Should you believe claims that nitric oxide supplements will enlarge muscles and increase endurance? Actually, there are no products that contain nitric oxide because it is too unstable. However, supplements containing arginine (an amino acid) in combination with another blood vessel widener, alpha- ketoglutarate, can stimulate the blood vessels to increase production of nitric oxide. This dilates blood vessels that bring blood to muscles. Several studies show that the nitric oxide releasers may help athletes exercise longer, but the data are weak, sparse and not very impressive. If you take these supplements and do not exercise to your maximum, you are wasting your money. However, if you are already exercising as hard and as fast as you can, taking these supplements may let you do more work, which can make your muscles stronger (Medicine & Science in Sports & Exercise, December 2000).
Promoters of these supplements recommend doses of 6,000-10,000 mg per day and most athletes who use them take far more than that. Half of the athletes who took double the recommended dose suffered adverse side effects, usually nausea, stomach cramps or diarrhea. High doses may drop blood pressure which would harm performance. Blood pressure usually rises with exercise; a person with resting blood pressure of 120/80 can expect it to rise to 200/80 while jogging.
Prescription nitric oxide simulators such as Viagra can benefit men who have difficulty achieving or maintaining erections. Exercise, by itself, raises blood levels of nitric oxide (American Journal of Hypertension, August 2007). So if you want your arteries to make more nitric oxide, go out and exercise.
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