Lysine – why must it be supplied through food? Its role in the body, requirements, and sources of lysine
Lysine is an essential amino acid, meaning it cannot be synthesized by the human body and must therefore be supplied from external sources - through the daily diet or, if necessary, in supplement form. Lysine plays many important roles in the human body. It is a component of hormones and antibodies, may support the immune and cardiovascular systems, and is involved in tissue repair as well as improving skin elasticity and condition. What other properties does lysine have? Where can it be found in the highest amounts? How should lysine be used, and is it safe?
Table of contents
- Lysine - what is it?
- Lysine - where is it found?
- Properties and uses of L-lysine
- Lysine and blood pressure
- Lysine, stress hormones, and anxiety
- Lysine and cold sores
- Lysine and calcium absorption
- L-lysine requirements
- Lysine deficiency in the human body
- Lysine - how to use it? When to take it?
- Lysine and vitamin C
- Is lysine harmful? Side effects and contraindications for L-lysine use
Lysine - what is it?
Lysine is an organic chemical compound with the formula C6H14N2O2, belonging to the group of protein-building amino acids. It is an essential amino acid that must be delivered through food, as the human body cannot synthesize it on its own.
Lysine has the ability to bind water molecules and is also a basic amino acid. Moreover, it is considered ketogenic – during its metabolism, compounds necessary for ketogenesis are formed.
Lysine was first isolated from casein in 1889. It is a valuable compound present in most proteins that make up body cells. Due to its structure, lysine is chemically active and easily reacts with other substances.
The biologically active form of lysine is L-lysine, found in living organisms. For this reason, the terms “lysine” and “L-lysine” are often used interchangeably.
Lysine - where is it found?
Lysine can be found in many common foods, but it is most abundant in animal-based products.
Although this compound is present in all proteins except corn protein, its content in grains is low. This means that in developing countries, where the daily diet relies mainly on grain-based products, L-lysine becomes a limiting amino acid, making it harder for the body to utilize other amino acids from food. For this reason, in many parts of the world, lysine is added to grain products to boost their nutritional value.
Sources of L-lysine in food include:
- meat and meat products - all types of meat are good dietary sources of lysine
- cheese - parmesan contains the most L-lysine, but all cheeses, including yellow, blue, and cottage cheese, provide significant amounts
- fish - sardines and cod have the highest L-lysine content, though any fish is a valuable source
- eggs
- milk and dairy products
- dry legumes
- nuts
- avocado
- beets
- tomatoes
- pears
- potatoes
Properties and uses of L-lysine
Lysine is a building block of proteins, including those in muscles and tendons. It may help accelerate muscle mass gain and aid in repairing damaged tissues. In addition, lysine can:
- support joint cartilage production
- participate in nucleotide synthesis – the building blocks of DNA
- play a role in lactation
- take part in tissue renewal
- be a component of hormones, enzymes, and antibodies
- act as a precursor for carnitine synthesis, which may help regulate fat metabolism, muscle function, and energy production
- participate in fat metabolism, specifically in the oxidation of long-chain fatty acids in mitochondria
- strengthen immune function
- increase growth hormone levels, making it useful for building muscle mass
- help prevent atherosclerotic plaque formation in arteries due to its affinity for lipoproteins
- boost collagen production as one of its components
- support mental focus and energy levels
- aid in zinc and iron absorption
Lysine and blood pressure
L-lysine may help lower blood pressure in people with hypertension.
Studies show that lysine supplementation in hypertensive individuals whose diets lack sufficient lysine can positively affect both systolic and diastolic blood pressure, lowering or normalizing it.
Lysine, stress hormones, and anxiety
Supplementing L-lysine in people with low dietary intake may help reduce chronic anxiety.
Additionally, combining lysine with arginine has been observed to normalize the hormonal stress response and lower cortisol, the primary stress hormone.
Lysine and cold sores
Lysine may help in combating cold sores – fluid-filled blisters around the mouth caused by the HSV-1 herpes virus.
HSV-1 can be triggered during periods of lowered immunity or chronic stress. Lysine may help prevent outbreaks and shorten their duration by hindering the virus’s replication and blocking access to arginine, another amino acid HSV-1 uses to replicate.
Lysine and calcium absorption
Lysine may increase calcium absorption from the digestive tract and improve bone mineralization.
By boosting calcium uptake in the intestines and reducing its excretion by the kidneys, lysine could be a valuable ally in preventing osteoporosis. Studies also suggest that taking calcium together with lysine leads to less calcium loss in urine compared to taking calcium alone. It is also believed that lysine may be an important regulator of calcium homeostasis in the body.
L-lysine requirements
For healthy adults, the recommended intake of L-lysine is estimated at 12–45 mg per kg of body weight per day, with 30 mg/kg/day as the average reference value.
Higher requirements may occur in malnourished individuals, those on plant-based or restrictive weight-loss diets, and in people with osteoporosis or HSV infections.
Since lysine is essential for growth, the need for it decreases with age. Recommended daily intakes by age are:
- Age 0–1 years – 64 mg/kg/day
- Age 1–4 years – 45 mg/kg/day
- Age 4–10 years – 35 mg/kg/day
- Age 10–14 years – 36 mg/kg/day
- Age 14–18 years – 34 mg/kg/day
- Age 18+ years – 30 mg/kg/day
Lysine deficiency in the human body
Vegetarians and vegans are most at risk of low lysine intake, as plant foods generally contain small amounts.
Common signs of lysine deficiency include:
- fatigue and weakness
- difficulty concentrating
- red eyes
- weakened immunity
- anemia
- cold sores
Most of these symptoms are nonspecific, making lysine deficiency hard to diagnose based on signs alone.
Lysine - how to use it? When to take it?
If dietary intake is too low, it is worth adjusting the meal plan to meet daily needs for this essential amino acid. When this is difficult or when demand increases, dietary supplements can be used.
Many lysine supplements are available on the market, in powder or tablet form. For best absorption, choose supplements containing free-form lysine.
There is no definitive recommendation for how long lysine supplementation should last, but current guidelines suggest not exceeding three months.
Lysine and vitamin C
It is beneficial to take lysine together with vitamin C, as both are important for proper body and immune function.
This combination may support antibody production, shorten infection duration, and help prevent illness. Together, lysine and vitamin C can strengthen the body and boost resistance to harmful pathogens.
Is lysine harmful? Side effects and contraindications for L-lysine use
Lysine is considered a safe dietary component, and overdose from food sources is unlikely. However, excessive supplementation (over 10–15 g/day) may cause nausea, vomiting, diarrhea, or abdominal pain. When taken as directed, no side effects have been reported.
Lysine should not be used by individuals with hyperlysinemia, a rare genetic disorder affecting lysine metabolism, as it may lead to elevated levels in the cerebrospinal fluid and blood. Such patients should limit lysine intake from food.
Caution is also advised for people with high blood calcium levels, as well as those with kidney or liver disease.