L-tyrosine is a non-essential amino acid that plays a role in the creation of protein. The body can make it from the amino acid phenylalanine but nutritional sources include animal meats, wheat, oatmeal and seafood.

It performs a multitude of important roles in the body including the alleviation of depression, enhancement of thyroid efficiency, strengthening of the immune system, prevention of neurological degeneration and protection of the skin.

Bodybuilders find it useful for several reasons:

1. It offsets the stress and fatigue associated with intensive training.

2. It helps in the retention of muscular protein.

3. It heightens mental alertness thus helping to offset mental fatigue.

With any amino acid supplement overdosing can lead to weakness and nausea so care should be taken in applying small doses and increasing them gradually until an optimum level is reached. Bear in mind that many protein powders and other supplements are fortified with amino acids so check the labels carefully. The manufacturer's instructions should be followed in all instances.