Did you know that most of the fiber and antioxidant properties of plant foods are found in the peels? (An article here). Colorful outer surfaces of plants come from pigments that are very beneficial to our health (flavonoids, carotenoids). Also, plants cannot run from predators and pests that want to eat them, so they use chemicals and barriers to repel attackers. Fibrous rinds and bitter chemicals are the ones that help us stay healthy: antioxidants, anthocyanins, theobromides and cellulose and are located on the outsides of the plants where pests attack first. So if you remove the peels from the vegetables and fruit, you are removing most of their beneficial qualities. The flesh of the fruit/veggie is not as nutritious.
What? So #1) This means buy organic, because those peels are going to keep you healthier if there are fewer pesticides sprayed on them. #2) How? Throw the whole washed unpeeled fruit into the smoothie. Wash the veggie and leave the peel on before slicing and dicing, or cooking. Make a stock with the outsides of the veggies.