1) It indeed seems the 'L-lysine/L-arginine'-combo is what is usually recommended (as opposed to taking solely L-lysine OR L-arginine). However, anxiety is apparently related to L-lysine deficiency. Why shouldn't one just supplement on L-lysine then? (This confuses me the most..)
I have read that too about l-lysine being used for anxiety as a stand alone.I honestly dont know, maybe you could try the l-lysine on its own first, observe the effects and if it does not provide the relief required add in the l-arginine. There is not a lot of research on this treatment, maybe four studies tops. Further research is definitely needed I think, given the positive results that the studies achieved and me myself of course.
2) Looking at the foods that are high in L-lysine and those that are high in L-arginine it seems rather unlikely one would develop some kind of deficiency in either one. (I know at least for myself that I am consuming a lot of foods on both ends of the spectrum; and even if I would be deficient in any, it would more likely be L-arginine than L-lysine.. ~since I largely avoid wheat and gluten. Still, I do experience quite some anxiety/stress issues)
What could be the reason that people develop a deficiency/imbalance in these amino acids?
From what I have read, under stress, l-lysine is one of the first nutrients in the body to become rapidly depleted,among others of course. I suppose it could be like any deficiency that is aggravated by stress,even if you are consuming large amounts in food it may not be enough when confronted by a barrage of stressful situations, especially if a person is continually anxious. I eat a lot of high zinc foods and supplement with zinc but I am still zinc deficient,you get the idea.
3) Any thoughts on side-effects and possible long-term negative effects?
No negative side effects to report at all,if anything they are all positive. My period is due in 3 days time and normally I am like a demon with crazy mood swings and anxiety and would be reaching for a benzo at this point. Instead I am cool, calm and collected! This is the latest side effect I have noticed. Apparently this combination helps to regulate the endocrine system too, as a side effect of regulating the stress response.
Again from what I have read, there are no recorded long term side effects except if taken in quantities exceeding 10g I think of each a day but there is no need for that amount.
With regard to dosage, I find that taking 2g of each first thing when I wake up sets me up nicely for the day, I will then pop another gram of each around midday which is when I get a little tired and it perks me up. I also found that the supplements interfere a lot with my sleep though Im sure everyone is different. I have read that it actually encourages and improves sleep in certain people. I wont take any past 6pm though thats just me. That said, I take seroquel as a sleep aid and I think there could possibly be some crossover there. But if you can tolerate it at night great, I think I read that it actually works even better taken at night. Hope that helps, Im no expert, just reporting on my own research and experiences :)