These are natural plant-based chemicals found in healthy foods.  They come under the broader category of phytochemicals which basically refers to any plant based chemical.  Strictly speaking polyphenol should come under category of flavonoids (see below) but they are generally used to describe any phytochemical which has potential health benefits. In the past, they were often referred to as anti-oxidants but this relates to only one of their potential properties which potentially can have an impact on health. Polyphenols also include the category of plant based chemicals which have weak hormonal effects known as phytoestrogens.

A full scientific review of polyphenols and Cancer can be downloaded here.

There are hundreds of different polyphenols known to mankind and attempts have been made to separate them into categories although their properties over lap and are present in a wide variety of foods to greater or lesser concentrations. Here are some examples of the more commonly recognized categories:

Carotenoids:

  • Beta-carotene (carrots, peaches, apricots, spinach and cantaloupe)
  • Alpha-carotene (carrots and pumpkins)
  • Cryptoxanthin (oranges, papaya, peaches and tangerines)
  • Lycopene (tomatoes, chilli, watermelon and pink grapefruit)
  • Lutein (Spinach Kale, red pepper, Okra
  • Zeaxanthin (corn, broccoli, spinach, red pepper, peas, kale,  celery)

Natural Monopherols:

  • Apiole (Parsley)
  • Carnosol (Rosemary)
  • Dillapiole (Dill)

Organosulfides:

  • Isothiocyanate and its metabolite sulforaphane (Broccoli)
  • Diallyl disulfide (Garlic)

Flavonoids:

  • Isolavone phyooestrogens, e.g. Daidzein, Genistein, Glycitein (Soy, peanuts, legums)
  • Flavonols e.g. Kaempferol (broccoli and other cruciferous vegetables)
  • Flavonol polymers e.g. Catechin (cocoa and Chocolate)
  • Flavan-3-ols (epigallocatechin gallate (EGCG) – green tea)
  • Stilbenoids  e.g resveratol (grapes and red wine)

Phenolic Acids:

  • Chlorogenic acid (coffee)
  • Ellagic acid (Pomegranate, raspberries and strawberries)
  • Benzoic acids (hydroxybenzoic acid, gallic acid)
  • Cinnamic acid (apples, wheat, articoke)
  • Salicylic acid (bark of Willow trees most fruit and veg)

Nonflavonoid phenolics

  • Curcumin – a root herb
  • Capsaisin – chilli
  • Piperine – pepper

It is clear from this list that foods with the highest polyphenol content include, herbs, spices, teas, fruit, vegetables berries, prunes, flaxseed, linseeds, nuts, dark greens, cruciferous, brightly coloured vegetables, berries, fruits and grains and nuts.