What is the difference between sugar and sugar alcohol?

Complex chemistry: The correct answer to this involves basic knowledge of carbohydrate biochemistry. Sugar alcohols are hydrogenated forms of carbohydrates. Some simple sugar alcohols are toxic (such as ethylene glycol [antifreeze]), others can be used as food sweeteners, but they are mostly much less sweet that sucrose, which is common table sugar.

Sugar alcohols: The funny thing about sugar alcohols is that they reconstitute into actual sugar once digested. So a product can be marketed as "sugar-free" if it contains sugar alcohols, but after absorption there's sugar again. It's a marketing ploy. So yes, sugar alcohols can have bad effects on your body just like sugar.

Sugar alcohol?: Sugars are simple carbohydrates-single or double sugars. Sugar alcohols like sorbitol, maltitol, etc. Are naturally occurring compounds poorly digested by humans, but fermented by normal gut bacteria. Non nutritive, but sweet tasting. Can cause gas, bloat, cramps, diarrhea when taken in excess. Listed as "sugar alcohol" on "nutrition facts" of packaging.