Boost Your NO Booster
Loyal readers are well versed in the importance of nitric oxide for building muscle and improving recovery. NO helps to dilate blood vessels so more blood can flow to working muscles during exercise. This is important for delivering nutrients, such as glucose, that help produce energy, and amino acids to help stimulate protein synthesis — resulting in more muscle gained.
Nitric oxide also allows for an increased delivery of anabolic hormones such as testosterone, growth hormone and insulinlike growth factor-I, which are key for packing on more muscle. In addition, testosterone helps to immediately boost strength by increasing the force of muscle contractions.
Now, here's a trick to make your NO even more powerful: before your workouts, boost your nitric oxide levels by stacking arginine with citrulline supplements. Since citrulline is readily converted to arginine in the body, this synergistic combination helps bump up NO more than either supplement alone. New research is now confirming what we've been recommending all along, and the results are even more impressive for citrulline than originally expected.
Although citrulline is a byproduct of arginine conversion to NO, it can be converted back to arginine through a two-step process. By elevating arginine levels, citrulline indirectly helps to increase NO synthesis. As a bonus, citrulline plays an important part in delaying exercise fatigue through its role in liver detoxification. During all-out exercise such as heavy lifting, ammonium levels build up within the muscle and the blood, which can lead to muscle fatigue. Citrulline helps the body to convert ammonium into urea as part of the urea cycle. Citrulline malate supplements have been shown to increase energy stores in the form of adenosine triphosphate by approximately 35%, while also increasing creatine phosphate levels by 20%.
The Study
In order to directly compare the arginine-boosting abilities of supplemental citrulline and arginine, researchers from University Medical Centre Hamburg-Eppendorf (Germany) conducted research in which subjects received a different supplement every week for six weeks (1.5 grams of citrulline, 3 g of citrulline, 6 g of citrulline, 3 g of rapid-release arginine, 3.2 g of time-released arginine, and a placebo, each taken in two divided doses daily). On the seventh day of every supplementation period, subjects were given half the daily dosage and then had blood levels of arginine recorded along with several measures of NO production. Each week of supplementation was followed by a one-week washout period in which no supplements were given.
The Results
All the supplements (except for the placebo) raised arginine levels, but the citrulline supplements surprisingly resulted in equal or greater increases than the arginine supplements. The highest dosage of citrulline (3 g twice per day) was also the most effective supplement for increasing NO synthesis. The researchers believe that citrulline may be more effective than arginine for boosting arginine levels and NO synthesis because a good portion of the supplemental arginine gets used up in the digestive system before it reaches the bloodstream, which doesn't happen with supplemental citrulline.
Dosage
For maximal NO-boosting effects, take 3-5 g of arginine along with 1.5-3 g of citrulline 30-60 minutes before your workouts. A second dosage can be taken immediately following the workout to boost delivery of critical nutrients needed for recovery and muscle growth. Also consider taking a dose of arginine first thing in the morning before breakfast and about one hour before your bedtime meal.
