Adding L-Citrullin increases the plasma-L arginine in men

reference

Suzuki t, Morita M, Hayashi T, Kamimura A. The effects of a combined oral L-Citrullin and L arginine supplementation in healthy men on the plasma-L arginine level. Biosci Biotechnol Biochem . 2017; 81 (2): 372-375.

draft

double-blind, randomized, placebo-controlled study

participant

42 Healthy, non-weighted Japanese men aged 20-49; Smokers and men who took medication or nutritional supplements were excluded. The men were randomized in 1 of 4 groups:

1. placebo (corn starch) (n = 11)
2. l-citrullin alone 2.0 g/day (n = 11)
3. L-arginine alone 2.0 g/day (n = 10)
4. l-citrullin with L-arginine, each 1.0 g/day (n = 10)

Primary result measurement

Plasma level from L-Arginine after supplementation

important knowledge

One hour after supplementation, all groups showed an increase in L-arginine plasmaspiegel compared to placebo; However, the values ​​in the combination group L-Citrullin, L-arginine were significantly higher (placebo 5.4 ± 16.3; combination 121.9 ± 46.7; Citrullin alone 66.3 ± 33.6; arginine alone 72.3 ± 31.5). The values ​​in the combination group were about 40 % higher than in the group with L-arginine alone. None of the participants had side effects one of the treatments during the study.

practice implications

While previous animal studies have shown that the combination of L-arginine with L-Citrullin increases the L-arginine plasma levels, this is the first clinical study on humans to show this effect. L-arginine supplementation shows in men. Clinical studies in humans have shown that L-arginine supplementation can contribute to improving the erectile dysfunction (ED). ^{3 Insulin resistance, 4 and sporty performance. 5}

Specific for ED shows research that men with ED have low serum levels from L-Citrullin and L-arginine. ^{6 A reduced nitrogen oxide concentration is associated with an increased risk of erectile dysfunction. Arginine is a nitrogen oxide predecessor, so it makes sense that low concentrations of nitrogen oxide synthase substrates such as L-Arginine and L-Citrullin that could have a positive impact on ED.}

This is clinically significant in view of research, which shows the diverse and important health benefits of L-arginine supplementation in men.

There is also indications that complementary L-arginine can contribute to the prevention and treatment of cardiovascular diseases, which is probably due to its influence on the endothelial nitrogen oxide production. From 2016, the clinical benefits of L-arginine supplementation showed especially in ischemic heart disease and once again cited the synthesis of nitrogen oxide production as a key mechanism of the effect.

Due to previous in-vitro and in-vivo research, which show that L-Citrullin suppresses arginase activity, 10 The researchers of this present study speculate that this could be a possible mechanism that explains the significant increase with the combination of the 2 amino acids. Earlier investigations have shown that oral L-arginine has a reduced bioavailability, since arginase in the gastrointestinal tract (40 %) and in the liver (15 %) during the first round. By inhibiting arginase activity through the addition of L-citrulline, it is likely that more L-arginine can get through the intestine and the liver into the bloodstream. As was shown in this study and previous studies, L-Citrullin is a forerunner of L-arginine and can only increase the L-arginine level.

Since we know that L-arginine can have a positive impact on a man's health, it makes sense to examine this combination from a clinical point of view because it seems to improve the bioavailability of an oral L-arginine supplement. Since it was a small study, further investigations are required to further confirm this effect.