Most people who drink alcohol have experienced the unpleasantness of a hangover. The thirst. The nausea. The headache. The inability to move. Hangovers are primarily caused by the ethanol found in alcohol in the following ways:
During the metabolism of ethanol, the production of NADH increases, which in turn causes an excessive amount of NADH in the body. This build up of NADH attributes to the deceleration of gluconeogenesis (the biosynthesis of new glucose), causing the liver to insufficiently supply glucose to body tissue—especially to brain tissue. This lack of glucose contributes to the effects of a hangover because glucose is the primary energy source of the brain and other tissue.
Impurities found in alcohol (congeners) are also believed to contribute to hangover symptoms. Distilled spirits, in comparison to beverages that are not (beer, red wine, whiskey, etc.), often possess fewer congeners due to the distillation process. Since shochu is a distilled spirit, the impurities are largely eliminated during its manufacturing process, especially Kohrui shochu since it is distilled multiple times.
Honkaku shochu on the other hand, may still possess some impurities, since it is produced using just a single-distillation process, though still far fewer than red wine or beer. This is one reason why shochu has been consistently increasing in popularity over the years: it is a delicious drink and the repercussions the following day are far less severe than other beverages.
Please keep in mind: shochu is still an alcoholic beverage, and like any other alcoholic beverage it must be consumed in a responsible manner. Just because shochu can benefit your health does not mean it won't intoxicate you. Please drink carefully.