Citrulline Treats Erectile Dysfunction, Fights Aging and Obesity


Citrulline treats erectile dysfunction and increases virility. It also functions as a potent ergogenic aid during exercise.

Citrulline is a cheap, safe, over-the-counter, amino acid.

Citrulline treats erectile dysfunction

Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction.

In this study, 24 men, average age 56, with mild erectile dysfunction, took either 1.5 grams of citrulline, an amino acid, or placebo, for one month. As it was a cross-over study, all the men took part in both placebo and citrulline segments. In the treatment arm, 50% of the men reported an improvement in erectile function, compared to 8% of the men in the placebo arm. Frequency of intercourse rose from 1.3 per month at baseline to 2.3 at the end of the treatment phase. The authors conclude:

Although less effective than phosphodiesterase type-5 enzyme inhibitors [such as Viagra], at least in the short term, L-citrulline supplementation has been proved to be safe and psychologically well accepted by patients. Its role as an alternative treatment for mild to moderate ED, particularly in patients with a psychologically fear of phosphodiesterase type-5 enzyme inhibitors, deserves further research.

Citrulline appears safe. It works by increasing levels of arginine, which it does more efficiently than does arginine supplementation itself, and this in turn increases levels of nitric oxide, which is the principal factor increasing penile blood circulation. Arginine is a potential exercise ergogenic, with some research suggesting that it increases levels of growth hormone, so it seems that citrulline may do the same.

Citrulline increases exercise capacity

A study done on mice found that citrulline increased exercise time to exhaustion.

Much more impressively, in humans, the ingestion of citrulline resulted in greatly decreased sensations of fatigue, and a 34% increase in the production of aerobic energy through ATP.

Also, in a study in which 41 men were the subjects, citrulline dramatically increased the number of reps the men could do on the last set, and also substantially decreased post-exercise muscle soreness.

L-citrulline decreases mortality and fat mass, increases muscle mass, in rats

A recent study found that Citrulline Supplementation Induces Changes in Body Composition and Limits Age-Related Metabolic Changes in Healthy Male Rats. Aged male rats were supplemented with citrulline at 0.1% of their diet (1 gram per kg food). Over a 12-week period, the supplemented rats had zero mortality, compared to a death rate of 20% of the controls. They also had 9% greater lean mass, 13% lower fat mass, and oxidative stress was much lower.

There appears to be no reason that this writer can see why these results wouldn’t apply equally well to humans. At 0.1% of the diet as citrulline, one 750 mg capsule a day might just do it, which isn’t much to change body comp for the better. Note that these were already healthy animals, so the citrulline was not correcting some defect; therefore it could increase lean mass even if you’re already doing everything right.

The question I have from this study is whether citrulline’s effects on erectile function work acutely, that is, after one dose, or does it need to be taken continually. My guess here is that it would indeed work acutely. Indeed, in exercise studies such as the above cited one, citrulline worked immediately after ingestion, which suggests that for both purposes (erectile dysfunction and ergogenic enhancement), daily doses are unnecessary, the supplement needing only to be taken immediately before the desired effect, whether exercise or sex.
L-citrulline is available at Amazon.

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  1. David says:

    Regarding timing – when is the best time to take this supplement? Anabolic/Catabolic? Fasted/Unfasted?

    • P. D. Mangan says:

      David, I’m thinking maybe fed/anabolic is better. Amino acids have the potential to shut down autophagy, although leucine is the main signalling amino acid in that situation, and citrulline may do nothing in that regard. So if one wanted to be on the ultra-safe side, fed/anabolic.

  2. pzo says:

    I’ve been taking L-Citrulline sporadically for about a half year. It’s really inexpensive if you buy the Bulk Supplements brand. I throw it in scrambled eggs, protein drinks, or just in water. I can’t say if it has helped my, um, performance or not, it just seems like the results are lab proven w/o caveats, so why not?

    The obvious unanswered question is, “Is this linearly dose dependent?” One and a half grams a day is almost nothing. How about a teaspoon or tablespoon? That’s 3 or 9 grams respectively per the info on my Bulk Supplements bag.

    Sex 2.3 times per month? How sad!

    • pzo says:

      Further, rereading this article, it would appear that the amount needed for the life extension benefits are in the multi-grams per day range. I presume the rats were being fed some kind of dry chow, most of the foods we eat are not dry, so I’m not sure how to convert the 1 gram per kg of food to human intake. `

      I’ll make a stab at it here, no guarantees on my math. Taking a look at a box of scalloped potatoes, the net weight is 5.25 ounces and it requires the additions 2.75 cups of water and milk which would weigh 1 3/8 pound. So the dry weight multiplies out to 4.2. The box, prepared has 500 calories, including 2 tablespoons of butter. For the mythological 2000 calories a day standard, that’s four boxes a day, or 21 ounces of dry food, which is .6 kg. At the rat’s .1%, that’s only 6 mg a day of L-Citrulline.

      I’m guessing I failed in my math……………

  3. paul says:

    Thanks for the useful article! I’ve just been reading your supplements book and I”ve been looking at this supplement though it seems to be mostly sold as Citrulline Malate at least in the UK. I’m not sure if there’s any real differences in the possible effects, with the additional Malate? Guess it shouldn’t make too much of a difference, no idea really.

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