What is lysine as a therapeutic supplement?

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Natural substance of the human body used as a supplement to treat specific health conditions.
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Lysine is an essential amino acid that is obtained from food. Some evidence suggests that supplemental lysine may be able to help prevent herpes infections such as cold sores and genital herpes.

Requirements and Sources

Most people need about 1 gram (g) of lysine per day. The requirement may be greater for athletes and people recovering from major injuries, especially burns. The richest sources of lysine are animal proteins such as meat and poultry, but it is also found in dairy products, eggs, and beans.

Therapeutic Dosages

A typical therapeutic dosage of lysine for herpes infections is 1 g three times daily. Lysine can be taken as a regular part of the diet in hopes of preventing herpes flare-ups, or, perhaps, at the first sign of an attack. Although the evidence is not strong, there may be some advantage to restricting the intake of foods that contain a lot of arginine, such as chocolate, peanuts, other nuts and seeds, and, to a lesser extent, wheat.

Therapeutic Uses

Some small studies suggest that regular use of lysine supplements can help prevent flare-ups of cold sores and genital herpes, although other studies have not found any benefit. Lysine has also been proposed as a treatment to take at the onset of a flare-up, but at least one study failed to find it effective for this purpose.

Both cold sores and genital herpes are caused by a virus called herpes simplex. After a person is first infected, this virus hides in certain nerve cells and reemerges during times of stress. Test-tube research suggests that lysine fights this virus by blocking arginine, an amino acid the virus needs to replicate. For this reason, lysine might be most effective when used in conjunction with a low-arginine diet. However, this widely stated claim has not been proven. (Note that if this were true, people who have herpes would need to avoid taking arginine supplements.)

Scientific Evidence

It appears that regular use of lysine supplements, when taken in sufficient doses, might be able to reduce the number and intensity of herpes flare-ups. One double-blind, placebo-controlled study followed fifty-two participants with a history of herpes flare-ups. While receiving 3 g of L-lysine every day for six months, the treatment group experienced an average of 2.4 fewer herpes flare-ups than the placebo group, a significant difference. The lysine group’s flare-ups were also significantly less severe and healed faster.

Another double-blind, placebo-controlled crossover study on forty-one subjects also found improvements in the frequency of attacks. This study found that 1,250 milligrams (mg) of lysine daily worked, but 624 mg did not. Other studies, including one that followed sixty-five individuals, found no benefit, but they used lower dosages of lysine.

Although some of these studies are promising, none of them was large enough to give conclusive answers. At this point, more evidence is needed to determine whether lysine is effective for preventing herpes simplex.

Many people use lysine in a different way: They take it at the onset of a herpes attack. However, a double-blind, placebo-controlled study evaluating this method found no benefit. One should consider using the herb lemon balm instead.

Safety Issues

Although lysine is an essential part of the diet, the safety of concentrated lysine supplements has not been well studied. In animal studies, high dosages have caused gallstones and elevated cholesterol levels, so those persons with either of these problems may want to use caution when using lysine. Maximum safe dosages for young children, pregnant or nursing women, and those with severe liver or kidney disease have not been established. In persons taking lysine to treat herpes, arginine might counteract the potential benefit.


Flodin, N. W. “The Metabolic Roles, Pharmacology, and Toxicology of Lysine.” Journal of the American College of Nutrition 16 (1997): 7-21.