"For someone who does, it would be very difficult," the 27-year-old defender said.
"An openly gay footballer would be exposed to abusive comments."
But Lahm insists he would feel comfortable playing alongside an openly gay teammate. "I have no problems with homosexuals whatsoever," he insisted.
Lahm's comments are likely to land him in hot water with the German Football Federation (DFB) whose president Theo Zwanziger has called for gay footballers to come out and promised the federation's help.
"I would find it brave and would welcome it if a football player would come out," Zwanziger said in March.
"He would have the support of the DFB and from me."
Last November, Bayern Munich striker Mario Gomez gave an interview – also to Bunte - where he urged gay footballers to come out of the closet.
"They would play as if they had been liberated. Being gay should no longer be a taboo topic," said Gomez, the German league's top-scorer last season.
He added that there were plenty of role models in German society to inspire gay players to come out including Foreign Minister Guido Westerwelle and Berlin Mayor Klaus Wowereit.
And Germany goalkeeper Manuel Neuer, who plays for Champions League semi-finalists Schalke 04, has also said homosexual footballers should feel free to go public.