Since nitric-oxide booster/arginine supplements exploded onto the bodybuilding scene several years ago, scientists and bodybuilders alike have looked for synergistic compounds that can help increase arginine's effect on NO synthesis.
Since arginine is readily converted into NO in the body, supplements that either increase arginine conversion to NO or delay NO breakdown have served as the best candidates for synergistic benefits.
One study has found vitamin C combined with L-arginine increased nitric oxide levels greater than L-arginine alone. Vitamin C was reported to boost NO levels by neutralizing free radicals that can otherwise break down NO once it is produced. Since NO enhances blood flow to muscles (increasing the delivery of anabolic hormones and nutrients to muscles during and after exercise), and it enhances the muscle pump, keeping NO levels elevated will increase muscle size and strength over the long run.
In an attempt to measure the long-term effects of stacking L-arginine with vitamin C, scientists from Brazil conducted an eight-week supplementation study. Soccer players between the ages of 17 and 19 were given 3 grams of L-arginine along with 1 g of vitamin C, or subjects were given 1 g of vitamin C only. All study subjects performed a standard weight-training program in which they lifted three times per week for the duration of the experiment. This research marked the first time that L-arginine and vitamin C had been studied together in trained athletes.
After eight weeks, the arginine/vitamin C group had experienced significant improvements in lean body mass as well as muscular strength, as measured by the maximum weight they could lift on the leg extension with both the right and left leg. Additionally, the combo group experienced a significant decrease in bodyfat percentage, despite the fact that the athletes were already well trained and relatively lean to begin with. In contrast, the group that only received vitamin C experienced no significant changes in any of the above measures.
This means that larger individuals or anyone looking to maximize NO production should supplement with 3-5 g of arginine when they take it. Although the most critical time to take arginine and vitamin C is 30-60 minutes before exercise, you can also take a dose 30-60 minutes before bed. Make sure to take 1,000 milligrams of vitamin C with each arginine dosage to help prevent NO breakdown and magnify the results.
Reference: A. Gerseli et al., "The effects of oral L-arginine supplementation on muscular strength in young soccer players," Journal of Sports Science and Medicine, Supp. 10:35, 2007.