My quote answers the question of "why don't we all supplement with L-arginine long term" with "it's in basically all protein containing-foods, so it is not necessary".
While you are right there may be individual variation, the rule of medical advice is that we cannot assume what we do not know, and preventative ingesting of a substance that is not too well understood may have unintended side-effects. Especially in the case of molecules that have been synthesized.
As my other comment within this thread states, there is a high precedence for contamination of health supplements as a whole, so in this instance preventative dosing would seem to put someone at more risk than e.g. just eating more protein.
In addition, the supplements may contain vastly higher quantities than are safe to absorb. For example, there was a recent pubmed paper describing an incident where +500mg doses of Vitamin C (which is 1/6th of the EFSA and NIH's estimates of "safe upper limit") taken daily over a long time caused kidney stone formation. This required expensive surgery to correct.
For what it is worth, as someone with a damaged and resectioned gastrointestinal tract -- the dieticians I work with prefer to solve deficiencies with eating foods that contain the given micronutrients rather than supplementing with them. One doctor told me I had a copper deficiency, he told me that taking copper supplements tends to cause gastrointestinal distress and would have been too high a correctional dose, and so his solution was to increase my consumption of dust (which is how we naturally get copper) through obeying the five second rule. This wasn't especially out of the norm. Selenium deficiencies were solved by eating tinned tuna, likewise vitamin B12 deficiencies were solved by ingesting liver occasionally, etc.
If you suspect that you are deficient in a given micronutrient, it is always better to explore that possibility with your doctor than to take high quantities of unreliably tested substances.
While you are right there may be individual variation, the rule of medical advice is that we cannot assume what we do not know, and preventative ingesting of a substance that is not too well understood may have unintended side-effects. Especially in the case of molecules that have been synthesized.
As my other comment within this thread states, there is a high precedence for contamination of health supplements as a whole, so in this instance preventative dosing would seem to put someone at more risk than e.g. just eating more protein.
In addition, the supplements may contain vastly higher quantities than are safe to absorb. For example, there was a recent pubmed paper describing an incident where +500mg doses of Vitamin C (which is 1/6th of the EFSA and NIH's estimates of "safe upper limit") taken daily over a long time caused kidney stone formation. This required expensive surgery to correct.
For what it is worth, as someone with a damaged and resectioned gastrointestinal tract -- the dieticians I work with prefer to solve deficiencies with eating foods that contain the given micronutrients rather than supplementing with them. One doctor told me I had a copper deficiency, he told me that taking copper supplements tends to cause gastrointestinal distress and would have been too high a correctional dose, and so his solution was to increase my consumption of dust (which is how we naturally get copper) through obeying the five second rule. This wasn't especially out of the norm. Selenium deficiencies were solved by eating tinned tuna, likewise vitamin B12 deficiencies were solved by ingesting liver occasionally, etc.
If you suspect that you are deficient in a given micronutrient, it is always better to explore that possibility with your doctor than to take high quantities of unreliably tested substances.