What is a major effect of alcohol on the body? Question What is a major effect of alcohol on the body? Answers It slows down and impairs bodily functions. It speeds up the drinker's reaction time. It improves the drinker's judgment. It usually doesn’t have an effect unless the drinker is drunk. Explanation Alcohol is a depressant that slows and impairs bodily functions, both mental and physical. Impairment begins after just one drink.