L-lysine is an essential amino acid and therefore must be supplied in the diet. L-lysine's popularity as a supplement began as some studies found it to have antiviral action against herpes simplex virus..
The following foods have the highest concentration of L-lysine.
- Rich Sources: meat and poultry, milk
- Other Sources: cheese, eggs, fish, lima beans, potatoes, soy products, yeast
- Proteins found in grains are typically low in L-lysine; small amounts are found in vegetables and fermented foods.
The following are the primary uses for L-lysine: 
- Herpes Simplex Virus: Several clinical studies show that L-lysine is beneficial in preventing and shortening outbreaks of herpes simplex infections.
- Osteoporosis: One study has shown that L-lysine increases intestinal absorption and improves renal conservation of calcium thus it has been considered in the treatment of osteoporosis. More research is needed in this area.
- L-lysine is available in capsule, powder, and tablet form.
- No RDA has been established for L-Lysine. To determine what your specific requirements are talk to your naturopathic doctor or other trained medical professional.
- General Adverse Effects: High doses (>10-15g/day) may cause gastrointestinal symptoms such as nausea, abdominal cramps, and diarrhea.
- Pregnancy Breastfeeding: One should only consider using supplemental L-lysine at this time if the diet is low in this amino acid.
- Contraindications: L-lysine supplementation is contraindicated in those with the rare genetic disorder hyperlysinemia/hyperlysinuria.
- Precautions: Proteins high in L-lysine relative to L-arginine such as casein are associated with elevated cholesterol. Therefore, individuals with hypercholesterolemia should be cautious of this if interested in supplementing with L-lysine. Those with hepatic and renal failure should also exercise caution if using supplemental L-lysine.
- Drug Interactions: None are expected.
- Hendler Sheldon S, Rorvik David (Editors) (2008) PDR for Nutritional Supplements, Medical Economics Company Inc.
- Griffith Winter H (2000) Vitamins, Herbs, Minerals & Supplements: The Complete Guide MJF Books.