenylalanine, aspartame-containing foods must state “Phenylketonurics: Contains Phenylalanine”