Overview:

Lysine, or L-lysine, is an essential amino acid. That means it is necessary for human health, but the body can't manufacture it. You have to get lysine from food or supplements. Amino acids like lysine are the building blocks of protein. Lysine is important for proper growth, and it plays an essential role in the production of carnitine, a nutrient responsible for converting fatty acids into energy and helping to lower cholesterol. Lysine appears to help the body absorb calcium, and it plays an important role in the formation of collagen, a substance important for bones and connective tissues including skin, tendon, and cartilage.

Most people get enough lysine in their diet, although athletes, vegans who don't eat beans, as well as burn patients may need more. Not enough lysine can cause fatigue, nausea, dizziness, loss of appetite, agitation, bloodshot eyes, slow growth, anemia, and reproductive disorders. For vegans, legumes (beans, peas, and lentils) are the best sources of lysine.

Uses:

Herpes Simplex Virus (HSV)

Some studies have found that taking lysine on a regular basis may help prevent outbreaks of cold sores and genital herpes. Lysine has antiviral effects by blocking the activity or arginine, which promotes HSV replication. One review found that oral lysine is more effective for preventing an HSV outbreak than it is at reducing the severity and duration of an outbreak. One study found that taking lysine at the beginning of a herpes outbreak did not reduce symptoms.

Osteoporosis

Lysine helps the body absorb calcium and decreases the amount of calcium that is lost in urine. Because calcium is crucial for bone health, some researchers think lysine may help prevent bone loss associated with osteoporosis. Lab studies suggest that lysine in combination with L-arginine (another amino acid) makes bone building cells more active and enhances production of collagen. But no studies have examined whether lysine helps prevent osteoporosis in humans.

Dietary Sources:

Foods rich in protein are good sources of lysine. That includes meat (specifically red meat, pork, and poultry), cheese (particularly parmesan), certain fish (such as cod and sardines), nuts, eggs, soybeans (particularly tofu, isolated soy protein, and defatted soybean flour), spirulina, and fenugreek seed. Brewer's yeast, beans and other legumes, and dairy products also contain lysine. Many nuts also contain lysine along with arginine (lysine counteracts some of the effects of arginine). So if someone is trying to eat a diet rich in lysine to prevent HSV outbreaks, nuts would be a good choice.

Available Forms:

Lysine is available in tablets, capsules, creams, and liquids, and is usually sold in the L-lysine form.

How to Take It:

Pediatric

Speak with your pediatrician regarding appropriate dosages. Dose is usually adjusted based on body weight.

Adult

For adults ages 13 and older: Recommendations are 12 mg/kg/day.

An example of a dose often used during an active herpes flare up is 3,000 - 9,000 mg/day in divided doses for a short period of time. To prevent recurrences, many people take 1,000 mg daily. However, dosing depends on many different factors and you should talk to your doctor to determine the right dose for your particular situation.

Precautions:

Because of the potential for side effects and interactions with medications, you should take dietary supplements under the supervision of a knowledgeable health care provider.

Lysine in the diet is considered safe. High doses have caused gallstones. There have also been reports of renal dysfunction, including Fanconi's syndrome and renal failure.

People with kidney or liver disease should ask their doctor before taking supplemental lysine.

Pregnant and breastfeeding women should not take supplemental lysine without talking to their doctor.

Possible Interactions:

If you are currently being treated with any of the following medications or supplements, you should not use lysine supplements without first talking to your health care provider.

Arginine -- Arginine and lysine share common pathways in the body. High levels of arginine may lower lysine levels in the body.

Aminoglycoside antiobiotics (gentamicin, neomycin, streptomycin, etc.) -- Use with lysine may increase the risk of nephrotoxicity.

Alternative Names:

Amino acid K; L-lysine