Arginine is a semi-essential amino acid that the body cannot make naturally. It is found in nuts, seeds, chocolate and raisins.

Arginine is used by the body in the execution of many important physiological processes including hormone secretion, output of growth hormone, removal of toxins from the body and enhancement of the immune system. It is also a precursor of nitric oxide which vasodiolates vessels in the body. For this reason arginine is often used to treat conditions such as angina, high blood pressure, cardiac disease, sexual dysfunction and infertility. Recent research has also highlighted arginine's ability to scavenge free radicals, remove bad cholesterol, enhance fat metabolism and regulate salt levels.

There are several reasons why arginine appeals to bodybuilders:

1. It prevents the retention of water under the skin thus minimizing bloating and helping to create a ripped appearance.

2. It helps the body to retain nitrogen that is essential to the muscle building process.

3. Its vasodilating abilities support muscle growth.

4. It enhances protein synthesis.

5. It helps to boost the immune system allowing harder training and minimizing the minor illnesses that come from overtraining.

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.