"First, I am not a homosexual. I am not married to my wife Claudia for appearances and I do not have a friend in Cologne with whom I really live," Lahm wrote in the book entitled "A Subtle Difference."
"This speculation doesn't matter to me," he said refering to rumours about a male companion in Cologne. "I have nothing against homosexuals and I find that there is nothing wrong with homosexuality."
"But it never ceases to amaze me that these isolated types, who tell these stories, can have a lot of influence on public opinion. 'Philipp Lahm homosexual' (...) do you not have anything more important to talk about?" he said.
He however advised professional footballers against coming out, referring specifically to Justin Fashanu, the first professional player in Britain to publicly reveal his homosexuality.
Fashanu, who, after his disclosure, spoke about deep-seated anti-gay prejudice in professional football, killed himself in 1998.
"A Subtle Difference," on sale in book stores Monday, is the Bayern Munich star's first book.
It has for several days been hotly discussed around Germany, notably for Lahm's criticism of some players selected to play on the German national team, including picks made by current coach Joachim Löw.
Lahm has apologized for the criticisms and Germany's national football organ (DFB) has indicated that he will remain captain.
Lahm was named captain in 2010, and led the side to a third-place finish in the 2010 World Cup in South Africa.