Research has not demonstrated a very positive effect with supplements of polyphenols. This study shows that the most benefit of polyphenols for cancer prevention and oxidative stress reduction comes from them working together. Their benefits are more potent together compared to their activity individually!
The anti-cancer effects of carotenoids and other phytonutrients resides in their combined activity. Archives of biochemistry and biophysics, Vol. 572 (15 April 2015), pp. 28-35 by Karin Linnewiel-Hermoni, Marina Khanin, Michael Danilenko, et al. http://www.citeulike.org/user/kimberlykramer2015/article/13593243
