Mitogenic factors released by platelets, such as platelet-derived growth factor (PDGF), are thought to be important in the initiation and progression of atherosclerotic lesions and to respond to alterations in diet (75). Ross et al (75) detected increases in serum PDGF-AB concentrations (adjusted for platelet concentrations) when study participants consumed diets high in carotenoid-rich vegetables (carrots and spinach) and soyfoods (tofu and textured soy protein). Cruciferous vegetables (broccoli and cauliflower) did not increase PDGF-AB above baseline, and none of the diets changed mitogenic activity. Until the complex feedback mechanisms that regulate growth factors have been worked out more completely in humans, the biological significance of these observed effects is not clear; however, this may be an additional mechanism by which vegetables may influence disease risk (75).