While the polyphenol content of fruits usually refers to extractable polyphenols, new research published in the Journal of Agricultural and Food Chemistry reports that the non-extractable polyphenol content is up to five times higher than extractable compounds.
According to studies with apple, peach and nectarine, previous measures to quantify polyphenols may have been limited by the extraction technique.
"These [non-extractable] polyphenols need to be treated with acid to extract them from the cell walls of fruit in the lab," said lead author Sara Arranz from the Spanish Council for Scientific Research (CSIC) in Madrid. "If non-extractable polyphenols are not considered, the levels of beneficial polyphenols such as proanthocyanidins, ellagic acid and catechin are substantially underestimated."
I asked Dr. Fuhrman about this and his quick answer was, “Repeat after me, fruits, vegetables, seeds, nuts and beans! When you eat whole foods, you get much more than science has been able to measure so far.” And here Dr. Fuhrman explains why foods like green vegetables are so healthy:
While fruits and vegetables are excellent sources of nutrients, the consumption of vegetables is more helpful in reducing cancer because they contain much higher amounts of cancer-protective compounds--especially green vegetables. Among these green vegetables, the cruciferous family has demonstrated the most dramatic protection against cancer. Cruciferous vegetables (broccoli, brussels sprouts, cauliflower, kale, bok choy, collards, arugala, watercress, and cabbage) contain a symphony of phytonutrients with potent anti-cancer effects.
Isothiocyanates (ITCs), which are perhaps the best studied, have been shown to provide protection against environmental carcinogen exposure by inducing detoxification pathways, thereby neutralizing potential carcinogens. These vegetables also contain indole-3-carbinol (I3C). Indole-3-carbinol has been shown to reduce the risk of breast cancer by decreasing estrogen activity.