Wikipedia takes a skeptic's view of Walker and says he died at 99. There's some evidence that's correct. It's also consistent with this 1933 New York Times account of a Norman Walker who ran a Brooklyn Institute of Ortho-Dietetics and was found guilty of bilking the institute's students out of $150 in tuition. That Norman Walker was 46 at the time; he would have been 99 in 1985.
Walker himself was circumspect about his age. In 1972, he wrote: "How old am I? I am ageless."
He was, however, forthcoming about the cause of his longevity (however long it was). For most of his life, Walker sold juice and the promise that a diet of raw foods—particularly in liquid form—were a source of health and wellness.
One of the founders of today's juice movement, Walker was born in Europe but immigrated to the United States as a young man. He eventually made his way to California, where he opened a juice bar, and then to the southwest, where he churned out a series of health books. At some point, he started calling himself Dr. Norman W. Walker, although it's unclear when he earned the Ph.D. he said he had.