Analysis by Dr. Joseph Mercola Fact Checked August 22, 2022
PDF: https://media.mercola.com/ImageServer/Public/2022/August/PDF/quercetin-antitumor-effects-pdf.pdf
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Quercetin has an apoptotic effect on aging cells
that may help prevent or be helpful in the treatment of cancer; years of
research have also demonstrated it prevents chemically induced cancer and lung
cancer, and inhibits the proliferation of cancer cells
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Quercetin has also demonstrated the ability to
mitigate some of the effects of sleep deprivation, including mood changes,
anxiety, memory performance, hyperactivity and cognitive impairment
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The combination of quercetin, bromelain, vitamin C
and zinc has emerged in at least two of the successful protocols used to treat
COVID-19; historically, data have shown it is effective against influenza,
zika, hepatitis B and rhinovirus responsible for the common cold
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Quercetin is not water-soluble and is poorly
absorbed unless it is paired with bromelain or vitamin C. Quercetin has shown
positive benefits for heart disease, high blood pressure, metabolic syndrome,
NAFLD and arthritis
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Quercetin is found in onions, red grapes and green
tea. It could be a useful supplement to stock in your medicine chest to use
when you believe you may be getting an upper respiratory infection
Quercetin is an
antioxidant flavonol that's found in foods such as red grapes, green tea,
elderflower and onions, to name a few.1 As the health
benefits of the supplement become more widely known, the market has grown
rapidly.2 According to market
research, quercetin market was worth $261.12 million in 2020 and is expected to
reach $406.58 million in 2027.
Quercetin has a
wide range of benefits, which has made it useful for a variety of different
health conditions. In the last two years, the antiviral benefits of quercetin
have been the focus of many studies.3 However, there are
other, lesser-known benefits, including the effects as a senolytic agent
against senescence-mediated cancer growth.4
It is perhaps
most well-known as a strong antioxidant5 and antiviral.6 For example,
Elderflower extract, which is rich in quercetin, is a traditional tonic used to
boost immunity. In supplement form, quercetin has been used to prevent and
treat the common cold and influenza.7
According to
Mount Sinai,8 quercetin
should be used with caution as it may interact with certain antibiotics by
reducing the effectiveness of the drug. It may also enhance the effect of some
blood thinners, which can increase your risk of bleeding. In addition to these,
it may interact with corticosteroids, digoxin, cyclosporine and
fluoroquinolones.
Quercetin Effect on
Senescence-Mediated Cancer Cells
A paper9 published in August
2022 in Nutrition Research analyzed the pro-apoptotic effect that quercetin has
on aging cells. The paper reviewed preclinical and early phase data using
quercetin as a senolytic agent and found the data showed it was effective in
“preventing or alleviating cancer formation.”
The authors
reviewed the importance of cellular aging in the development of cancer cells
and the effect that quercetin may have on the suppression of cancer cell
proliferation. Research has found that cellular aging can suppress tumor
development, but paradoxically can also enhance cancer development.10
Cellular
senescence is a dynamic and multi-step process that is associated with
alterations in metabolic activity and gene expression.11 This can compromise
tissue regeneration and contribute to aging. On the other hand, by removing
senescent cells, age-related dysfunction can be attenuated and potentially
extend the lifespan.
One paper12 published in 2008
recognized that animal studies had demonstrated quercetin could prevent
chemically-induced cancer growth and epidemiological studies found it was
associated with preventing lung cancer. One study13 focused on the effect
that physiologically attainable doses of quercetin had on the inhibition of
cancer cell proliferation. The researchers believed their study demonstrated
quercetin had chemopreventive properties.
Lab studies14 have also
demonstrated that quercetin is a strong antioxidant and has pro-apoptotic
effects on tumor cells, with the ability to block growth at different phases of
the cell cycle. Research15 also has demonstrated that quercetin can
promote the loss of cell viability and autophagy through several pathways,
including those involving mitochondrial function and glucose metabolism.
Data16 indicate that
quercetin could play a role in cancer treatment as it reportedly has
synergistic effects in combination with chemotherapy agents or radiation
therapy. Quercetin has also shown promising results with chemoprotective and
radioprotective properties, by protecting normal cells against the effects of
chemotherapy and radiation therapy.
One paper17 identified some of
the anti-inflammatory, antioxidant and antiproliferative properties quercetin
has that enhances breast cancer treatment, while another18 evaluated its effect
on the treatment of ovarian cancer, which is a serious cancer growth and threat
to women's health.
Flavonoid May Attenuate Behavior
From Sleep Deprivation
The strength of
the antioxidant properties of quercetin is likely one factor in the ability to
improve mood-related behaviors in animal studies where the subjects underwent
sleep deprivation. A study19 published in 2022 used a sleep deprivation
model using 30 male albino mice. The mice were split into five groups.
The
intervention groups received either astaxanthin or one of two doses of
quercetin. Their activities were monitored, and brain samples were later
collected. Researchers found that during persistent wakefulness, the animals
experienced anxiety and depression-like behavior. In the sleep-deprived group,
brain samples showed an enhancement in prooxidants.
In the group
pretreated with quercetin, these behaviors were reversed. The researchers found
that quercetin could reduce anxiety caused by sleep deprivation in the animals.20 The structure of this
study was similar to another21 published in 2021 in which the researchers
split the animals into five groups that received the same intervention and
sleep deprivation just described.
The researchers
hypothesized, and the data showed, that quercetin ameliorated the effects of
sleep deprivation on memory performance, depression-like behavior and against
the loss of prefrontal cortex neurons. Researchers have been interested in how
the powerful antioxidant effects of quercetin might mitigate the damage and
impairment commonly found following sleep disruption.
In one study22 published in 2016,
the researchers hypothesized that quercetin could reduce the manic-like
behavior induced by 24 hours of paradoxical sleep deprivation in mice.
Paradoxical sleep is another name given to rapid eye movement (REM) sleep, the
deprivation of which has led to chronic conditions such as obesity and stress
disorders in people.23
In the animal
study,24 the researchers found
that quercetin blocked hyperactivity that was induced by sleep deprivation. In
another study,25 researchers hypothesized that the deficits in the hippocampal area
associated with sleep deprivation could be ameliorated with a preparation of
grape seed polyphenol extract, concord grape juice and resveratrol.
They found the
preparation improved sleep deprivation-induced memory deficits and quercetin,
found in grape seed extract and grape juice, was an important factor in
attenuating cognitive impairment caused by acute sleep deprivation.
Quadruple Therapy Effective
on SARS-CoV-2
Quercetin has
been studied for its antiviral effect and has proven to show inhibition in the
early stages of a flu infection26 and is a promising agent against Epstein Barr
Virus,27 Zika virus,28 Hepatitis B29 and rhinovirus30 responsible for the
common cold.
It was only
logical then, as the COVID-19 pandemic emerged, that researchers would
investigate the efficacy of quercetin against the SARS-CoV-2 virus. In the
early months of the declared pandemic, a review31 was published that
found the administration of bromelain, quercetin, vitamin C and zinc “showed
promising results in improving clinical outcomes among COVID-19 patients.”32
In this paper,
the researchers identified the antioxidant’s ability to inhibit proinflammatory
cytokines and to clinically block human mast cell cytokine release as an
important property in the fight against severe COVID-19 disease, which is
associated with increased levels of cytokine production. They also identified
the independent actions that bromelain has in activating a healthy immune
system.
However,
bromelain and vitamin C play another role in the administration of quercetin.
Because quercetin is generally not soluble in water, it can be poorly absorbed.
When administered with bromelain or vitamin C, it increases the absorption and
bioavailability of the antioxidant.33
Bromelain is a
proteolytic enzyme found in the stem of the pineapple plant.34 Independently, it has
been used as a supplement to help reduce swelling after surgery or injury, or
in the nose and sinuses. It is also applied topically to help treat burns.
The combination
of quercetin with bromelain or vitamin C has also been a part of several
successful protocols used to treat COVID-19.35,36 Quercetin is a zinc
ionophore,37 which helps improve
the cell’s ability to absorb zinc where it is effective as an antiviral.38
Dr. Vladimir
Zelenko was among the first physicians to discover and implement a treatment
that has been credited with saving millions of lives around the world.39 His early protocol
used hydroxychloroquine,40 another zinc ionophore. However, as research
data showed that quercetin was as effective as hydroxychloroquine, his early
treatment options for low-risk patients included quercetin with vitamin C and
zinc.41
Sadly, Dr.
Zelenko passed away on June 30, 2022, at the age of 48 after a long battle with
cancer. While treating patients, he oversaw the treatment of roughly 7,500
people using his protocol, during which time only three patients died.42
More Benefits of Quercetin
and Bromelain
The antioxidant
and anti-inflammatory43 health benefits of quercetin likely
contribute to the other lesser-known benefits of this supplement. The
anti-inflammatory effects of quercetin are crucial since inflammation is at the
root of many diseases, including autoimmune disorders, heart disease and
cancer.
One review of
the literature44 found quercetin is “a strong anti-inflammatory weapon” that may be
used in the fight against inflammatory diseases, such as obesity and Type 2
diabetes. Another revealed45 that supplementation could reduce systolic
blood pressure, and a third animal study46 demonstrated that
supplementation with quercetin and exercise could reduce atherosclerotic plaque
formation.
Quercetin has also shown
promise in relieving the symptoms of allergies. It works by inhibiting histamine
release and decreasing proinflammatory cytokine production and leukotrienes
creation.47 The combination of
quercetin and bromelain or vitamin C has also been promoted to help improve
athletic performance based on the antioxidant potential of both flavonoids.48,49,50 Quercetin has also
been studied for the positive health benefits it has on:
High blood pressure51 |
Cardiovascular disease52,53 |
Metabolic syndrome54 |
Certain kinds of cancer55 |
Nonalcoholic fatty liver
disease (NAFLD)56 |
Mood disorders57 |
Gout58 |
Arthritis59 |
Quercetin From Food and Supplements
Considering the
wide-ranging benefits that quercetin has on human health, it could be a useful
supplement for many, whether it is used acutely or long-term. It is one of the
supplements I recommend keeping in your medicine chest for times when you may
be feeling as if you're getting an upper respiratory infection. If you're prone
to colds and flu, consider taking it for a couple of months before the cold and
flu season hits to support your immune system.
If you feel as
if you have a cold or flu, consider using quercetin with bromelain or vitamin C
in addition to zinc.60 Over-the-counter zinc lozenges make it easy
to consume zinc for the short time it’s needed when you’re feeling ill. Be sure
to eat before taking zinc as it can make you nauseous.
On a long-term
basis, it has been useful for those with metabolic syndrome. However, it is
much better to address fundamental strategies for dealing with metabolic
syndrome, such as diet and exercise, and use a supplement only as an adjunctive
therapy. If you have one or more conditions that make up metabolic syndrome,
you would be wise to limit your total sugar intake to 15 grams per day.
For comparison,
the American Heart Association61 reports that the average adult consumes 77
grams of sugar each day, which is more than three times the recommended amount
for women. The number for children is even worse, with the average American
child consuming 81 grams of sugar per day. Sugar-laden beverages are the
leading source of added sugars in the diet.
Quercetin can function in
several pathways to help reduce your risk of cancer. In addition to reducing
the inflammatory response in your body and thus your risk of obesity and
obesity-related cancer,62 it also promotes apoptosis at the cellular
level to prevent cancer.63 When combined with exercise and reduced sugar
consumption, you are making strong steps toward taking control of your health.
Sources and References
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1 Superfoodly, 100 Quercetin Foods
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2 Brand Essence Research, December 2021
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3, 31, 32 Research
International Journal of Endocrinology and Diabetes, 2020; 1(1)
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4, 9, 63 Nutrition Research, 2022; 104
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6, 7 Viruses 2016; 8(1):6
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8 Mount Sinai, Quercetin, Possible
Interactions
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10 Critical Reviews in Oncology
and Hematology, 2011;79(2)
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11 Frontiers in
Cell and Developmental Biology, 2021; doi.org/10.3389/fcell.2021.645593
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12 Cancer Letters, 2008;269(2)
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13 Journal of Cellular Biochemistry, 2009; 106 (1)
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14 Evidence-Based Complementary
and Alternative Medicine, 2011; doi.org/10.1093/ecam/neq053
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15 International Journal of Molecular Sciences, 2019; 20(13)
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16 Current Medicinal Chemistry, 2015;
22(26)
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17 Life Sciences, 2020;248(117463)
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18 Cell and Bioscience, 2020; 10(32)
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19, 20 Nigerian
Journal of Experimental and Clinical Biosciences, 2022; 10(1)
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21 Biosciences, Biotechnology Research
Asia, 2021, 18(4)
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22, 24 Free Radical
Biology in Medicine, 2016;99
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23 Sleep Foundation, Mark 25, 2022
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25 Neurochemistry International, 2015; 89
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26 Viruses, 2016; 8(1)
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28 Virologica Sinica, 2017;32
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29 Virologica Sinica, 2015; 30
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30 Antiviral Research, 2012;94(3)
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34 National Center for
Complementary and Integrative Health, Bromelain
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35, 41 Vladamir Zelenko, COVID-19 Treatment Protocol
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36 FLCCC
Alliance, ICare: Early COVID Treatment
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37 Journal of Agricultural and
Food Chemistry, 2014;62(32)
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38 Advances in Nutrition, 2019;10(4)
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39 America’s Frontline News, July 1,
2022
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42 America’s
Frontline News, July 1, 2022, para 6
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43 Journal of Research and Medical
Sciences, 2012; 17(7)
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44 Mediators of Inflammation, 2016; 2016
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45 International Journal of
Preventive Medicine, 2013; 4(7)
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46 Journal of the international
Society of Sports Nutrition, 2014; 11
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48 International Journal of
Preventive Medicine, 2013;4(1)
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49 International Journal of
Preventive Medicine, 2013;4(Suppl 1)
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50 Journal of Research in Medical
Sciences, 2012;17(4)
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51 Journal of the American Heart
Association 2016;5(7)
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52 International Journal of
Molecular Science 2019;20(23)
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53 European Journal of Medicine, 2018;155
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54 Phytotherapy Research 2019; 33(5)
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55 Scientific Reports 2016; 6(24049)
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56 Phytotherapy Research 2019;
doi.org/10.1002/ptr.6486
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57 Fitoterapia 2015;106 7 lines up
from bottom abstract
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58 British Journal of Nutrition, 2016;115(5)
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59 Journal of the American College
of Nutrition, 2017;36(1)
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60 Journal of Family Practice, 2011;60(11)
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61 American
Heart Association, How Much Sugar is Too Much?
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62 National
Cancer Institute, Obesity and Cancer