I'm big on breakfast smoothies too. I saw a nutritionist while being treated for prostate cancer and they RECOMMENDED fresh fruits and vegetables. I suppose if you ate fruit all day long it might not be the best idea, but fruit is high in vitamins and fiber, both of which are good for you.

Sometimes, I put spinach in the smoothies. It's packed with nutrition and has minimal taste when mixed with other things. It just makes the smoothie look weird. Occasionally, an avocado is good in a smoothie as well. It makes it very creamy and delicious.