Please explain more ! I think I know what you mean
well i usually can figure out by trial and error what it is that makes me nauseous or sick.. but yeah i think with this kava in particular, maybe there's something about it that my body has just gotten so used to that it says "nope, not good anymore." i would get the same way in the past with different types of alcohol. the vanuatu kava supreme is very strong and i'm pretty sure that's part of it. i started on and prefer the mellower kavas, so it makes sense that i have trouble with it.
also, i've looked into the whole nobility/adulteration thing and man is it a rabbit hole. apparently all kava has some level of adulteration (of what is typically referred to as tudei but even that is a vague term). and some "noble" kavas are more "pure" in a sense than others. i don't know where this kava is on that spectrum but i suspect it's not up among the highest. (and not to take anyway from this kava. i still recommend it to people wanting to get into kava because i think it's a great first-time kava) for most people this makes absolutely no difference. they probably don't notice anything negative about it. there are tons of other factors too.. how much kava someone is drinking, how healthy/active they are, etc. that all impacts how you respond to kava i think. i drink kava pretty much every day all day. i will tend to make weaker kava and sip it (gross i know, but i'm used to it). and the extra water i've heard can add to nausea. (interestingly though, certain kavas on the upper end of the nobility spectrum are fine for me to drink even if they are watered down a LOT).
for a while i thought something was up with my straining method, and i did find that when kava starts collecting up your strainer, the kava you make in it will give me a less "clean" buzz. but that was only part of the problem it seemed. i also thought maybe all the extra water i was drinking (i really drink a lot of watered down kava everyday) was causing a slight sodium imbalance in my body or something. (i had a scary "water poisoning" experience a bit ago where i was taking anti-diuretics and i was still drinking kava.. which is a diuretic. had to go to the hospital. and i know that feeling. it starts with nausea and just this weird feeling).
but after everything i only *really* know that there are certain strains i can drink long-ish term (though i'm thinking now that any strain i drink too much of, my body will get "used" to it and i'll need to change things up). and the type of kava is very important for me. honestly my kava friends say i should take a decent length break from kava which yes, i probobly should do.. but i used to drink certain strains of kava daily for around 5 years without any problems. it's tough getting any real medical info about kava and all the subtle ways it affects people. even on here, there's not many people who can explain (adequately) or even relate to my issues. but anyway...
hah sorry for the novel of a reply. this was probably a lot more explaining than you cared for but it felt good to vent a little