The Perils of Grapefruit Juice Studies have demonstrated that grapefruit juice (a level of one independent variable) can interact with many common medications (levels of a second independent variable) to cause higher levels of active ingredients (the dependent variable) to be absorbed into the bloodstream. The medical journals that physicians read report the results of such two-way ANOVAs because interactions have the potential to be toxic. This is why some physicians recommend that patients who take certain medications avoid grapefruit juice entirely.