Lysine is an essential amino acid therefore it must be obtained from the diet as the body cannot produce its own. It is an essential building block for all protein in the body and can be found in animal meats, fish, dairy products, legumes and brewer's yeast. It performs many useful functions in the body and has proved to be especially useful in treating herpes and cold sores. Lysine also increases the absorption of calcium so it may help to prevent and treat osteoporosis.

To the bodybuilder, lysine offers many benefits:

1. It helps build muscle protein.

2. It helps maintain nitrogen levels.

3. It supports the production of hormones.

4. It speeds up recovery from injury or overtraining.

Although lysine can be readily obtained from many foodstuffs, supplementation can enhance the effects noted above. No problems have been reported with normal usage but high doses exceeding 15 grams can cause stomach problems and cramp.