How did my nephew survive by eating nothing but peanut butter sandwiches?

Since the day my nephew was born, he has lived on nothing, but peanut butter sandwiches. Not just for one meal, but for breakfast, lunch and dinner. My brothers house was loaded with Skippy peanut butter jars, just to accomodate his son, my nephew. He grew up healthy and was given a multiple vitamin daily to compensate for his lost nutrition, due to peanut butter sandwiches eating, only. Question: as a child, my nephew was never sick and thrived to be an adult, just on peanut butter and bread. Was my nephew obsessed with peanut butter?