I don't think any researcher to-date has ever had any clinical evidence of NO deficiency. My theory which I stated last year and which has evolved over the past year is that we have NO dysfuction, stemming from Endothelium tissue damage. We have 4 tissue layers in our body Muscle, Nerve, Connective and Endothelium. Endothelium tissue regulate NO and there are much more neurotransmitters involved in activating the endo release it as well... Further I think the damage is not necessarily in every organ for all of us. Depending on were the main damage is, that's how our main symptoms manifest. This also can mean there is too much NO in one are and not enough, basically our NO is off balance in certain organs.. There dose seem to be more people who would have too high NO overall than have too little, but it depends on a lot of things. Well it's complex and if I were supplement, it might help one area but bother the rest of the body that's normal or high... For example people with pulmonary hypertension maybe have normal BP but only in their lungs they have high BP. So if you gave them supplements if would bring down their normal systemic BP too low. So with Pulmonary hypertension they pipe pure NO directly to patients lungs all day long. No has a very short half life...