Alright everyone, pull out your human biochemistry textbook and follow along! In other words, if you hate opinions that are largely derived from scientific literature, just skip this post. You'll just end up flaming me, and I'm too delicate to handle that. *smirk*
The main premise behind using NO-stimulators is based upon boosting blood-arginine levels (from either L-arginine or arginine-alpha-ketoglutarate) which will, in turn, boost blood-NO levels. Considering ARG is a substrate for NO, this is somewhat plausible. NO will then, supposedly, act as a vasodilator, increasing blood flow and nutrient delivery to muscle cells. Reasonable, right?
Unfortunately, there is simply too much evidence to go against this idea. It can actually be refuted in a single statement: The concentration of baseline arginine that exists in the bloodstream is far, far greater than the maximum amount that can converted into nitric oxide. Rather, human biochemical response dictates that instead of converting ARG to NO until equilibrium is reached, a catalyst is required in order to signal this reaction to take place. In other words, we have a huge bank of serum arginine in circulation; boosting NO levels results from signaling the ARG --> NO reaction to take place. Boosting blood-ARG levels is futile, as we have plenty of that substrate without additional supplementation.
However, when you examine the destiny of ARG in the body, you see that ARG is a potent insulin secretagogue. Likewise, insulin is a potent promoter of temporary NO conversion, and thus a vasodilator. So... the insulin response associated with ARG-based products is what causes the NO boost, not the actual ARG substrate. In fact, a study conducted at Penn State showed that blocking receptors on the pancreas (and hence, stifling insulin secretion) reduced NO increases by about 80% following ARG supplementation. A subsequent study from 1999 demonstrated that glycogen replenishment in a semi-fasted, post-workout scenario was accomplished 3x faster with a whole-protein/carbohydrate combination than with an ARG/carbohydrate combination.
Beyond this, it is well known that amino uptake is somewhat ineffecient in administration of single amino acids. Amino acids seem to rely on the prescence of others for effective uptake. The free amino acid pool generally operates with a degree of homeostasis. Ingesting megadoses of a single amino acid will shatter this equilibrium, thus forcing expulsion. It is far more effective to raise insulin levels with a combination of carbohydrates and whole-protein than by carbohydrates and a single amino.
So, by this evidence, NO-boosting supplements are somewhat effective, even though they work by a mechanism other than what is claimed. There is much more effectiveness (particularly, cost effectiveness) in implementing a solid post-workout carb/protein combination. NO-boosting agents simply work by manipulating insulin flux. This can be done, quite easily, by dietary methods. By this standard, I find it simply foolish to invest so much money into an inefficient secretagogue. It is comparable to using a saline IV as a hydration source. Sure, it works, but there is a much easier, cheaper way to get water. So yes, it works, but very, very inefficiently.
