Nutricost combines two of the body's most important building blocks into one easy-to-take supplement. The amino acid's: L-Arginine and L-Ornithine. L-arginine and L-ornithine, or simply arginine and ornithine, are two amino acids that share a lot in common in spite of one significant difference. Your body relies on both arginine and ornithine amino acids to function properly, and they work together, and separately.