Nitric oxide supplements are the hottest thing on the market. Athletes are buying them in droves without knowing exactly what is happening in the body. Supplement companies claim to educate their consumers with pamphlets and informational websites, but these only offer an incomplete story of what is actually happening. Manufacturers state that nitric oxide supplements, via the compound arginine alpha-ketoglutarate, gives the athlete added energy,
mental focus, workout intensity, perpetual pump and muscle growth. Upon closer investigation, these effects are largely exaggerated and in some cases completely fallacious. While arginine is involved in the regulation of growth hormone release, the supplemental dosages that would stimulate a noticeable effect are astronomical. Arginine is also a substrate for nitric oxide; an effect that is enhanced when combined with alpha-ketoglutarate. Nitric oxide is released by the walls of the blood vessels that cause a decrease in the resistance and an increase in blood flow to the skeletal muscles. Arginine may also stimulate the release of epinephrine from the adrenal gland. These two effects are mostly beneficial to endurance athletes, not strength athletes like the manufacturers suggest. Grasemann et al. (2005) determined that participants receiving as little as 200 mg of L-arginine showed a significant increase in nitric oxide formation, as well as significant increases in plasma L-arginine and sputum L-arginine. This indicates that L-arginine supplementation does indeed induce nitric oxide formation. Rytlewski et al. (2005) found that three weeks of L-arginine supplementation lead to significant drops in systolic blood pressure, diastolic blood pressure, and mean arteriole pressure while elevating urinary excretion of NOx (nitrates) and mean plasma levels of l-citrulline. However, plasma L-arginine levels were not effected even with 300 mg of supplementation. Thusfar it has been established that L-arginine supplementation does indeed stimulate nitric oxide synthesis. Now it must be addressed whether or not this is beneficial to athletes.
Paddon-Jones et al. (2004) found that nitric oxide supplementation does not provide an ergogenic effect to healthy individuals. Miguez et al. (2004) found that 4 weeks of L-arginine supplementation increased serum triglyceride levels and significantly increased levels of low-density lipoprotein (LD) cholesterol. This is obviously cause for concern and needs to be further investigated. Evans et al. (2004) sought to find the optimal dosage of L-arginine to elicit the greatest effect on nitric oxide synthesis. Manufacturers recommend upwards of 6000-10000 mg/day but many athletes report taking even higher dosages as much as 35000 mg/day, nearly six times the recommended intake. Evans (2004) found that half the participants supplementing with 20000 mg/day reported serious adverse side effects from L-arginine supplementation and over half of the participants reported severe side effects when taking more than 20000 mg/day. A significant portion of individuals supplementing with 9000 mg/day reported adverse effects, and over the duration of the supplementation period, no participants experienced any sort of weight gain. Chu et al. (2004) found that L-arginine supplementation impaired pulmonary endothelium-dependent relaxation of vascular tissue. This may lead to potentially dangerous vascular spasms and cardiovascular abnormalities.
It has been found that L-arginine keto-gluterate supplementation stimulates rapid vasidilation in a non-discriminatory fashion. Significant vasodilatation causes a drop in blood pressure (because as the veins widen, the pressure drops). Baroreceptors in the aortic arch and in the carotid sinus will detect this fast, significant drop in both systolic and diastolic blood pressure. During exercise, it is imperative that diastolic blood pressure remain constant. It is natural for systolic blood pressure to rise during the onset of exercise, but diastolic blood pressure values must remain constant. A drop in either during exercise is cause for great concern and can lead to serious cardiovascular damage. In order to protect the body from going into shock, vasomotor centers in the medulla will cause the blood vessels leading to the brain to constrict in order to increase blood pressure going into the brain (too much blood can severely damage the brain, just like too little). This is a dangerous sequence that can potentially lead to a vascular catastrophe.
Based on the available research, this author strongly recommends that athletes avoid nitric oxide and hemodilator supplements in the interest of safety. Moreover, it has been suggested that these supplements have little or no anabolic or ergogenic benefits for the athlete.
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