I believe most of those claims came from The Private Life of Chairman Mao by Li Zhisui. Li served for a time as Mao's personal physician. Many of the claims in the book have been disputed, not only by the CCP (of course), but also by historians and sinologists in the West. The main issue is that his claims are difficult to substantiate.

You can get a basic intro into the controversy through the wikipedia page linked above. Hopefully someone else can chime in with some deeper reading on the subject.