Question: I read that L-lysine should be taken on an empty stomach.
Answer: L-lysine appears to reduce the severity and frequency of herpes simplex viral infections which are also known as cold sores or fever blisters. Lysine can be used orally or topically for herpes simplex; it doesn't need to go through the brain to help cold sores.
The reasons you would want to take L-lysine on an empty stomach is so your body can absorb a large amount of the amino acid and probably also because another amino acid called arginine will interfere with L-lysine's affect on the herpes simplex virus. Foods like legumes, whole grains and nuts contain arginine. If you take L-lysine on an empty stomach, then you won't be ingesting any arginine at the same time.
Sources:
Elish D, Singh F, Weinberg JM. "Therapeutic options for herpes labialis: experimental and natural therapies." Cutis. 2005 Jul;76(1):38-40.
Algert SJ, Stubblefield NE, Grasse BJ, Shragg GP, Connor JD. "Assessment of dietary intake of lysine and arginine in patients with herpes simplex." J Am Diet Assoc. 1987 Nov;87(11):1560-1.
