This amino acid is the most widely used NO booster around. That’s because in the body arginine is readily converted to NO with the help of the enzyme nitric oxide synthase. A recent study found that subjects taking arginine before a biceps workout experienced a 100% increase in biceps blood volume during the workout. Products that don’t use arginine typically use citrulline instead. Citrulline is converted in the body to arginine and may be absorbed more readily than arginine.
This flavonoid from the bark of the French maritime pine tree is a potent antioxidant. It increases NO levels from two opposite sides of the reaction. On the front end, Pycnogenol increases the activity of NOs to catalyze the conversion of more arginine into NO. On the back end, Pycnogenol quenches free radicals that can break down NO, resulting in higher NO levels for a longer period of time.
This derivative of the branched-chain amino acid (BCAA) valine has been shown to boost NO levels by more than 50% on its own. The main way that it works is by inhibiting the enzyme arginase, which normally breaks down arginine in the body. Inhibition of this enzyme results in maintaining higher arginine levels, which can lead to higher NO levels.
This table lists several NO boosters that contain either all three of the ingredients covered above, or at least two of them, for maximizing NO levels.