Even if you're perfectly healthy, or if you want to increase your health or athletic response, increasing your intake of Aminos through nutritional supplements is advised. L-Arginine was a popular Amino Acid supplement, for example, of bodybuilders and athletes well before it hit the mainstream consciousness. L-Arginine increases the body's production of human growth hormone (HGH), which is critical to increasing muscle mass. Additionally, N-acetylcysteine (NAC) boosts the body's production of antioxidants and antioxidants neutralize free radicals.