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L-Citrulline – Better than L-Arginine? – 10 minutes read

What is to know about L-citrulline?

L-citrulline is actually a non-essential amino acid. L-citrulline is a naturally occurring amino acid in food such as watermelon. Our kidneys change citrulline into arginine and nitric oxide. Well, this one you heard before. They are important for our heart (our engine) and the health of our blood vessel (our highway).

In short, some of L-citrulline will be converted to arginine and boost the production of nitric oxide and nitric oxide helps our arteries to relax (smooth muscle cells in blood vessel) resulting oxygen rich blood circulating through arteries and work better in terms of improving blood flow throughout our body, we called it vasodilation. Why don’t we take L-arginine you ask? Well, interestingly, consuming citrulline may increase arginine in the body more than consuming arginine itself, we will discuss about this further. Other than that, it is also associate with lower blood pressure. Imagine there is no traffic jam in highway, Smooth! Besides, people also take L-citrulline for improving athletic performance. Citrulline has important roles in our body, but unlike for other amino acids, it is not used to build proteins. Although it is not directly use to build proteins, it has been shown to increase protein synthesis by stimulating signalling pathway involved in muscle building. That’s why you can see citrulline in various muscle building supplement range especially for pre-workout supplements. Furthermore, it plays a necessary part in urea cycle, especially removing ammonia from our body as it increases plasma level of ornithine and arginine and improve ammonia recycling process and nitric oxide metabolisms. In addition, citrulline may reduce the liver’s uptake of certain amino acids and prevent their breakdown.

There is evidence show that L-citrulline supplement may help to lower blood pressure in people with elevated blood pressure. Elevated blood pressure increases the risk for high blood pressure and heart disease.

L-arginine or L-citrulline better?

Let’s dive down a little bit. Oral L-arginine undergo significant breakdown occurs by enzyme arginase in our gastrointestinal pathway that hydrolyses arginine into ornithine and urea. This result in low plasma L-arginine levels and reduced bioavailability of L-arginine as a substrate for endothelial nitric oxide synthesis (eNOS). L-citrulline itself is a precursor arginine, either natural or synthetic citrulline can be converted into arginine effectively in the urea cycle. Unlike L-arginine, dietary L-citrulline is not broken down by arginase and bypasses liver uptake and degradation. It has been shown that L-citrulline is an inhibitor of arginase. Therefore, it can be said that L-citrulline is a more efficient intervention for increasing L-arginine bioavailability and nitric oxide production than oral L-arginine.

Benefits of L-citrulline

1. Cardiovascular Health (Heart and Blood Vessel)

Studies have shown L-citrulline is able to improve the ability of blood vessel to widen and potentially improve for blood pressure and blood flow to tissue especially for people who are having heart disease or hypertension. There is correlation between the increase of plasma arginine and serum nitric oxide with L-citrulline supplementation with the improvement of atherosclerosis marker. Our blood pressure would be more stable with more relax blood vessels.

2. Exercise Performances

Due to its ability to enhance blood flow, studies have shown that it can increase the oxygen content in muscle tissue and improve oxygen usage in the exercising muscle and allow for better exercise performance especially endurance exercise. Whereas for weight training, it can help participants to perform more repetitions compared to placebo and lower the intensity of Delay Onset Muscle Soreness (DOMS). Other than that, it could help to decrease fatigue and increase lower body weight training performance.

3. Erectile Dysfunction (ED)

The same effect on blood vessel also helps improve symptoms of erectile dysfunction (ED). L-citrulline enhance eNOS and increase nitric oxide that increases blood flow to man’s genital. Studies show the increase in blood flow appeared to decrease mild ED symptoms and improve the ability to maintain an erection. However, it does not work as well as ED drugs such as Viagra, but it would be a safe option. We should note that there haven’t been any studies on the use of L-citrulline for severe cases of ED. Therefore, if you are having severe ED, it’s best to consult with your doctors.

Source of L-citrulline

We can find L-citrulline in some of the food groups namely fruits especially watermelon, legumes, meat and nuts. But most people use supplements to increase the amount of citrulline in their diets. All in all, L-citrulline supplements are available over the counter and seems to be safe with studies even go up to 15g and without any reported side effect. However, higher doses did not appear to increase serum arginine which means there is a limit of how much of a supplement our body can use, just like everything else, more is not better. This supplement may promote healthier blood vessels and lower blood pressure, especially in people with heart conditions or high blood pressure. Nonetheless, we would still encourage intake from dietary food source however it wouldn’t hurt to take L-citrulline supplements for extra benefits.

The Next Best Thing: L-citrulline + L-glutathione

Still remember, we discussed about L-glutathione being the antioxidant and detoxification greatness, how does it work synergistically with L-citrulline as a blood circulation enhancer? Having L-citrulline to increase Nitric Oxide to enhance blood circulation, we are yet to overcome to maximum potential of Nitric Oxide as it breaks down easily in our blood stream. So, L-glutathione works to maximize the potential of nitric oxide by preventing it from breakdown. Well, let us give you a rough idea. L-citrulline increase the production of nitric oxide, and with the presence of glutathione as an antioxidant, the nitric oxide is protected by glutathione from oxidation.

It has been shown that glutathione and nitric oxide activity are linked as some cells are unable to synthesize nitric oxide in the absence of glutathione. Recent research suggests that L-glutathione would also potentiate nitric oxide synthesis.

L-citrulline + L-glutathione showed an improvement in cGMP activity (relax vascular smooth muscle cells lead to vasodilation), plasma nitric oxide metabolites, nitrite and nitrate. Nitrate and nitrite are also substrates for nitric oxide synthesis, that suggest would likely play a role in muscle protein synthesis and muscle performance when combine with resistance training. There are studies shown that combination of citrulline and glutathione increase muscle strength that significantly correlated to increase in lean mass. Therefore, you may give it a try if you wish to give it extra boost for your blood circulation and exercise performances.

It is always great to equip ourselves with a basic knowledge of nuts and bolts of Nitric Oxide Synthesis, we can at least be better consumers, paying attention to ingredients and amounts when evaluating a product.