Jean-Louis,

> Suppose also that X is in the flesh, and Y in the skin. So, why not
> eat X alone, instead of burdening the body with substances it doesn't want?

That is what we are trying to do. We would not eat the skin
on principle but rather because it tastes good or because
the flesh tastes better with the skin.

BTW: I do a similar thing with wild Durian from Bali: I eat
the nuts together with the flesh because I like the taste.
And when the nuts begin to taste soapy or bad, then that
is a good indicator of the instinctive stop, for me.

> I can see no advantage in eating them, except for the reasons I mentioned
> (more abrupt taste change, digestibility,...). My hypothetic fruit,

I think that the 'toxins' in the skin might sometime even be
useful for the body. They might contain the stuff that it
needs to control a virus or bacteria or whatever or to
synthesize something else.

-Karl