Carotenoids are plantbased compounds that may have diseasepreventing properties, and grapefruitespecially pink and redcontains more than its share of them. Grapefruits carotenoid phytonutrients, an antioxidant called lycopene, may have chemoprotective effects. In a clinical study published in the March 2005 issue of International Journal of Cancer, researchers found that prostate cancer risk declined with increased consumption of lycopene. According to Texas A & M University Extension, 3.5 ounces of pink grapefruitabout half of a small grapefruitprovides 3.36 mg of lycopene. Vitamin Herb University notes that estimating daily intake of lycopene is difficult due to variability in foods, but suggests most people consume from 3.7 to 6.5 mg per day.