What Does L-Lysine Do for the Body?

Lysine, also known as L-lysine, is one of 20 amino acids the body uses to build protein and repair tissue. Of these 20, nine — including lysine — are considered "essential," meaning they must be obtained from dietary sources because the human body can't synthesize them, as explained in a June 2020 StatPearls study guide published by Europe PMC.

Lysine has a variety of important effects on the body and can be consumed as a supplement to help combat unpleasant symptoms caused by the herpes virus.

Keep reading to learn more about lysine, and to find out whether or not taking an L-lysine supplement may be helpful for you.

Your body needs the essential amino acid lysine for proper growth and energy production. L-lysine performs many critical roles in the body and has many health benefits.

"Lysine appears to help the body absorb calcium," reports Mount Sinai. It also "plays an important role in the formation of collagen, a substance important for bones and connective tissues including skin, tendons and cartilage."

Calcium is critical for bone development; therefore, lysine has a direct effect on bone health. Research suggests it may help limit bone loss and promote greater bone density.

Lysine is "found in great quantities in muscles, and is associated with muscle mass," reported researchers in the August 2020 issue of the journal ‌Nutrients‌.

The Canadian Academy of Sports Nutrition notes that "lysine ... plays a role in the formation of carnitine, an amino acid that burns fat and can increase endurance in athletes."

Carnitine is "a nutrient responsible for converting fatty acids into energy and helping lower cholesterol," adds Mount Sinai.

Lysine is also a building block of protein — and, as the Cleveland Clinic points out, protein is "a champion for your muscles, helping your body build and maintain them."

Research indicates that lysine supplementation may improve herpes outcomes and help reduce the outbreak of cold sores in people with oral herpes, a viral infection.

According to a study published in the June 2017 issue of the journal ​‌Integrative Medicine,‌ lysine suppresses the body's supply of another amino acid, arginine. The herpes virus needs arginine in order to replicate. Therefore, more lysine means less arginine — and a reduced risk of herpes outbreaks.

This effect appears to be true for the herpes simplex conditions oral herpes and genital herpes as well as herpes zoster (aka shingles). However, higher daily doses of lysine are required to achieve this reduction of herpes symptoms and recurrence rates: Low doses are not effective. A diet low in arginine (found in chocolate, nuts and dairy foods) also seems to be required. More studied are needed.

Cautions Mount Sinai, "Some studies suggest that taking lysine on a regular basis may help prevent outbreaks of cold sores and genital herpes. Others show no improvement. ... But supplementation may reduce recurrences or improve symptoms."

The herpes simplex virus also happens to be the most common cause of the facial nerve disease Bell's palsy, so a high-lysine diet is sometimes recommended as a treatment for that, too. However, more research is needed.

Since your body can't generate lysine, you need to consume lysine-rich foods or supplements to ensure that you're getting enough lysine each day.

Fortunately for us, lysine-rich foods are plentiful. Georgia State University and others identify high-protein foods like poultry, pork, red meat, lamb, eggs, fish and cheese — especially ricotta, cottage cheese and Parmesan — as good sources of lysine.

Plants provide lysine, too. According to MyFoodData.com, legumes are the best vegetable source of lysine, with lima beans, soybeans, lentils and green peas topping the list.

However, the Cleveland Clinic recommends focusing on consuming complete proteins — those that contain all nine essential amino acids, including lysine.

People suffering from outbreaks of herpes or shingles sometimes take lysine supplements to ease their symptoms. As explained previously, lysine can possibly help treat Bell's palsy, cold sores, genital herpes and shingles, all of which are caused by different forms of the herpes virus.

Lysine supplementation is also sometimes recommended for athletes. Before taking lysine supplements, talk to your medical provider.

Lysine deficiency is considered uncommon in the United States, even in vegetarians and people on restricted diets. Therefore, lysine supplementation for dietary reasons is typically not necessary.

People at risk of lysine deficiency are those who rarely eat fresh fruit and vegetables, dairy products or meat, but base most of their dietary intake on heavily processed foods, sugary products and soda pop.

A ‌Current Nutrition & Food Science‌ article published in February 2019 observes that the symptoms of lysine deficiency include anemia, dizziness, fatigue, nausea, loss of appetite and reproductive disorders. Talk to your doctor if you have concerns about lysine deficiency.