- Training Reference Notes

Health and nutrition education and training for Quest stockists and consumers.

Produced by the Nutrition Department, Quest Vitamins Limited,
Birmingham, B7 4AP, Tel: 0121 359 0056, Fax 0121 359 0313, e-mail:
© Quest Vitamins Ltd. 2001 - No reproduction of material without permission from Quest Vitamins Ltd.



L-lysine is an essential amino acid that occurs naturally as part of food proteins and cannot be manufactured by the body. It is usually the limiting factor in the biological availability of vegetable proteins and this means that vegetarians (and especially vegans) have to plan their diets carefully in order not to suffer from a deficiency of L-lysine.


L-lysine is an important structural component of many proteins. It is also directly involved in the production of L-carnitine, which is required for the transport, and utilisation of fats.

Lysine is needed to make the non-essential amino acid, carnitine, involved in fat transportation.

Two other roles in which L-lysine is involved are retention of Calcium within the body and maintenance of the Immune System (1).


Cold Sores:
One of the main uses of L-lysine is as a weapon against the Herpes simplex virus, which causes cold sores.
L-lysine is an antagonist of L-arginine, and L-arginine is known to feed the Herpes simplex virus. Oral doses of between 300 and 1200mg of L-lysine are thought to be effective (1).

L-lysine supplements may be necessary for vegans or vegetarians, especially if they have neither dairy products nor legumes included in their diet. Fruit and vegetables contain very little lysine (2).

The amino acid may also be a good adjunct nutrient in preventing against Osteoporosis (3), because when L-lysine is deficient, more calcium is lost in the urine.


Toxicity of L-lysine has not been reported with levels as high as 8g per day.


There are no known drug interactions or other contra-indications for L-lysine.

N.B. L-lysine is unstable and has to be presented as L-lysine hydrochloride (HCl) in supplements.


1. Flodin NW. The metabolic roles, pharacology, and toxicology of lysine. J Am Coll Nutr, 16;1:7-21 1997.
2. "The Healing Nutrients Within", E R Braverman & C C Pfeiffer, Keats, 1987.
3. Fürst P. Dietary L-lysine supplementation: a promising nutritional tool in the prophylaxis and treatment of Osteoporosis. Nutrition, 9;1:71-72 1993.