I was trying to come up with how to ask this and working in the adult entertainment industry alone doesn't seem like it would fit here. But I will ask if you worked in the adult entertainment industry as a graphic designer would you put those pieces in your portfolio? Have to maybe make a "G" portfolio and a statement that a full portfolio including nudity is available? Or do you basically treat it in your mind as 'confidential' and just would put the job on your resume but leave it out of portfolio entirely?
Common sense would indicate that:
If you regularly go for both types then by all means have two separate portfolios and resumes. And if this is the case then you're no doubt already aware by now that some clients may be uncomfortable hiring you if you are open about the "other" work you do - a job in adult entertainment can affect how people outside that industry perceive you. I probably wouldn't even indicate that your "adult" portfolio is available on request, unless you have a good reason to believe that is what they are looking for.
I have to take issue with your choice of question title I'm afraid. There is an immense difference between "nudity" and "adult entertainment" (which I interpret to be about porn/erotica) and had your question been really about nudity, the right answers would be very different. There would not necessarily be any reason to exclude simple nudity from a portfolio.
I'd absolutely never include anything from the adult entertainment industry in any portfolio unless I was applying for another position in the adult entertainment industry.
And I don't say that because it would offend me. I say that because you never know who it will offend.