Quercetin
What is Quercetin?
Quercetin is a plant chemical known as a polyphenolic flavonoid. It is yellow in color. Flavonoids give fruits and vegetables their pigment and act as antioxidants in our bodies.
Quercetin is a powerful anti-inflammatory and thus may be beneficial for conditions associated with inflammatory pain like arthritis. Inflammation in the gastrointestinal tract and the central nervous system is a hallmark of autism so quercetin may have an important role to play in helping to manage this inflammation and mitigate the related symptoms.
Oxidative stress and inflammation are one of the main causes of mitochondrial dysfunction, a common condition among those with autism.
Quercetin’s antioxidant and anti-inflammatory work may help to alleviate mitochondrial dysfunction and the associated symptoms. [26, 27]
Quercetin helps stabilize mast cells in the body, the cells that release histamine. [4] This shows the potential in benefit of quercetin on allergies and allergic diseases, such as allergic asthma, allergic rhinitis (AR), and atopic dermatitis (AD) / eczema.[28, 29]
There is evidence to suggest that quercetin may protect the heart from damage, reduce high blood pressure and prevent cancer. [1-3]
It is estimated that on average people consume anywhere from 3-40mg of quercetin per day from the diet. [7]
Quercetin content in food is reduced with heat and cooking.[8]
Quercetin is considered to be safe and well-tolerated in supplement form but safety studies with high doses (over 1000mg) are lacking. [9]
Interestingly, quercetin has also shown potential as an antimicrobial/antiviral agent, specifically against influenza virus, the common cold, and even COVID-19. [10-13]
Food Sources of Quercetin
Brightly colored fruits and vegetables are good sources of quercetin including [5,6]:
Cherries
Onions
Asparagus
Red leaf lettuce
Apples
Spinach
Chili peppers
Cranberries
Herbs like dill and oregano
Tea and red wine
Supplementation
Quercetin is best absorbed in the chemical forms found in food and when eaten with a meal containing fat. [9]
Examples of common Quercetin supplements include:
Capsule/Softgel
Powder
Note: All supplements are linked to Amazon for convenience, however, buying supplements on Amazon does not guarantee quality, as there are many “unverified resellers” selling nutrition supplements. To buy supplements that are verified to be sent directly to the consumer, you can create an account on the Autism Dietitian FullScript and search for the respective supplement under “Catalog”.
DISCLAIMER: Before starting any supplement or medication, always consult with your healthcare provider to ensure it is a good fit for your child. Dosage can vary based on age, weight, gender, and current diet.
Quercetin & Autism in the Research
Quercetin and ASD
The use of flavonoids such as quercetin has emerged as a promising alternative for therapy against oxidative stress in pediatric neurological diseases. Quercetin can improve central nervous system tumors, ASD, and ADHD progression conditions due to its antioxidant properties. In addition, quercetin therapy may be required to be administered early in chronic insidious pediatric neurological diseases so as to achieve an appreciable clinical benefit in a timely manner. [14]
The dietary supplement, NeuroProtek, was developed with a unique mixture of luteolin with the related flavonoids quercetin and rutin in a liposomal formulation of olive kernel oil, which increases their absorption. Among 37 children with ASD, ages 4-14 years, GI and allergy symptoms improved in about 75 percent of children, eye contact and attention in 50 percent, social interaction in 25 percent and resumption of speech in about 10 percent. There were no adverse effects.[15]
In a pilot study with 50 children, the combination of the flavonoids luteolin and quercetin seemed to be effective in reducing ASD symptoms, with no major adverse effects. [16]
Quercetin and Oxidative Stress
The neuroprotective effects of quercetin against oxidative stress can also be applied in the management of several neurodegenerative disorders with effects such as anti-cancer, anti-inflammatory, anti-viral, anti-obesity and anti-microbial. [14]
Several studies in experimental animals and in humans, have provided supportive evidence for neuroprotective effects of quercetin, either against neurotoxic chemicals or in various models of neuronal injury and neurodegenerative diseases. In addition to a possible direct antioxidant effect, quercetin may also act by stimulating cellular defenses against oxidative stress. [22]
Quercetin may act as an effective intervention against BPA-induced neurotoxicity in zebrafish through down-regulation of oxidative stress. [24]
This study showed that cadmium accumulated in rat testes, leads to oxidative stress and autophagy/cell death. Quercetin can reduce cadmium toxicity by reducing oxidative stress and inhibiting autophagy. [25]
Quercetin and Gastrointestinal Health
Quercetin may be useful in the prevention and/or treatment of nonsteroidal anti-inflammatory drug-associated side effects, such as gastrointestinal oxidative stress and inflammation, without interfering with their therapeutic efficacy. [17]
This study provides the first strong evidence that quercetin can be considered an important candidate for improving chronic constipation induced by loperamide treatment in animal models. [18]
A laxative effect on stool-related factors was observed in the constipation model, treated with 20 or 40 mg/kg of quercetin. These results therefore provide novel evidence that various flavonoids can contribute to improving constipation, and are potential candidates for laxative drugs.[18]
Maternal exposure to fine particulate matter may have some certain negative effects on intestinal oxidative stress, inflammation, and tight junctions. Quercetin administration may protect the offspring against these adverse effects. Changes of Bacteroides abundance play an important role in the process.[23]
Quercetin and Mental Health
Repeated treatment with quercetin (25 mg/kg, for 14 days) reversed the behavioral hyperactivity in mice and was able to prevent depressant-like effects, likely due to its antioxidant activity. [19]
Quercetin can improve anxiety-like behaviors caused by chronic neuroinflammation. This anxiolytic effect of quercetin has been shown to be due to its anti-inflammatory effects and thus it has potential as a therapeutic agent to inhibit symptoms in neuropsychiatric diseases, such as anxiety. [20]
Quercetin could prevent the impairment of antioxidant enzymes and also produce antianxiety, antidepressant effect and enhance memory following stress in mice. [21]
Quercetin and Allergic Diseases
While more research needs to be done, one study suggests that quercetin has the potential to reduce the most significant pathologies of asthma such as eosinophil and neutrophil recruitment, the activation of bronchial epithelial cells, collagen and mucus production and airway hyperactivity. [28]
It would be a good candidate as a supplement for the management and treatment of allergic diseases, especially rhinitis. [28]
Quercetin, which has a long story of usage in human history, has been demonstrated sufficient efficacy and has no significant side effects. [28]
Another study suggests that topical administration of quercetin plays a beneficial role in controlling atopic dermatitis (AD) / eczema symptoms in mice, which may serve as potential candidate for AD treatment.
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[3] Reyes-Farias M, Carrasco-Pozo C. The Anti-Cancer Effect of Quercetin: Molecular Implications in Cancer Metabolism. Int J Mol Sci. 2019;20(13):E3177.
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[9] Quercetin. Fullscript.com. https://fullscript.com/ingredient/quercetin. Published May 11, 2021. Accessed December 11, 2021.
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[11] Colunga Biancatelli RML, Berrill M, Catravas JD, Marik PE. Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19). Front Immunol. 2020;11:1451.
[12] Mehrbod P, Hudy D, Shyntum D, Markowski J, Łos MJ, Ghavami S. Quercetin as a Natural Therapeutic Candidate for the Treatment of Influenza Virus. Biomolecules. 2020;11(1):E10.
[13] Kinker B. Quercetin: A promising treatment for the common cold. J anc dis prev remedies. 2014;02(02). doi:10.4172/2329-8731.1000111
[14] Alvarez-Arellano L, Salazar-García M, Corona JC. Neuroprotective Effects of Quercetin in Pediatric Neurological Diseases. Molecules. 2020;25(23):E5597.
[15] Theoharides TC, Asadi S, Panagiotidou S. A case series of a luteolin formulation (NeuroProtek®) in children with autism spectrum disorders. Int J Immunopathol Pharmacol. 2012;25(2):317-23.
[16] Taliou A, Zintzaras E, Lykouras L, Francis K. An open-label pilot study of a formulation containing the anti-inflammatory flavonoid luteolin and its effects on behavior in children with autism spectrum disorders. Clin Ther. 2013;35(5):592-602.
[17] Carrasco-Pozo C, Castillo RL, Beltrán C, Miranda A, Fuentes J, Gotteland M. Molecular mechanisms of gastrointestinal protection by quercetin against indomethacin-induced damage: role of NF-κB and Nrf2. J Nutr Biochem. 2016;27:289-98.
[18] Kim JE, Lee MR, Park JJ, et al. Quercetin promotes gastrointestinal motility and mucin secretion in loperamide-induced constipation of SD rats through regulation of the mAChRs downstream signal. Pharm Biol. 2018;56(1):309-17.
[19] Holzmann I, da Silva LM, Corrêa da Silva JA, Steimbach VM, de Souza MM. Antidepressant-like effect of quercetin in bulbectomized mice and involvement of the antioxidant defenses, and the glutamatergic and oxidonitrergic pathways. Pharmacol Biochem Behav. 2015;136:55-63.
[20] Lee B, Yeom M, Shim I, Lee H, Hahm DH. Protective Effects of Quercetin on Anxiety-Like Symptoms and Neuroinflammation Induced by Lipopolysaccharide in Rats. Evid Based Complement Alternat Med. 2020;2020:4892415.
[21] Samad N, Saleem A, Yasmin F, Shehzad MA. Quercetin protects against stress-induced anxiety- and depression-like behavior and improves memory in male mice. Physiol Res. 2018;67(5):795-808.
[22] Costa LG, Garrick JM, Roquè PJ, Pellacani C. Mechanisms of Neuroprotection by Quercetin: Counteracting Oxidative Stress and More. Oxid Med Cell Longev. 2016;2016:2986796.
[23] Liu W, Zhou Y, Qin Y, et al. Quercetin Intervention Alleviates Offspring's Oxidative Stress, Inflammation, and Tight Junction Damage in the Colon Induced by Maternal Fine Particulate Matter (PM2.5) Exposure through the Reduction of Bacteroides. Nutrients. 2020;12(10):E3095.
[24] Sahoo PK, Pradhan LK, Aparna S, Agarwal K, Banerjee A, Das SK. Quercetin abrogates bisphenol A induced altered neurobehavioral response and oxidative stress in zebrafish by modulating brain antioxidant defence system. Environ Toxicol Pharmacol. 2020;80:103483.
[25] Wang J, Zhu H, Wang K, Yang Z, Liu Z. Protective effect of quercetin on rat testes against cadmium toxicity by alleviating oxidative stress and autophagy. Environ Sci Pollut Res Int. 2020;27(20):25278-86.
[26] Sandoval-Acuña C, Ferreira J, Speisky H. Polyphenols and mitochondria: an update on their increasingly emerging ROS-scavenging independent actions. Arch Biochem Biophys. 2014;559:75-90.
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