Tapioca Flour

One of the ingredients I have bought for gluten free cooking is Tapioca Flour (which may also be called Tapioca Starch). This flour was recommended to take the place of corn starch in many recipes.
But what is a tapioca? According to my "extensive" research involving looking it up on Wikipedia...
Tapioca is "an essentially flavourless starchy ingredient produced from treated and dried cassava (manioc) root and used in cooking." Cassava is a nifty little root looking something like a sweet potato and used similarly to potatoes or sweet potatoes. It is high in starch, calcium, phosphorus, and Vitamin C. Cassava is especially important in agriculturally poor nations as it "gives the highest yield of food energy per cultivated area per day among crop plants."

The nutrient facts for my Ener-G brand Tapioca Flour are for 1/2 cup of flour: 170 calories; 0g Fat; 0g Protein; 42g Carbs with 0g Sugar. Apparently, all the wonderful benefits of calcium, phosphorus, and Vit C have been processed out by the time cassava becomes tapioca because these are not present in my flour.