Does L Lysine Work?

Lysine, or L-lysine, is one of many different amino acids your body needs to build protein. It plays an important role in normal growth, and in the conversion of fat into energy. L-lysine helps with maintenance of bones, skin and connective tissue. Clinical studies measuring supplemental L-lysine's ability to prevent or treat cold sores -- or herpes simplex outbreaks -- have shown conflicting results. Speak with your doctor if you are considering taking L-lysine supplements to prevent or heal herpes simplex infection, or for any other reason.

Function

It is not fully understood how or if lysine helps reduce the occurrence and severity of cold sores. It might be due to L-lysine's ability to block the action of another amino acid -- known as arginine -- according to New York University Langone Medical Center. The herpes simplex virus requires arginine to reproduce itself.

Evidence

One study published in a 1984 issue of "Archives of Dermatology" found no evidence that taking 400 mg of L-lysine -- three times a day -- reduces the frequency, duration or severity of herpes simplex outbreaks. A later study, published in "Dermatologica," found that treatment with 1,000 mg supplements of L-lysine -- three times a day for six months -- reduced the occurrence, severity and healing time in people with recurrent herpes simplex infection.

Diet

L-lysine is found naturally in foods that are high in protein. Some of the best sources of L-lysine include beef, pork, chicken, turkey, cheese and eggs. It is found in soy products such as tofu, and in the isolated soy protein used to make vegetarian meat substitutes. Dried beans, nuts and dairy products supply L-lysine.

Supplements

The therapeutic dose of L-lysine supplements that might help reduce the occurrence or healing time of herpes simplex is 1 g, three times each day, either regularly or at the first sign of a cold sore. This finding was reported by New York University's Langone Medical Center. A study published in "Alternative Medicine Review" in 2005 found that a topical ointment containing lysine, zinc and herbs is effective in reducing cold-sore healing time.

Warnings

Although L-lysine is a safe, natural part of most people's diets, no clinical studies have been performed to determine the safety of high concentrations found in supplements. Animal studies have found that high doses of L-lysine might cause gallstones and increase blood cholesterol levels. Maximum safe doses have not been established for pregnant or nursing women, children or people with chronic diseases. Tell your doctor if you are taking L-lysine supplements for any reason.