Health, Myths, Fraud and the Crisis

Posts tagged ‘Nitric oxide’

Efficacy of oral supplementation of L-arginine to enhance Nitric oxide synthesis

L-arginine is widely touted and promoted as a supplement for enhancing blood flow and nutrient delivery. So I got curious whether its just about money or true. That is what I found :

Our body converts L-arginine into Nitric oxide (NO).  NO is a ubiquitous mediator that is formed by a family of enzymes named NO synthases. In the brain, NO acts as a neurotransmitter; in the immune system NO acts as a mediator of host defense; and in the cardiovascular system, NO mediates the protective effects of the intact  endothelium (inhibits adhesion of blood platelets), acting as a vasodilator.

Scientific studies have shown that NO significantly reduces blood pressure levels. NO also enhances health in a number of other ways. It improves immune function, stimulates the release of human growth hormone (HGH), promotes healthy sexual function (since it stimulates production of an enzyme that leads to smooth muscle relaxation of the arteries), may boost energy levels, helps to build muscle, and may reduces adipose tissue body fat. However most studies I could find do not support the claims of the supplement industry regarding oral supplementation of L-arginine.

Arginine is the precursor for nitric oxide leading to the supposition that oral supplementation can serve as a potent nitric oxide stimulator. This position is also based on the findings that significant increases of blood serum arginine levels induce significant levels of vasodilation in healthy persons when fasting (12).

However, such blood levels of arginine require direct infusion as high oral doses generally are not tolerated. In fact, oral dosages as low as 10 grams per day have been associated with significant gastric distress (16).

A substantial body of research dating back to the 1990’s, demonstrates that oral feeding of arginine is ineffective for increasing nitric oxide production, as compared to intravenous infusion, which is largely impractical.

Studies:

Efficacy and safety of oral l-arginine in acute myocardial infarction CONCLUSIONS: This study, which is the first attempt to use L-arginine in MI, showed that oral L-arginine supplementation was well tolerated. Beneficial nonsignificant trend was observed towards reduction of major clinical events.

CONCLUSIONS: Endothelial dysfunction was apparent in patients with heart failure despite rigorous vasoactive treatment. Oral administration with l-arginine was ineffective in influencing endothelial function in these patients.

Conclusions— In patients with PAD (peripheral arterial disease), long-term administration of L-arginine does not increase nitric oxide synthesis or improve vascular reactivity. Furthermore, the expected placebo effect observed in studies of functional capacity was attenuated in the L-arginine-treated group. As opposed to its short-term administration, long-term administration of L-arginine is not useful in patients with intermittent claudication and PAD.

Abstract: … Nonetheless, intravenous or dietary (oral) administration of relatively large doses of L-arginine has been shown to result in enhanced NO formation in subjects with impaired endothelial function at baseline. In several controlled clinical trials, long-term administration of L-arginine has been shown to improve the symptoms of cardiovascular disease. However, in other trials L-arginine was not beneficial, and in a recent study, the authors reported higher mortality of subjects receiving L-arginine than those receiving placebo.

 

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