Natural Relief for Allergies and Asthma
Jennifer Mueller, M.S. Candidate
Summer is here, and with it, hundreds of
flowering plants releasing clouds of pollen into the air. For anyone
with allergies, this is the worst time of year. Medications are
available, but they either put you in a daze, or are extremely
expensive. Allergy sufferers wonder: isn't there anything that will
help? The answer is a resounding yes although the source may not be what
The next time you browse through the produce department in your local
supermarket, take a closer look at some of those fruits and vegetables.
They contain substances called bioflavonoids, which are part of a larger
group of molecules called polyphenols. These flavonoids play a major
role in the color and taste of many of the fruits and vegetables we eat,
and they possess numerous medical benefits as well.
Interest in the biological function of flavonoids was first expressed in
1936 by Szent-Gyorgi, et al, who reported that flavonoids alleviated
some of the symptoms of scurvy.(1) At this time, these compounds were
designated as vitamin P. However, further studies in the next few
decades showed conflicting and inconclusive results when compared to
Szent-Gyorgis research. Consequently, interest died until only recently.
Within the last few decades, extensive studies have been conducted on a
wide range of flavonoids, finding a variety of beneficial effects.
Anthocyanidins (found in red wine and pomegranates) have demonstrated
anti-cancer, anti-inflammatory, and anti-microbial effects.(2,3)
Gallates and catechins (found in green teas) have shown anti-cancer
effects as well.(4) Quercetin, rutin and others have shown strong
protective effects against lipid peroxidation,(2) and quercetin has also
been proven effective in the prevention and treatment of
diabetes-induced cataracts.(5) Silymarin (found in milk thistle) is used
in Europe as a prescription drug to treat various liver diseases, and
cyanadin and catechins have also shown similar hepatoprotective
effects.(2,3) Numerous flavonoids have demonstrated potent
anti-microbial and anti-viral effects, and some, such as quercetin and
morin, were effective in lowering cholesterol in the blood.(6) While
numerous beneficial effects of flavonoids have been examined, perhaps
one of the best documented medical applications is their anti-allergic
Allergies and Flavonoids
An allergic reaction is caused by a rapid release of histamine from mast
cells (immune cells). Following a stimulus by an allergen whether the
mode of contact is inhalation, touch, or ingestion the enzyme calcium
ATP-ase is activated. This pumps calcium into the cells, stimulating the
release of histamine, which travels throughout the body and starts the
chain of events which eventually leads to the familiar symptoms of
allergy: nasal discharge, stinging and watery eyes, itching, and hives.
There are numerous medications available, both by prescription and over
the counter, to give relief to the allergy sufferer. However, most, if
not all, produce unpleasant side effects such as dry mouth, nausea, and
drowsiness.(7) These medications work by blocking the histamine
receptors on other cells, not by blocking the initial release of the
histamine itself. Asthma is caused by a
similar pathway to allergy. The asthma trigger stimulates the immune
cells to induce the production of prostaglandins and leukotrienes and
the release of histamines. However, in asthma, the ratio of leukotrienes
to prostaglandins is more important in the progression of the symptoms
than the release of histamine.(9)
Bioflavonoids have long been known to possess anti-allergic effects. As
early as the 1950s, studies showed that flavonoids could prevent the
release of histamines and inhibit anaphylaxis.(8) It wasnt until some
years later, however, that any more attention was paid to the link
between flavonoids and allergy. The breakthrough was the discovery of
the flavonoid khellin that turned out to be an effective muscle
relaxant. During attempts to improve its muscle-relaxing capabilities, a
series of derivatives was synthesized. One of these derivatives was
disodium cromoglycate, Cromolyn. Studies suggest that Cromolyn could
alleviate the symptoms of asthma and reduce the need for other asthma
medications when taken over long periods of time. It acts by decreasing
the transport of calcium into the cells, thus slowing the release of
histamine.(10) Preliminary studies suggest that Cromolyn is effective in
reducing the symptoms of allergy, both when taken via inhalation and
when applied topically in the eyes.(10)
Other derivatives of khellin have also been shown to be effective
against asthma and allergy. The experimental bioflavonoid-derivative
drugs FPL 52757 and FPL 57787 were given orally to rats who were then
exposed to an allergen. Both substances showed protection (similar to
that seen with Cromolyn) against symptoms to the chemically-induced
allergic reaction.(11) FPL 55712 given via aerosol reduced asthmatic
symptoms in guinea pigs,(12) and FPL 52694 given orally to rats
inhibited reactions to allergens injected under the skin. The mode of
action for all these experimental bioflavonoid derivatives appears
similar to Cromolyn inhibition of histamine release.(13)
Natural vs. Synthetic
While Cromolyn and the FPL series are all synthetically derived
compounds, natural flavonoids have also shown anti-allergy and
anti-asthmatic activity. One of the earliest studies examined varying
levels of the bioflavonoid rutin combined with an antihistamine drug, in
human subjects. Seventy-five percent of the subjects reported greater
relief from allergy symptoms (sneezing, itching and tearing of eyes)
when given the combination of flavonoid and drug than when given the
drug alone.(7) In a later study, baicalin (a flavonoid used in ancient
Chinese medicine to treat allergy and inflammation) was given orally to
guinea pigs. After flavonoid treatment, asthma was chemically induced.
The animals pretreated with the flavonoid showed a greater suppression
of symptoms (histamine release and bronchoconstriction) than those that
In vitro studies (done in cell cultures instead of whole animals) have
been conducted to determine the exact mode of action by which flavonoids
suppress the symptoms of allergy and asthma. As mentioned earlier, the
symptoms are caused by the release of
histamine, leukotrienes, and prostaglandins from the immune cells. In
one study, mast cells were treated with eleven different flavonoids,
including quercetin and catechins. Histamine release was chemically
induced. All the flavonoids tested exhibited some level of protective
effect against the release of histamine by preventing the uptake of
calcium into the cells.(15) Similar results have been shown in basophils
treated with quercetin, which is chemically similar to the synthetically
derived Cromolyn. Quercetin was quite effective at inhibiting the
release of histamine from these cells, even at low doses.(16) It is
interesting to note that in these and other studies, quercetin has been
proven more effective at blocking histamine release than the
synthetically derived Cromolyn.(4) While the exact mechanism by which
flavonoids prevent calcium influx into the cells is still debated, it is
thought that flavonoids may inhibit the enzyme cyclic AMP
phosphodiesterase. This results in raised levels of cyclic AMP inside
the mast cells, preventing the release of the histamine.(17,18)
Flavonoids exert their protective effects in other ways as well. They
inhibit lipoxygenase--the compound which stimulates the biosynthesis of
leukotrienes, which play an important role in hypersensitivity to
allergens, as well as www.ion of asthmatic symptoms.(18,19) Certain
flavonoids also inhibit arachidonic acid peroxidation as well.
Arachidonic acid is a precursor of prostaglandins, compounds involved in
inflammation and allergic responses. Catechins were some of the most
potent inhibitors of prostaglandin synthesis.(19)
As can be seen, bioflavonoids are highly effective anti-allergy and
anti-asthma agents. While more research is needed to determine exact
doses, the best methods of delivery (oral versus inhaled), and which
combinations of flavonoids can offer the best effects, it is clear that
bioflavonoids offer allergy sufferers a new form of relief, without the
annoying side effects of prescription drugs. When taking into account
all the other ways they can act as anti-inflammatories, anti-viral and
anti-microbial agents, and even anti-cancer agents, it is clear that
bioflavonoids offer a wide range of possibilities for the future of
Jennifer Mueller is a Masters Candidate in Nutrition Science at the
University of California at Davis. Her primary focus is developmental
nutrition and prenatal health. She was Managing Editor for the Journal
of Optimal Nutrition and has studied under Dr. Brian Liebovitz, the
noted medical nutritionist.
source of nutrients and supplements.
did we qualify them ?
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