Polyphenols

Definition

Polyphenols constitute a family of hydrosoluble organic molecules, which are very common in plants. They are characterized by the presence of several phenolic groups which are assembled into more or less complex structures (of high molecular weight in general). These substances are used by the plant in its self-defense reactions, against the environmental attacks.

There are several families among which the most famous are flavonoids and tanins. The four main groups of flavonoids are: flavons with quercetin in particular (the most studied flavonoid), flavonons, flavanols (catechins in particular) and anthocyanins. Resveratrol, which belongs to the family of stilbenes, is also a famous polyphenol, particularly for its use in cosmetics.

Role in the body

Antioxidants : their role of natural antioxidants allows to avoid cell oxidation and thus to fight against cell ageing. This is quite important for the prevention and treatment of cancers, inflammatory, cardiovascular and neurodegenerative diseases.

Protective effect against hormono-dependant diseases such as osteoporosis.

Gustatory and visual functions : among flavonoids, flavonons are the origin of grapefruit biterness, tanins cause the astringency of several fruit (grape skin and seeds) and anthocyanins are the cause of the colour of red fruits.

Sources in vegetables and other foods (Source: Ciqual)  

CHAMPION OF POLYPHENOLS : KAKI with 1g/100g of polyphenols

Food with the highest polyphenol content : tea (green or black), grape, soya, red fruits (blackcurrant, blueberry, cherry…)

Food with the highest rate of :

quercetin: capers (181 mg /100g), crude hot yellow pepper (51 mg/100g), cocoa powder and  crude red onion (20 mg/100g), wild blueberry (18 mg/100g), blackcurrant (6 mg/100g), crude apple with the skin (4,4 mg /100g), crude broccoli (3,2 mg/100g)

catechins: green tea (65,7 mg/100mL), black tea (49,5 mg/100mL)

anthocyanins : aubergine (750 mg/100g), cherry (350-400 mg/100g), blueberry and  redcurrant (80-420 mg/100g), mulberry (115 mg/100g), red grape (30-750 mg/100g)

resveratrol : grape variety pinot noir (until 11,9 mg/L and 5,4 mg/L on average)

Recommended intake

There aren’t any GDA for polyphenols.

On average, we have about 1g of polyphenols every day with our food, which means 10 times more than C vitamin and 100 times more than carotenoids or E vitamin.

Deficiency / Excess

Like all the antioxidants, a deficiency in polyphenols can lead to an excess of oxidative stress, causing cell ageing.

Disadvantages

No negative aspect has been mentionned until now. Moreover, contrary to vitamins, polyphenols aren’t sensitive to oxidation and to light and are consequently well conserved in the food we eat.

Tips / advice from the nutritionist

Polyphenols are likely to polymerise, to precipitate and then, they become visible deposit and they can’t be assimilated. Do not mix them with a source of proteins (such as milk, eggs…) and consume them crude or cooked.

To learn more  

For the most curious, have a look at the database which gives the polyphenol content of fruit, vegetables… on the internet.

http://www.phenol-explorer.eu