Due to low absorption polyphenols are held to be poor in vivo antioxidants. The idea that is being put forward is that what happens in the gut can have systematic affects. The antioxidant and iron chelating properties of polyphenol compounds in the gut can have large effects on aconitase 1 in the gut and other enzymes in the TCA cycle in the gut with systematic effects then occurring. Polyphenols are not well absorbed, however, polyphenols do not have to be well absorbed to have large systematic effects. Polyphenols are everywhere in plant based foods. Difficulties only arise with polyphenol extracts such as natural flavors and foods processed to have concentrated polyphenols such as spices, sodas, coffee and tea.
If someone is healthy not taking supplements and eating balanced meals is an excellent health strategy. There are lots of pitfalls with supplements. The worst way to take supplements is to follow the scientific evidence but disregard fails in clinical trials. If there is lots of scientific research in an area but clinical trials have not panned out there are very serious unknown factors that make a strategy a dangerous strategy. Take for example, antioxidants. There is tons of scientific evidence that oxidant stress is a major difficulty in many illnesses but clinical trials of antioxidants have not shown supplemental antioxidants to be useful in the treatment of chronic illnesses. Antioxidants should work but don’t work adds up to don’t try at home what has been shown to be a fail in clinics. Supplemental folic acid can be dangerous. Folic acid is another supplement that should work but clinical trials have not shown supplemental folic acid to be helpful where there are high homocysteine levels though, of course, women should take folic acid as MDs recommend to prevent neural tube defects in babies. My ideas adhere to scientific evidence, however, my ideas have not been clinically proven wrong.