I would like to share my experience with n-acetyl cysteine.
About three months ago I bought a bottle of Swanson's NAC and took a third of one 600mg capsule content diluted in water. It had a very sour taste and I felt burning in my stomach after ingesting it. An hour or so later I started to feel tingling and burning in my scalp and face, something what felt like pressure behind my eyes, slight loss of balance (had trouble standing still on one leg), a sort of clumsiness and loss of coordination (I had to type really slowly, otherwise I would miss the correct keys). I also noticed I somewhat sputter when I talk. The tingling and burning sensation reduced in a couple of days, though. I also noticed I craved fatty foods much more than before and disliked anything that had carbs in it. I was eating low carb at that moment but went on a full ketogenic diet from then. Also, certain foods would really aggravate all of the symptoms. For example, lettuce, carbs and especially alcohol. What really helped, especially with regaining balance and coordination was liver (mostly beef liver).
So reading about my reactions, I came to conclusion that I had probably been experiencing nitric oxide toxicity: NAC increases NOS activity and eNOS protein expression (I suppose this means better NO production long after NAC has left the system), FFAs inhibit nitric oxide synthase, insulin acitvates it; lettuce and leafy vegetables are very rich in nitrates, which stimulate nitric oxide production and alcohol acitvates eNOS; liver is the richest food source of vitamin B12, which is a powerful nitric oxide scavenger. It's also possible that the capsule(s) didn't contain NAC but something else.(?)
It did cross my mind that this could all be in my head. I don't know... I tried to maintain a positive attitude and not pay much attention to it, kept myself busy with exams at the university and waited hoping it would pass. However, three months later, I still don't feel quite normal. Some of the tingling in my scalp (I feel it only after I wet my face and head, though???), impaired balance and reactions to the foods I mentioned are still present. Vitamin B12 was shown to be really helpful, didn't use it much in the past weeks because I decided to have my MMA(methylmalonic acid) levels checked (a very expensive testing by the way).
So if anyone finds himself in a similar situation, I hope this helps. Fell free to comment, advise, suggest.
