I always heard that spinach should be cooked if you are to get any nutritional value from it. To tell you the truth though, I have never found any real proof of this statement. What I did find on Google was this info:

"Spinach has only 13 calories per serving and packs a punch for Vitamin A as well as folic Acid (especially important for pregnant women) and is rich in carotenoids and antioxidants. It is also rich in chlorophyll. Debate exists whether it is more beneficial to cook spinach or eat it raw (juice it). Spinach contains oxalic acid. While this cleans our intestinal tract, oxalic acid binds with calcium and diminishes the absorption of calcium in our bodies. Cooking turns the oxalic acid into crystals that could damage kidneys and limit the absorption of iron but cooking also breaks down cell walls and allow us to absorb more nutrients. The answer? Eat spinach in moderation, and eat it raw as well as cooked."

The good thing about eating raw spinach is that it is very high in fiber. Unless all you are eating is raw spinach I really wouldn't worry too much about not getting enough vitamins and minerals.