Evidence Studies of ginseng have shown varying effects and limitations and include the following: Enhancement of immune function via modulation of inflammatory cytokines (1) Anticarcinogenic effects (2) Decreases in blood glucose (3) Improvement of cognitive function (4) Fatigue (5) A systematic review of 5 studies (747 subjects) found no evidence that ginseng decreased the incidence or severity of colds, but ginseng did shorten cold duration (6).