Herbs & Supplements:

Lysine

Lysine is an essential amino acid, one that you need to get from food. Some evidence suggests that supplemental lysine may be able to help prevent herpes infections (cold sores and genital herpes).

Requirements/Sources

Most people need about 1 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 is 1 g 3 times daily. You can take this as a regular part of your diet in hopes of preventing herpes flare-ups, or, perhaps, at the first sign of an attack. Although the evidence isn't strong, there may be some advantage to restricting your 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 herpes flare-ups, although other studies have not found benefit.^1–6 Lysine has also been proposed as a treatment to take at the onset of a herpes attack, but at least one study failed to find it effective for this purpose.⁷

Both cold sores and genital herpes are caused by a virus called herpes simplex. After you are first infected, this virus hides in certain nerve cells, and reemerges under times of stress. Test tube research suggests that lysine fights this virus by blocking arginine, an amino acid the virus needs in order to replicate.⁸For this reason, lysine might be most effective when used in conjunction with a low-arginine diet.

What Is the Scientific Evidence for Lysine?

Herpes Simplex

When taken in sufficient doses, it appears that regular use of lysine supplements might be able to reduce the number and intensity of herpes flare-ups.⁹ However, a study evaluating lysine taken only at the onset of a herpes attack found no benefit.¹⁰ (Consider using melissa for this latter purpose.)

One double-blind placebo-controlled study followed 52 participants with a history of herpes flare-ups.¹¹ While receiving 3 g of L-lysine every day for 6 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 41 subjects also found improvements in the frequency of attacks.¹² Interestingly, this study found that 1,250 mg of lysine daily worked, but 624 mg did not.

Other studies, including one that followed 65 individuals, found no benefit, but they used lower dosages of lysine.^13,14

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

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,^15,16 so you may want to use caution when using lysine if you have either of these problems. Maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established.

Interactions You Should Know About

If you are taking lysine to treat herpes, arginine might counteract the potential benefit.¹⁷

Last reviewed March 2002 by Medical Review Board

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