What is a left-handed sugar?

Answer 1

"Right-handed" means false, fake, or disguised. Right-handed sugar is referring to sugar substitutes (such as Sweet N Low, Splenda, etc): fake sugar disguised as real sugar. Used by diabetics or people trying to cut back on sweets.

Actually "Right-Handed" when referring to sugars can be referring to the chilarity, or "handedness" of the molecule itself. In all natural sugars the molecules are wound in a particular direction (think of the 3d models you see in museums). All natural sugars are built with "Left-Handed" chilarity. The idea behind building a "Right-Handed" sugar molecule is that the taste will be the same but the body will be unable to process it as a sugar. Thus no tooth decay, weight gain or any other of the negative side affects associated with sugar consumption.

Something to note on the issue of chilarity is that the issues caused by thalidomide came down to the "handedness" of the molecules. While the "Left-handed" molecules did indeed prevent nausea as described, the "right-handed" molecule caused the fetal abnormalities (these left-right distinctions may be swapped).