Description
What are flavonoids?
Flavonoids, an amazing array of over
6,000 different substances found in virtually all plants, are responsible for
many of the plant colors that dazzle us with their brilliant shades of yellow,
orange, and red.
Classified as plant pigments,
flavonoids were discovered in 1938 when a Hungarian scientist named Albert
Szent-Gyorgyi used the term "vitamin P" to describe them.
The chemistry of flavonoids is
complicated, and within the non-technical term "flavonoids" can be
found many different chemical groups of substances. These groups include
flavonols, dihydroflavonols, flavones, isoflavones, flavanones, anthocyanins,
and anthocyanidins. Within each of these groups fall hundreds, and sometimes
thousands of different flavonoids.
For example, well-known flavonols
include quercetin, rutin, and hesperidin, while well-known flavones include
apigenin and luteolin. Flavonoids may also be named directly after the unique
plant that contains them. Ginkgetin is a flavonoid from the ginkgo tree, and
tangeretin is a flavonoid from the tangerine.
What is are the
functions of flavonoids?
Protection of cell
structures
Most flavonoids function in the human
body as antioxidants. In this capacity, they help neutralize overly reactive
oxygen-containing molecules and prevent these overly reactive molecules from
damaging parts of cells. Particularly in oriental medicine, plant flavonoids
have been used for centuries in conjunction with their antioxidant, protective
properties. Scultellaria root, cornus fruit, licorice, and green tea are
examples of flavonoid-containing foods widely used in oriental medicine. While
flavonoids may exert their cell structure protection through a variety of
mechanisms, one of their potent effects may be through their ability to
increase levels of glutathione, a powerful antioxidant, as suggested by various
research studies.
Vitamin C support
The relationship between flavonoids and
vitamin C was actually discovered by mistake. Dr. Albert Szent-Gyorgyi, the
Nobel Prize winning researcher who discovered flavonoids, was attempting to
make a preparation of vitamin
C
for one of his patients with blood vessel problems. The preparation he gave the
patient was not 100% pure--it contained other substances along with the vitamin
C. It worked amazingly well.
Later, when Dr. Szent-Gyorgyi purchased
a pure solution of vitamin C, he found it was not nearly so effective with his
patient. He suspected flavonoids as the magic addition to vitamin C in his
first impure preparation. Present-day research has clearly documented the
synergistic (mutually beneficial) relationship between flavonoids and vitamin
C. Each substance improves the antioxidant activity of the other, and many of
the vitamin-related functions of vitamin C also appear to require the presence
of flavonoids.
Inflammation control
Inflammation--the body's natural
response to danger or damage--must always be carefully regulated to prevent
overactivation of the immune system and unwanted immune response. Many types of
cells involved with the immune system--including T cells, B cells, NK cells,
mast cells, and neutrophils--have been shown to alter their behavior in the
presence of flavonoids. Prevention of excessive inflammation appear to be a key
role played by many different chemical categories of flavonoids.
Antibiotic activity
In some cases, flavonoids can act
directly as antibiotics by disrupting the function of microorganisms like
viruses or bacteria. The antiviral function of flavonoids has been demonstrated
with the HIV virus, and also with HSV-1, a herpes simplex virus.
What are deficiency
symptoms for flavonoids?
Excessive bruisability, nose bleeds,
swelling after injury, and hemorrhoids can be indicators of flavonoid
deficiency. Generally weakened immune function, as evidenced by frequent colds
or infections, can also be a sign of inadequate dietary intake of flavonoids.
Toxicity Symptoms
What are toxicity
symptoms for flavonoids?
Even in very high amounts (for example,
140 grams per day), flavonoids do not appear to cause unwanted side effects.
Even when raised to the level of 10% of total caloric intake, flavonoid
supplementation has been shown non-toxic. Studies during pregnancy have also
failed to show problems with high-level intake of flavonoids.
How do cooking,
storage, or processing affect flavonoids?
Heat, degree of acidity (pH), and
degree of processing can have a dramatic impact on the flavonoid content of
food. For example, in fresh cut spinach, boiling extracts
50% of the total flavonoid content.
With onions (a less delicate
food), boiling still removes about 30% of the flavonoids (and specifically, a
group of flavonoids called the quercitin glycosides). Overcooking of vegetables
has particularly problematic effects on this category of nutrients.
What factors might
contribute to a deficiency of flavonoids?
Poor intake of fruits and
vegetables--or routine intake of high-processed fruits and vegetables--are
common contributing factors to flavonoid deficiency. It is difficult to
overemphasize the impact of processing and a non-whole foods diet on flavonoid
intake. If the pulpy, fibrous parts of fruits are eliminated from the juice, and
the vibrant natural colors of canned vegetables are lost during repeated
heating, risk of flavonoid deficiency is greatly increased.
How do other
nutrients interact with flavonoids?
Present-day research has clearly
documented the synergistic (mutually beneficial) relationship between
flavonoids and vitamin
C.
Each substance improves the antioxidant activity of the other, and many of the
vitamin-related functions of vitamin C also appear to require the presence of
flavonoids.
Health Conditions
What health
conditions require special emphasis on flavonoids?
Flavonoids may play a role in the prevention and/or treatment of the
following health conditions:
- Allergy
- Asthma
- Atopic
dermatitis
- Candida
infection
- Cataracts
- Diabetes
- Gout
- Hemorrhoids
- Macular
degeneration
- Migraine
- Periodontal
disease
- Stomach
ulcer
- Varicose
veins
What foods provide
flavonoids?
Virtually all fruits, vegetables, herbs
and spices contain flavonoids. They are also found in other types of food,
including dry beans (where they give red beans,black
beans,
and speckled beans their color) and grains (where the color provided by
flavonoids is usually in the yellow family). Products made from the foods above
(for example, wines made from grapes) also typically
contain a wide variety of flavonoids.
While the flavonoid family is too
complex to report all of its food connections, some highlights are especially
important. In the fruit family, it is berries that come out highest in the
chemical category of flavonoids called anthocyanins. Black raspberries, for example, may
contain up to 100 milligrams of anthocyanins per ounce.
Green tea has
flavonoid components called catechins that may reach 1,000 milligrams (or 1
gram) per cup. In general the more colorful components of the food--like the
skins of fruits--contain the highest concentration of flavonoids. An exception
to this rule, however, is the white pulpy inside of oranges. Unlike the watery
orange-colored sections of this fruit, which contain virtually all of its
vitamin C, the orange's flavonoids are found in the white pulpy portion inside
the skin and surrounding the sections
What Does A
Tea Leaf Contain? - Fresh-cut
tealeaves consist of 75-80% water. A variety of green tea flavors are formed
through the combination of three main taste components:
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Catechin– Bitterness & Astringency
Caffeine– Bitterness
Theanine & Amino Acids–
Flavor & Sweetness
In this section you'll learn what's in a tea leaf, and about the effect of
these specific ingredients in green tea: Catechin, Caffeine, the Amino Acids Theanine & Butyric Acid, Vitamins A, B1, B2, B3, C, E, F, K, P, & U, Chlorophyll, Minerals, Pectin, Saccharides, Saponin and a handy comparison of ingredients in green teas.
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Catechin - Catechin is a tannin peculiar to
green tea because the black tea fermentation process reduces catechins in
black tea. Catechin is a powerful, water soluable polyphenol and antioxidant
that is easily oxidized.
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Several
thousand types are available in the plant world. As many as two thousand are
known to have a flavon structure and are called flavonoids. Catechin is one of
them.
Research aimed at finding the active compounds in green tea revealed that its
protective effects are due chiefly to catechins. Tea contains four main
catechin substances: EC, ECg, EGC and EGCg, all of which are inclusively called
catechin. Epigallocatechin gallate (EGCG) is the most powerful of these
catechins. EGCG as an antioxidant is about 25-100 times more potent than
vitamins C and E. One cup of green tea
provides 10-40 mg of polyphenols and has antioxidant effects greater than a
serving of broccoli, spinach, carrots, or strawberries. The high
antioxidant activity of green tea makes it beneficial for protecting the body
from oxidative damage due to free radicals. Research shows that green tea may
help the arterial wall by reducing lipids. Green tea can protect against
experimentally induced DNA damage, and slow or halt the initiation and progression
of undesirable cell colonies. Studies show evidence that green tea provides
immunoprotective qualities, particularly in the case of patients undergoing
radiation or chemotherapy. White blood cell count appear to be maintained more
effectively in patients consuming green tea compared to non-supplemented
patients.
Green
tea is manufactured from fresh, unfermented tea leaves; the oxidation of
catechins is minimal, and hence they are able to serve as antioxidants.
Researchers believe that catechin is effective because it easily sticks to
proteins, blocking bacteria from adhering to cell walls and disrupting their
ability to destroy them. Viruses have ‘hooks’ on their surfaces and can attach
to cell walls. The catechin in green tea prevents viruses from adhering and
causing harm. Catechin reacts with toxins created by harmful bacteria (many of
which belong to the protein family) and harmful metals such as lead, mercury,
chrome, and cadmium.
Tannin in green tea is mostly catechin and is a key component in its taste
providing the astringency. The amount of catechin tends to increase as the
season progresses. Spring tea (first crop) contains 12-13% catechin (13-17% as
tannin) while summer tea (third crop) contains 13-14% (17-21% as tannin). If leaf order is compared, younger leaves
include more catechin than mature ones. First leaves contain 14%, second 13%, third 12%, and fourth 12%.
This explains why second and third crop summer teas are more astringent while Bancha is less so. Gyokuro green tea, whose leaves are
covered during growth, contains less catechin and astringency (10% as tannin)
because it gets less sunshine then Sencha
