Doctor's Best Sustained Plus Immediate Release L-Arginine, Non-GMO, Vegan, Gluten and Soy Free, 500 mg, 120 Count

Sustained plus Immediate Release L-Arginine contains this conditionally essential amino acid in a bilayer tablet, with two tablets providing 500 mg of sustained release and 500 mg of immediate release L-arginine in a formula that allows for enhanced blood levels of this nutrient. Most supplemental L-arginine is quickly absorbed into circulation and is extremely efficiently metabolized, yielding only a short-lived boost to L-arginine levels. Sustained plus Immediate Release L-Arginine tablets are specifically manufactured to immediately increase blood levels of L-arginine and then to sustain this beneficial increase continuously over an 8-hour period.*

L-arginine has been shown to support the cardio- vascular system, promote vigorous heart function and enhance healthy circulation throughout the body through its conversion to nitric oxide.* Research suggests L-arginine supplementation may also have positive benefits on athletic performance.*

Benefits:

Promotes a Healthy Cardiovascular System, Enhances Healthy Circulation and Supports Heart Function.*

The normal aging process in humans has been found to be associated with progressive changes in endothelial function (cells that line the inner surfaces of blood vessels). Research suggests that a major reason for these common changes associated with aging is reduced production or bioavailability of nitric oxide (NO) in vessels and tissues2. L-arginine is a substrate for the enzyme nitric oxide synthase, required for the production of nitric oxide in the body. Nitric oxide is a substance critical for the maintenance of normal vascular function3. NO mediates a number of physiological effects on the cardiovascular system, including supporting healthy endothelial function, enhancing cardiovascular health and displaying potent antioxidant properties against free radical species.

Oral L-arginine supplementation has been shown in clinical studies to support various aspects of cardiovascular health. A randomized double-blind placebo-controlled trial found that six weeks of L-arginine supplementation enhanced circulation, improved arterial compliance and supported healthy heart function compared to placebo. The mechanism of L-arginines effect was due to its role in No production. Other clinical trials have shown that oral L-arginine supplementation contributes to enhanced exercise tolerance because of its ability to enhance cardiac circulation and vasodilation of blood vessels1. Multiple clinical trials have been conducted in which L-arginine at various doses has been administered to healthy individuals to assess its impact on cardiovascular function and health. In one such study, L-arginine enrichment of the diet in healthy individuals was shown to cause a reduction in arterial blood pressure, while other studies in healthy individuals did not report this effect. However, the overall results of these and other clinical trials showed that long-term administration of this amino acid significantly enhanced endothelial function4.

In a small, double-blind, randomized controlled crossover trial, twelve healthy older-aged adults (over 70 years of age) took supplemental L-arginine or placebo for 14 days, and treatments were then crossed over after a 14-day washout period. Flow-mediated dilation (a measure of endothelial function) of the brachial artery was monitored by ultrasound. L-arginine improved flow-mediated dilation by an average of 5.7% whereas placebo had no effect. Since endothelial function is normally compromised in healthy adults as we age, the results indicate that L-arginine is a useful supplemental nutrient to promote healthy endothelial function in healthy, aging individuals2. However, it is clear from other research that the benefits associated with L-arginine supplementation are not limited to older adults.

An interesting study was conducted in which young healthy men consumed an L-arginine-enriched diet for ten days. Measures of endothelial function (as flow-mediated vasodilation of the brachial artery), total cholesterol, HDL and LDL cholesterol, triglycerides, LDL size, Lipoprotein (a) and reduced glutathione concentrations were taken at baseline and at 2, 4, and 6 hours after consumption of a standardized oral fat load. The dietary fat decreased flow-mediated vasodilation significantly at 2 and 4 hours, and returned to baseline levels by 6 hours. The individuals were then instructed to consume the arginine-enriched diet for 10 days. On day 11, the same tests were repeated. The results of the study revealed that supplementation with L-arginine for ten days significantly corrected the drop in flow-mediated vasodilation noted after consumption of a standardized fat load. Essentially, L-arginine supplementation was found to enhance endothelial function in young, healthy men5.

Animal studies suggest further benefits of supplemental arginine on parameters of cardiovascular and endothelial function. Studies in rabbits have shown that oral supplementation of L-arginine in both normocholesterolemic (those with normal levels of cholesterol) and hypercholesterolemic animals (those with high cholesterol) was protective against endothelial damage caused by exposure of the animals to tobacco smoke. Other studies have shown additional benefits of L-arginine. For example, a study was conducted in which rabbits were fed a high-cholesterol diet and then supplemented with L-arginine for 10 days. Compared to control animals (who did not receive L-arginine), those in the L-arginine group had significant improvements in endothelial function and vasodilation4.

The Benefits of Sustained Release combined with Immediate Release Arginine.

L-arginine undoubtedly has many benefits for cardiovascular health. Studies show that arginine is metabolized extremely efficiently by the body and used as a precursor for nitric oxide formation. L-arginine reaches its highest concentration in the bloodstream within an hour of its use and then tends to taper off quickly6. For this reason, relatively large doses of this amino acid taken frequently throughout the day are required to produce positive results. Blood levels of arginine are quickly depleted and frequent replenishment is necessary to ensure its availability.

Recent technological advancements have allowed for the development of sustained release forms of this beneficial amino acid. Sustained plus Immediate Release L-Arginine contains the amino acid L-arginine in the form of arginine alpha-keto-glutarate. The bilayer tablet design allows for the benefits of immediate arginine uptake, resulting in a quick spike in arginine concentration, along with the longer-term effects of sustained arginine blood levels through sustained release of this important amino acid. This allows for higher arginine blood levels for a continuous period of up to 8 hours. With increased and consistent blood levels, less L-arginine is required, the frequency of dosing necessary to maintain its benefits is reduced and the efficacy is maintained over a longer period of time all tangible benefits worth looking for in a quality L-arginine supplement.

* This statement has nt been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Scientific References:

1. Appleton, J. 2002. Alternative Medicine Review 7: 512-522.

2. Bode-Boger, S. M., Muke, J., Surdacki, A., Brabant, G., Boger, R. H. and Frolich, J. C. 2003. Vasc Med 8: 77-81.

3. Brown, A. A. and Hu, F. B. 2001. Am J Clin Nutr 73: 673-86.

4. Cylwik, D., Mogielnicki, A. and Buczko, W. 2005. Pharmacol Rep 57: 14-22.

5. Marchesi, S., Lupattelli, G., Siepi, D., Roscini, A. R., Vaudo, G., Sinzinger, H. and Mannarino, E. 2001. J Clin Pharm Ther 26: 343-9.

6. Miller, A. L. 2006. Altern Med Rev 11: 23-9.