I'm all about whole foods and a balanced diet, and think that if one eats right, there isn't need for vitamins, et al. But and except, when we push beyond a balanced lifestyle. For me, my Ironman training and racing isn't normal stress on the body, and my body has nutritional needs well beyond a sedentary person. Personally, I can feel a difference if I do a 100 mile ride or 20 mile run, say, and do or do not take my particular nutrition cocktail. As they say, one doesn't win the Tour on bread and water alone