These Categories are used mostly in restaurants, food labeling, medical procedures, Genetical procedures and Cybernetics.
The DNA Helix can turn clock wise or counterclockwise (right or left) and Sugar molecules also can turn left or right. A being with left turning sugars can only consume foods that break down to left turning sugars, the cells can use and metabolize into energy.
Approximatley 70% of the Union Population has left turning DNA and required Left Sugars. But this percentae is shrinking every year as more civilizations join, especially from the Andromeda Galaxy where it seems Right turning DNA prevails.
Regional Supermarkets and Food stores keep the right food in stock. But at space ports, travel centers, hotels and such this factor is important (and partof the data stored on the CITI chip)