The white crystalline substance we know of as sugar is an unnatural substance produced by industrial processes (mostly from sugar cane or sugar beets) by refining it down to pure sucrose, after stripping away all the vitamins, minerals, proteins, enzymes and other beneficial nutrients.
What is left is a concentrated unnatural substance which the human body is not able to handle, at least not in anywhere near the quantities that is now ingested in today's accepted lifestyle. Sugar is addictive. The average American now consumes approximately 115 lbs. of sugar per year. This is per man, woman and child.