Added sugar is the single worst ingredient in the modern diet. It can have harmful effects on metabolism and contribute to all sorts of diseases. Here are 10 disturbing reasons why you should avoid added sugar like the plague. 1. Added Sugar Contains No Essential Nutrients and is Bad For Your Teeth You've probably heard this a million times before... but it's worth repeating. Added sugars (like sucrose and high fructose corn syrup) contain a whole bunch of calories with NO es