Lysine, or L-lysine, is an amino acid that serves as a building block of protein. It is classified as an essential amino acid, meaning the body cannot produce it. Instead, it must be obtained from dietary sources. Lysine is necessary for processes like normal growth and muscle tissue turnover.
The Role of Lysine in the Body
As a component of protein, lysine is involved in the growth and repair of body tissues, including the synthesis of proteins that make up muscle. The body also utilizes lysine to produce collagen, a structural protein that provides the framework for skin, bones, and connective tissues like tendons.
Lysine is also a precursor to carnitine, a substance in cells responsible for transporting fatty acids into the mitochondria to be burned for energy. Insufficient lysine can impair carnitine production and affect energy metabolism. Lysine also aids in the absorption of calcium from the intestine and helps the kidneys hold onto this mineral, contributing to bone health.
Lysine in Your Diet
Lysine is available in a variety of foods, particularly those high in protein. Animal-based products are among the richest sources and contain complete proteins, providing all essential amino acids. These sources include red meat, poultry like chicken, fish such as cod and sardines, eggs, and dairy products.
For individuals following plant-based diets, several options contain significant amounts of lysine. Legumes are a primary source, with reliable choices including:
- Lentils
- Chickpeas
- Black beans
- Soybeans, tofu, and tempeh
Other plant-based foods that provide lysine include quinoa, nuts, and seeds. While most people get enough lysine through a balanced diet, those on strict vegan diets with limited protein variety may have a higher risk of deficiency.
Common Uses for Lysine Supplements
One of the most common uses for lysine supplements is managing cold sores, caused by the herpes simplex virus type 1 (HSV-1). The theory is that lysine interferes with arginine, an amino acid the virus needs to replicate. By blocking arginine, lysine may help prevent the virus from multiplying, potentially reducing the frequency and duration of outbreaks. Research suggests daily doses over 3 grams may be more effective for this purpose.
Lysine may also help reduce anxiety. Studies suggest it can act on receptors involved in the stress response, with research showing that supplementing with lysine and arginine helped lower stress-induced anxiety and cortisol levels. This may work by partially blocking serotonin receptors in the intestine, which influences the gut-brain axis.
Because lysine promotes calcium absorption and collagen synthesis, it is also used to support bone health. By helping the body absorb and retain calcium, it may help maintain bone density. Studies on individuals with osteoporosis showed that lysine supplementation helped reduce the amount of calcium lost through urine.
Dosage and Potential Side Effects
Lysine supplement dosage varies depending on the intended use. For general health, a dietary intake of around 1 gram per day is common. To manage cold sores, studies have used doses ranging from 300 milligrams to 3 grams daily, though some sources suggest doses over 3 grams are needed during an active outbreak.
Lysine is considered safe for most people at recommended doses for up to one year. High doses can cause side effects, most commonly digestive issues like stomach cramps, diarrhea, and nausea. Doses between 10 and 15 grams a day are more likely to cause these effects.
People with kidney or liver disease should consult a doctor before taking lysine, as high levels of single amino acids can put additional strain on these organs. Because lysine increases calcium absorption, those taking calcium supplements should also speak with a healthcare provider to avoid excessively high calcium levels. There is not enough reliable information on the safety of lysine supplements during pregnancy or breastfeeding, so avoidance is recommended.