Probably so unless they also take special supplements. I remember reading an article about Bill Walton ... he had gone vegetarian in the 70s and ended up with a severe magnesium deficiency. Once the doctors learned that Walton's vegetarianism wasn't based on "don't want to kill animals" but rather on "this is healthy, isn't it?", they told him to go eat a frickin steak every few days. He did; no more magnesium problems since.