Jack LaLanne was not a vegan most of his life, although it's true that he avoid anything that comes from a cow, including dairy and the cow itself. In an interview he gave at the age of 91, he had the following exchange with interviewer Dennis Hughes of Share Guide (http://www.shareguide.com/LaLanne.html):
Share Guide: In your book you mention that you were a vegetarian at one point for 6 years.
Jack LaLanne: I was a strict vegetarian. Then I decided to enter a Mr. America contest (which I won) and in those days they thought that in order to build muscle you had to have meat. So I ate meat for a while.
Share Guide: Why did you stop being a strict vegetarian?
Jack LaLanne: In those days everybody was saying that you had to eat meat to build muscle, so I went on a meat thing for awhile. Now I only eat fish--no chicken, no turkey, just fish. I get all my protein from fish and egg whites.