What are Polyphenols and Flavonoids?

Polyphenols are present in almost all plants. They are primarily divided into phenolic acids and flavonoids. Polyphenols have many health effects, particularly as antioxidants.

Polyphenols are found in almost all plants. These phytoamines include many colorants, odorants, and flavorings, some fibers, as well as substances with hormone-like effects, also known as phytoestrogens. The main groups of polyphenols are phenolic acids and flavonoids. The former are usually present as tannins in plants, giving some of them a tart taste, e.g., in black tea. Flavonoids are mostly present as colorants (pigments) in fruits and vegetables. They give cherries, grapes, apricots, medlars their red, blue, and yellow colors.

Polyphenols - many effects on health

Polyphenols are not essential for humans, but they have many health effects. Particularly strong are the antioxidant functions. Polyphenols can contribute to the protection against cardiovascular diseases, and some have anticarcinogenic effects.

Polyphenols are (so far) not considered essential nutrients, but their health benefits are no longer in doubt according to recent research. Polyphenols generally have a broad and significant spectrum of effects on our health. They can act as antioxidants, antivirals, antimicrobials, and anticarcinogens, can inhibit inflammation and allergies, and modulate the immune system. A number of epidemiological studies in recent years have shown clear relationships between the intake of fruits and vegetables and the associated risk of heart attacks, strokes, and some cancers.

With a consistently low consumption of fruits and vegetables, the risk of these diseases increases, while with regular high consumption of plant-based foods, the risk significantly decreases. Some flavonoids can particularly protect blood vessels and capillaries, others mainly have antioxidant, but also anti-inflammatory or anticarcinogenic effects. For polyphenols, the investigations of possible health effects have so far been determined only for some substances.

Phenolic Acids

In fruits and vegetables, phenolic acids are mainly present in the form of cinnamic and benzoic acids. They have antioxidant and partially anticarcinogenic effects and can contribute to the protection against heart and cancer diseases. Phenolic acids include, for example, caffeic acid from coffee and ferulic acid from grains and rice (both cinnamic acid derivatives), and ellagic acid (benzoic acid derivative) from green tea. The heart-protective effect is probably based on the ability of some polyphenols to prevent fat oxidation and reduce the agglutination of blood platelets. Ellagic acid can probably destroy or block genetic damage caused by carcinogens, such as from cigarette smoke or polluted air.

Flavonoids

Flavonoids are the most common polyphenols in plants. Many of them are colorants. They have antioxidant and partially hormone-like effects.

Polyphenols are most commonly present as flavonoids, often also called bioflavonoids, in food. They are a group of water-soluble plant pigments that give many fruits and vegetables, as well as herbs, their bright colors. About 4000 flavonoids are known today. They are divided into various subgroups, although the classification is not always consistent. One way of differentiation is based on structural differences into six groups, each comprising several substances:

Although structurally similar, the individual flavonoids differ in their functions. Among the most well-known flavonoids are quercetin from onions and genistein from soybeans. The two citrus flavonoids, hesperidin and rutin, have also become increasingly known for their health functions. Recently, ellagic acid (epigallocatechin gallate) from green tea has gained medical attention for its anticarcinogenic effect.

The potential health effects of polyphenols

Epidemiological studies show that regular consumption of a lot of fruits and vegetables can reduce the risks of cardiovascular and some cancer diseases. This is probably also due to the content of polyphenols.

• Reduced risk of heart diseases and strokes
• Strengthening of blood vessels
• Strengthening the immune system (e.g., against viral infections)
• Reduced risk of cancer
• Protection against age-related visual impairments (macular degeneration, cataract)
• Relief of hay fever, sinusitis, and asthma symptoms
• Relief of inflammatory processes (skin, joints, muscles)
• Relief of menopausal symptoms (e.g., hot flashes)

Polyphenols - varying content

The content of polyphenols and flavonoids can vary greatly in fruits and vegetables. It depends, for example, on the plant variety, climate, and harvest month. In the fruits and vegetables available in our region, flavonols are most common. They are particularly abundant in broccoli, endive, kale, onions, cranberries, tomato juice, red wine, and black tea (over 50 mg per kg). The content is slightly lower in orange juice, brewed coffee, tomatoes, apples, cherries, and grapes (between 10 and 50 mg per kg).
Free-range plants generally contain higher amounts of polyphenols than greenhouse plants. Also, the distribution of polyphenols within the individual plant is different. They are much more concentrated in leaves and outer tissue layers, for example, in carrots, celery, horseradish, beet, and radish, than in the roots. Wherever possible, the peels of fruits and vegetables should be eaten. During preparation, many flavonoids prove to be quite heat stable. Some even fully develop their effect only when released from the cell wall by heating. So, the good old canning of compote is quite recommendable and a healthy dessert.

Polyphenols - safe phytoamines in intake

With our food, we consume several grams of polyphenols daily. Regular consumption of fruits and vegetables provides these phytoamines in ample amounts. Polyphenols, especially flavonoids, are contained individually (e.g., red wine polyphenols), as a complex (e.g., quercetin, rutin, and hesperidin), or in combination with other nutrients (vitamins, etc.) in many dietary supplements. Flavonoids work very well together with vitamin C, especially the citrus flavonoids improve its absorption into the body. The intake of polyphenols is generally considered safe, side effects are usually not known. The exception is catechin, which can possibly cause fever and anemia, although these side effects disappear after discontinuation. If polyphenols are to be taken for diseases, the treating therapist should be consulted for advice. This is also the best way to check for possible interactions with other medications.