That's one of my favorite questions, because it really sums up the dichotomy between modern medicine and traditional care of the body.
Yes, your body more or less runs on glucose, and yes, sugar is composed of glucose and fructose. Therefore it technically does contain this necessary ingredient in a very simple, easy form; it also supplies a large number of calories in a small package. Sounds ideal, doctor.
Unfortunately, when you remove the terms "glucose" "sugar" and "calories" from the vacuum in which we just spoke of them, you find that "food" equals more than just "glucose" and "calories" and that your body needs a great deal more than just "sugar" to function properly.
Your body needs a broad spectrum of nutrients, vitamins and minerals, without which it cannot properly regulate your blood sugar (or anything else for that matter). Sugar has no vitamins, minerals, or nutrients of any sort. That's why you've often heard it referred to as "empty calories". Our body gets more than enough sugar from the carbohydrates we eat, be they grains, vegetables or fruits. It has no need whatsoever for any sugar other than what is already contained in these whole foods that also provide it with necessary vitamins, minerals and fiber.
One of the worst things you can do for your body is to feed it with foods that have been stripped, denuded and denatured, which covers everything from white rice to white flour to hydrolyzed anything to partially hydrogenated anything. Our bodies cannot use these substances, nor can it clean them up and get them back out of your body without using up a lot of vitamins, minerals, etc.
Bottom line: when you eat nutrient-depleted foods, not only do you not get nutrients from them that your body needs, your poor body has to use what nutrients it has stored up (if any) to clean up the mess the nutrient-depleted "foods" make inside your body.
Nike says "just do it"
Your body is God's temple, and it says "just stop it!!!"