Black Tea Compounds Show
Research Further Demonstrate How Naturally-Occurring
Antioxidants, Carotenoids, Phytochemicals From Teas and
Plant Extracts Affect The Immune system
Theaflavins are beneficail natural compounds found in black tea
and may reduce allergic response in people with sensitive skin and
related conditions, suggests a new study. In the laboratory, subjects
fed extracts from black tea were found to produce fewer inflammatory
compounds on exposure to an allergen, while antioxidant levels in
the blood were also maintained by the tea compounds. The findings
are published in the Journal of the Science of Food and Agriculture.
Interest in tea and its constituents has bloomed in recent years,
with the greatest focus on the leaf’s polyphenol content. Green tea
contains between 30 and 40 per cent of water-extractable
polyphenols, while black tea (green tea that has been oxidized by
fermentation) contains between 3 and 10 per cent. Oolong tea is
semi-fermented tea and is somewhere between green and black tea.
The four primary polyphenols found in fresh tealeaves are
epigallocatechin gallate (EGCG), epigallocatechin (EGC),
epicatechin gallate (ECG), and epicatechin (EC).
Most of the studies have focussed on green tea and its constituents,
most notably EGCG. The new study looked at theaflavins from black
tea in a mouse model of type IV allergy. Unlike many other types of
allergy, the type (type IV) tested in this new study directly involves
the immune system’s T-cells and not the participation of antibodies.
According to background information in the article, type IV allergy
is known as delayed type hypersensitivity, with appearance of the
allergic response occurring 12 to 24 hours after exposure. Contact
dermatitis is an example of type IV allergy.
Exposure to the allergen is said to trigger the release of
pro-inflammatory cytokines by type 1 T helper (Th1) cells. Such
increases were prevented when sensitised laboratory subjects
were fed various theaflavins from black tea, according to the new
Researchers from Japan’s Numazu National College of Technology
and Nagoya Women’s University examined the effects of two black
tea theaflavinL: theaflavin-3-gallate and theaflavin-3,3-digallate
(TFDG) on type IV allergy in the laboratory subjects.
When the theaflavins were injected into the skin of the ear, the
researchers noted “significant preventive effects against type IV
allergy”. Furthermore, when administration orally at a level of 50 mg per kg of body weight, similar preventive effects were observed, said the
researchers. Control subjects not fed the black tea compounds
experienced with increases of proinflammatory cytokines like
interleukin-12 (IL-12), tumour necrosis factor-alpha (TNF-alpha),
and interferon-gamma (IFN-gamma). When subjects were fed the
theaflavins, however, the increases were not observed, added the
“The anti-allergic mechanisms of action of theaflavins involve
inhibition of the fluctuations of cytokines and maintenance of
antioxidant status in allergic subjects,” wrote the researchers.
The black tea theaflavins were supplied by Unilever Japan.
Source: Journal of the Science of Food and Agriculture
Published online: “Preventive effects of black tea theaflavins
against mouse type IV allergy”