A recent study on dietary interventions aimed at lowering cholesterol divided participants into three groups. Each group consumed the same diet, except that one ate one red grapefruit daily, the second ate one white grapefruit, and the third ate no grapefruit at all. After only one month, there were no differences in the heart rate, blood pressure or weight of the three groups. Antioxidant activity in both white and red groups was increased compared with the group that ate no grapefruit. But the group that ate red grapefruit every day also had significantly decreased blood levels of triglycerides. Although it is common knowledge that grapefruit and other citrus fruits contain antioxidants that help control lipid levels, the researchers can't explain what components of red grapefruit make it so much more effective than other varieties.