Lysine is an essential amino acid vital for numerous physiological functions, including growth, tissue repair, and collagen production. As the body cannot synthesize lysine, it must be obtained through diet or supplementation. 

Lysine plays a crucial role in carnitine production, which aids in converting fatty acids into energy and lowering cholesterol levels. 

It enhances wound healing by promoting cell proliferation and angiogenesis, supports the absorption of calcium, iron, and zinc, and is involved in enzyme, antibody, and hormone production. 

Additionally, lysine strengthens the immune system, exhibits antimicrobial properties against Clostridium difficile, and helps prevent herpes outbreaks. 

Adequate lysine intake is essential for athletes, burn victims, and vegans, who may be at risk for deficiency. 

Rich dietary sources of lysine include red meat, poultry, fish, dairy products, soy products, nuts, and certain grains like whole wheat. 

However, excessive amino acid supplementation can lead to side effects such as abdominal cramps, diarrhea, and increased risk of gallstones, and may pose risks for individuals with liver or kidney disease.

What is Lysine? [9.] 

Lysine is an essential amino acid that the human body cannot produce on its own and must be obtained through diet or supplementation.

Lysine is essential for many normal physiological functions, including:

• Growth and tissue repair: lysine is crucial for the growth and repair of body tissues, including skeletal muscle. [2., 16.]  

• Carnitine production: lysine plays an essential role in the production of carnitine, a nutrient responsible for converting fatty acids into energy and helping lower cholesterol. [8.] 

• Wound healing: lysine enhances wound healing in both acute and chronic wounds by promoting cell proliferation and angiogenesis. [2.] 

• Absorption of calcium, iron, and zinc: lysine supports the absorption of these minerals. [7.]

• Collagen production: lysine promotes collagen growth. [16.] 

• Enzyme, antibody, and hormone production: lysine assists in the production of these essential proteins. [5., 7.] 

• Supporting the immune system: lysine bolsters the immune system. [2.] 

• Antimicrobial action: lysine inhibits the growth and toxin production of Clostridium difficile [2.] 

• Prevents herpes outbreaks: A typical therapeutic dosage of L-Lysine may be 1 g three times per day or more for 6 months, to reduce the likelihood of herpes outbreaks. [7.] 

Daily Lysine Requirements and Signs of Deficiency [9.] 

Studies using the nitrogen balance method and whole-body oxidation rates suggest that the lysine requirement for adults might be around 35 mg/kg per day.

Protein deficiency, which includes a lack of essential amino acids like lysine, can lead to symptoms such as poor musculature, edema, and skin lesions, although severe deficiency is rare in the United States.

Athletes, burn victims, and vegans may be at greatest risk for lysine or protein deficiency. 

Health Benefits of Lysine

Lysine Benefits

Lysine plays a crucial role in protein synthesis, contributing to the growth and maintenance of tissues throughout the body. It is particularly important for proper growth and development in children. 

Additionally, lysine has benefits in promoting wound healing, optimizing mineral absorption, and supporting immune function.

Because of its benefits in optimizing calcium absorption, it may indirectly benefit bone health. 

One study also demonstrated that lysine may be protective to the kidneys in the setting of salt-sensitive hypertension: researchers discovered that lysine metabolism accelerates in hypertensive rats, primarily through N-alpha degradation, and that lysine administration reduces hypertension and kidney injury. [12.] 

Protective mechanisms include diuresis, inhibition of tubular albumin uptake, and formation of new metabolites like Nε-malonyl-lysine, which reduces fatty acid synthesis. [12.] 

Lysine also depletes central carbon metabolites, supporting kidney health. However, this study should be interpreted cautiously when considering lysine as a medical intervention.  

L-lysine may also reduce hyperglycemia in the setting of type 2 diabetes. [4.] 

Foods High in Lysine

Lysine is found in a variety of food sources, both plant-based and animal-based. Some of the richest sources of lysine include red meat, poultry, fish, dairy products, soy products, nuts, and certain grains like whole wheat. [8.] 

Beans, peas and lentils may be appropriate sources of lysine for vegetarians and vegans. 

Incorporating these foods into a balanced diet can help ensure adequate lysine intake.

Testing Lysine Levels

Test Information, Sample Collection and Preparation

Amino acids including lysine may be tested in blood or urine. Blood tests require a venipuncture, while urine samples may be collected from the comfort of home. 

Fasting is generally required prior to sample collection. It is important to consult with the ordering provider prior to sample collection to determine whether certain supplements should be avoided. 

Plasma vs. Urine Assessment of Amino Acids

Plasma amino acid testing and urine amino acid testing are both valuable diagnostic tools used to assess amino acid metabolism and provide insights into various aspects of health. However, each method offers distinct advantages. 

Plasma amino acid testing involves the analysis of amino acid levels in the bloodstream, offering real-time information about amino acid concentrations and their role in metabolic processes. 

This method provides a snapshot of amino acid status and allows clinicians to identify immediate metabolic dysregulation, amino acid deficiencies, and imbalances in metabolic pathways. 

Additionally, plasma amino acid testing enables the evaluation of amino acid levels associated with neurotransmitter synthesis, providing insights into neurotransmitter balance and cognitive health. [10.]  A plasma sample is also recommended when kidney function is compromised.

Recent food intake briefly elevates plasma levels, making fasting samples preferable. While short-term fasting doesn't deplete plasma amino acids, long-term malnutrition does. 

Despite good correlation between plasma and urine amino acids, urine samples represent recent dietary intake and metabolism, offering insight into fluctuating diets or controlled dietary changes. 

Urine samples, collected conveniently at home, are suitable for assessing controlled diets or recent dietary modifications, although results are influenced by kidney function, with biomarkers ratioed to urine creatinine.

In contrast, urine amino acid testing offers a comprehensive view of amino acid excretion and metabolic waste products.  [11.]   

While urine amino acid testing may not provide real-time information about amino acid concentrations in the bloodstream, it offers valuable insights into amino acid metabolism and renal function.

Urine amino acid testing is often used to screen for inborn errors of amino acid metabolism, although it is also used in assessing long-term metabolic health and monitoring treatment responses over time. [1.]

Interpreting Lysine Test Results

Optimal Levels of Lysine

Lysine levels should be interpreted within the context of an individual’s full medical history, depending on the sample type used. 

One laboratory company recommends a plasma lysine level between 210.6 - 498.2

nmol/mL. [14.] 

Another laboratory company recommends a urine lysine level between 11-175 micromol/g creatinine. [15.] 

Clinical Significance of Excessive Lysine Levels

Although rare, excessively high lysine levels may indicate excessive supplementation or decreased metabolism and utilization of lysine. 

Excessive lysine levels may also be related to kidney dysfunction, as buildup of amino acids can increase the total body nitrogen load, leading to ammonia buildup and impair kidney function. This is due to the known relationship between chronic kidney disease and excessive protein intake. [6.] 

Excessive lysine may also be associated with acute renal failure. [13.] 

Clinical Significance of Decreased Lysine Levels

Decreased lysine levels may be associated with malnutrition or poor protein intake, or digestive insufficiency. In urine tests, low levels of amino acids such as lysine may signal kidney disease. 

Safety Considerations

While lysine offers various health benefits, it is essential to be aware of potential side effects and safety considerations associated with its consumption or supplementation.

Lysine Side Effects

In general, lysine is considered safe when consumed in moderate amounts through dietary sources. 

However, excessive intake of amino acid supplements may lead to side effects such as abdominal cramps, diarrhea, and increased risk of gallstones. [3.] 

Additionally, individuals with certain medical conditions, such as liver or kidney disease, should exercise caution and consult with a healthcare professional before taking amino acid supplements. [3.] 

Individuals on medications, pregnant or breastfeeding women, and people with kidney issues  should also consult with their healthcare providers before taking lysine or amino acid supplements.

FAQ: Lysine as a Biomarker

Lysine is an essential amino acid that plays a crucial role in various physiological functions. It is important for protein synthesis, calcium absorption, and the production of hormones, enzymes, and antibodies. In this FAQ section, we answer common questions related to lysine, its benefits, sources, and precautions.

What is Lysine Good For?

Lysine is good for promoting healthy growth and development, improving calcium absorption, aiding in collagen formation for healthy skin, and supporting the immune system. 

It is also beneficial in the prevention and treatment of cold sores caused by the herpes simplex virus.

How Much Lysine Should I Take?

The recommended daily intake of lysine varies depending on age, sex, and overall health. 

On average, adults should aim for about 30-35 mg per kilogram of body weight per day.

Doses for herpes simplex management may be different; one resource recommends doses as high as 1 gram 3 times a day for at least 6 months.  

However, it is best to consult with a healthcare provider to determine the appropriate dosage for your specific needs.

What Does Lysine Do?

Lysine plays several critical roles in the body. It helps in the formation of collagen, supports the immune system, aids in the absorption of calcium, and is involved in the production of carnitine, which is essential for converting fatty acids into energy.

What Foods Have Lysine?

Lysine is found in high-protein foods. Good sources include meat, fish, dairy products, beans, lentils, and certain grains like whole wheat. Incorporating these foods into your diet can help ensure you get an adequate amount of lysine.

How Much Lysine is Too Much?

While lysine is generally safe when taken in recommended amounts, excessive intake can lead to side effects such as stomach pain, diarrhea, and kidney issues. It is important not to exceed the dosage recommended by a healthcare provider.

Who Should Not Take Lysine?

Individuals with certain health conditions should avoid taking lysine supplements without consulting a healthcare provider. 

These include people with kidney disease, those who are pregnant or breastfeeding, and individuals with a history of lysine metabolism disorders.

If you have any other questions about lysine, feel free to reach out to a healthcare professional for personalized advice.

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