Plant-based athletes are more likely to be in a dietary lysine shortfall, as plant proteins tend to be lower in lysine relative to animal proteins (legumes excepted). Athletes with high connective tissue demands (runners, martial artists, gymnasts) may benefit from ensuring adequate lysine for collagen maintenance. Athletes prone to illness during heavy training blocks may find lysine's immune role relevant.

L-Lysine for Athletes: Performance Evidence

L-lysine is an essential amino acid — one that the body cannot synthesise and must obtain through diet or supplementation. It is best known in popular culture as a supplement for managing cold sores, but for athletes the relevant science covers collagen synthesis, carnitine production, and immune function.

Mechanism in Sport

L-lysine contributes to athletic performance through several interconnected pathways:

Collagen synthesis. Lysine is required alongside proline for the hydroxylation steps that stabilise collagen fibrils. Tendons, ligaments, bone matrix, and cartilage all depend on collagen for structural integrity. Athletes who train heavily place high mechanical loads on connective tissue, and lysine availability may be a limiting factor for collagen repair (Shaw et al., 2017).

Carnitine biosynthesis. The body synthesises carnitine from lysine and methionine. Carnitine facilitates the transport of long-chain fatty acids into mitochondria for beta-oxidation. This pathway is especially relevant for endurance athletes, for whom fat oxidation contributes meaningfully to energy supply during prolonged exercise.

Immune support. Intense training temporarily suppresses immune function. Lysine has an established role in immune cell function and is a well-studied inhibitor of arginine-dependent viral replication (herpes simplex, for example). The immune-supportive role is an indirect performance benefit: staying healthy allows more consistent training.

Calcium absorption. Animal studies have indicated that lysine may enhance intestinal calcium absorption and reduce urinary calcium excretion. While human data on this pathway are limited, bone health is relevant for athletes in high-impact sports.

Strength and Endurance Evidence

Direct evidence for L-lysine supplementation improving strength or endurance performance in isolation is modest. Most of the relevant human studies examine it as part of protein intake (where lysine is a constituent amino acid), not as an isolated supplement:

As part of complete protein, lysine contributes to the leucine-independent stimulation of muscle protein synthesis via mTOR-independent pathways.
Its role in carnitine synthesis links it indirectly to fat metabolism during endurance activity, but direct lysine-supplementation trials measuring endurance output are scarce.

The honest picture is that lysine deficiency impairs performance-related physiology; adequate intake supports it. Supplementation above dietary adequacy is less clearly beneficial in well-nourished athletes.

Effective Protocol

For most athletes, dietary protein (meat, fish, dairy, legumes) provides adequate lysine. Supplementation may be considered when:

Dietary protein is restricted (plant-only diets that are low in legumes).
Training volume is very high and connective tissue recovery is a concern.
Recurrent upper respiratory infections suggest immune depletion.

Products such as NOW L-Lysine 1000mg 100tabs and OstroVit Lysine 200g provide standardised supplemental doses. OstroVit AOL 3000 120caps combines arginine, ornithine, and lysine in a single formula.

Who Benefits?

Plant-based athletes are more likely to be in a dietary lysine shortfall, as plant proteins tend to be lower in lysine relative to animal proteins (legumes excepted).
Athletes with high connective tissue demands (runners, martial artists, gymnasts) may benefit from ensuring adequate lysine for collagen maintenance.
Athletes prone to illness during heavy training blocks may find lysine's immune role relevant.

Honest Verdict

L-lysine is not a performance enhancer in the dramatic sense. It is an essential amino acid that, when adequate in the diet, supports collagen integrity, carnitine synthesis, and immune function — all of which are relevant to sustained athletic performance. Deficiency is worth correcting; supplementation in an already well-nourished athlete produces smaller and less certain returns. Prioritise complete dietary protein first.

FAQ

Is L-lysine useful for muscle building?

Lysine contributes to protein synthesis as an essential amino acid, but it does not selectively drive muscle growth above what a complete protein diet provides. For muscle building, total protein intake and leucine content are the primary levers.

How much L-lysine do athletes need?

Athletes consuming adequate dietary protein from varied sources typically meet lysine needs without supplementation. Plant-based athletes relying on low-legume diets are the most likely to benefit from supplemental lysine.

Can I take L-lysine with other amino acids?

Yes. L-lysine is compatible with other amino acid supplements. Combination formulas exist (such as products combining lysine, ornithine, and arginine), and lysine is a component of complete protein supplements.

References

Shaw, G., Lee-Barthel, A., Ross, M. L., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. American Journal of Clinical Nutrition, 105(1), 136–143. https://pubmed.ncbi.nlm.nih.gov/27852613/

Demarquoy, J., & Le Borgne, F. (2015). Crosstalk between mitochondria and peroxisomes. World Journal of Biological Chemistry, 6(4), 301–309. https://pubmed.ncbi.nlm.nih.gov/26629313/