I have no idea if there are any studies. It's a very subtle difference. I would describe it as a certain... crispness. A mild hum of well being in the back of

I have no idea if there are any studies. It's a very subtle difference. I would describe it as a certain... crispness. A mild hum of well being in the back of the brain. Like lifting the very light blanket of an endless hangover; a blanket so light you don't notice its presence, only its absence. Of course--and as usual for this sort of thing--lots of confounding factors, N of 1, YMMV, etc etc