Product Reviews
Lysine Supplements Review

Initial Posting: 2/6/16

Lysine Supplements Reviewed by Sections: Jump to a section by clicking on its name.
  • Lysine (L-lysine) is an essential amino acid found in many protein-rich foods (see Lysine in Food) and is needed for proper growth and other critical functions (see details in What It Is).
  • As a supplement, lysine may help prevent cold sores (herpes simplex labialis), genital herpes lesions, and canker sores. Although it is also found in topical products for cold sores, it is not known to be active topically (See details in What It Does).
  • Typical daily dosage is 1,000 to 3,000 mg (see details in Quality Concerns).
  • Lysine has also been used to prevent/treat feline herpesvirus 1 infection — but there is no clinical evidence to support this use and it is not recommended (see details in What It Does, For Cats).
  • CL's tests found that all but one product contained their listed amounts of lysine (see details in What CL Found).
  • Best value: The cost to obtain lysine from CL Approved products ranged from 4 cents to 33 cents per 1,000 mg (and up to 72 cents for cat products). See which CL Approved products provide the best value.
  • To compare product test ratings, ingredients, and prices, see the Results Table.
  • People with kidney disease, gallstones, elevated cholesterol, and glutaric acidemia type I should exercise caution with lysine supplements (see details in Concerns and Cautions).
What It Is:
Lysine is an essential amino acid, meaning that it must be obtained from foods, because the body is unable to make it. It is important for proper growth, and is involved in the production of collagen as well as calcium absorption. Most people need about 1 gram per day, which can typically be provided by a 100 gram (3.5 oz) serving of protein rich food such as beef or poultry, eggs or cheese. Vegetarian sources include tofu, beans, nuts such as peanuts and almonds, and sunflower seeds. (See Lysine in Foods table below for amounts found in individual foods.) 

What It Does:
Herpes simplex virus (cold sores and genital herpes)
Some, but not all studies, suggest that taking between one to three grams of lysine from supplements daily may help to reduce the occurrence and severity of cold sores (herpes simplex labialis). Lower doses may not be effective.

A small double-blind, placebo-controlled study in men and women with recurrent cold sores or genital herpes lesions found those who took tablets providing one gram of L-lysine monohydrochloride three times daily (a total daily dose of 3 grams) for six months had an average of 2.4 fewer cold sore or genital lesion outbreaks, as well as a significant reduction in symptom severity and healing time, compared to placebo (Griffith, Dermatologica 1987). Another small study reported that taking a little over one gram of L-lysine monohydrochloride daily reduced the recurrence rate of cold sores, although it did not shorten healing time compared to placebo (McCune, Cutis 1984). The study also reported that a lower dose (a little over half a gram per day) did not have an effect. However, another double-blind study found no reduction in the recurrence of cold sores or rate of healing compared to placebo during three months of daily supplementation with 1 gram of L-lysine-monohydrochloride (Milman, Acta Derm Venereol 1980).

A small cross-over study among people with recurring cold sores had mixed results: it found that those who took 1 gram of L-lysine monohydrochloride daily for six months did not have significantly fewer cold sores compared to placebo; however, during the next six months when participants switched and took the treatment they did not take during the first six months (either lysine or placebo), those who took lysine did have significantly fewer cold sores (1.8 versus 2.9) compared to placebo (Thein, Oral Surg Oral Med Oral Pathol 1984). The study also reported that the number of cold sores was associated with blood levels of lysine, with occurrences reduced in those with blood levels of lysine above 165 nmol/ml.

There are no studies on the effect of lysine in treating an existing herpes eruption.

Laboratory research suggests that lysine may help to inhibit the herpes simplex virus by blocking arginine, an amino acid needed by the virus to replicate; therefore, it has been theorized (but not proven) that limiting intake of foods high in arginine (such as chocolate, peanuts, other nuts and seeds) may be helpful if trying to prevent a herpes eruption (Griffith, Chemotherapy 1981). However, there is no evidence that eating these foods triggers a herpes eruption.

Canker sores
One study reported that 400 mg of lysine daily may help to prevent canker sores, while a dose of 4 grams daily may decrease healing time for canker sores (aphthous ulceration) — which are suspected, but not proven, to be associated with the herpes simplex virus (Wright, Gen Dent 1994). A small placebo-controlled study among people with recurring canker sores found that 62.5% of those who took 2 tablets of lysine daily with meals (Herpetrol, Alva-Amco Pharmacal Cos., Inc.) providing a daily total of 630 mg of L-lysine monohydrochloride reported a decrease in the recurrence of canker sores, while just 14% of the placebo group experienced a decrease (Ozden, J Exp Integr Med 2001). However, among those taking lysine who did develop a canker sore, symptoms (itching, burning, and redness) and duration were not improved. Herpetrol no longer appears to be available as a dietary supplement; it is now sold as a topical gel with other ingredients.

Calcium absorption
Lysine supplementation may increase calcium absorption, as demonstrated in short-term studies of women with osteoporosis given 400 mg and 800 mg of L-lysine (Civitelli, Nutrition 1992).

Topical lysine
Lysine is available in several topical products (gels and creams) for cold sore relief, typically in combination with other ingredients. Although "lysine" is often in the name of these products, it is actually not an "active" ingredient and there is no good clinical evidence that these topical products are effective.

For example, topical gels such as Herpetrol and Lysimax (both by Alva-Amco Pharmacal Co., Inc.) include benzalkonium chloride (an antiseptic), menthol (an analgesic), and only list an unspecified amount of lysine HCL as an "inactive ingredient." Similarly, a cream, SuperLysine Plus+ from Quantum Health Inc., lists menthol as the active ingredient, and only includes lysine as an inactive ingredient, along with a many other ingredients, such as beeswax. A study funded by the maker of this product found that among people with a recent eruption of a cold sore who applied the cream every two hours, 40% reported full resolution of the sore by the third day and 87% by the end of the sixth day (Singh, Altern Med Rev 2005). However, this study did not include a placebo, making the results of questionable value.

For cats
Feline herpesvirus 1 is a highly contagious virus that affects many cats, causing flu-like signs and irritation of the eye and nose. Lysine supplementation has been popularly used to prevent and treat these infections. However, a comprehensive review of evidence in 2015 concluded that there is a "complete lack of any scientific evidence for its efficacy" and recommended against its use (Bol, BMC Veterinary Research 2015).

Quality Concerns and What CL Tested For:
Neither the FDA nor any other federal or state agency routinely tests lysine supplements for quality prior to sale., as part of its mission to independently evaluate products that affect health, wellness, and nutrition, purchased several dietary supplements sold in the U.S. claiming to contain lysine. These were tested for their amount of lysine. Standard tablets and caplets were also tested for their ability to properly disintegrate ("break apart") as needed for absorption.

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