Lysine is an essential amino acid which promotes collagen growth, supports the immune system, and helps the body absorb zinc, calcium, and iron. Those with lysine deficiency may experience nausea, red eyes, hair loss, poor concentration, irritability, anemia, and reproductive system concerns.
Lysine is found in foods like chicken, red meat, eggs, fish, beans, spirulina, cottage cheese, and wheat germ. Some people take lysine supplements and when not exceeding a daily dose of 3 grams rarely results in side effects. However, those who take 10 to 15 grams a day may experience diarrhea, stomach cramps, and nausea.