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C Extra + Quercetin

product on market Capsule Natural Factors Safety: 100/100
100/100

This product looks safe

  • No ingredients exceed tolerable upper intake levels
  • 50% of ingredients have research evidence
A Label Compliance Grade

What the Evidence Says

AI-generated · Qwen 3.6 · methodology

Vitamin C and quercetin are researched for their roles in supporting immune function and antioxidant activity. While vitamin C has strong evidence for health maintenance, the evidence for quercetin's specific efficacy in humans is more limited. These ingredients are generally well-tolerated when taken as directed.

AI-generated summary based on research evidence. Not medical advice.

Label

Product Label

Label for C Extra + Quercetin
Open Full PDF View on NIH DSLD →
Details

Label Data

1 Capsule(s)
Serving Size
Other Combinations
Product Type
50%
Evidence Coverage
Ingredients

Supplement Facts — Evidence Check

Vitamin C
500 mg (556% DV)
250 mg
Market median: 500.0mg (283 products) 174 studies (A:0, B:62)

Other Ingredients

Vegetarian Capsule Magnesium Stearate Stearic Acid Microcrystalline Cellulose Silicon Dioxide
Claims

Label Claims — Verification

Unverified Nutrient
Unverified All Other
Unverified Structure/Function
Info

Product Information

Directions for Use

Suggested Usage: 1 capsule per day or as directed by a health professional.

Warnings & Precautions

Cautions: As with any supplement, consult your health professional before use if you are pregnant, breastfeeding, or trying to conceive, or if you are taking medication, have a medical condition, or anticipate a surgery.

Keep out of reach of children.

Sealed for your protection. Do not use if seal is broken.

Formulation Notes

Our C Extra + Quercetin contains 500 mg of vitamin C and 250 mg of Quercetin. Vitamin C is a powerful antioxidant which supports healthy bones, cartilage, teeth and gums. It helps protect cells against free radical damage and vitamin C deficiencies in the daily diet, and supports healthy cell growth. Quercetin is one of the most well-known antioxidant bioflavonoids. A free radical scavenger, quercetin helps support healthy sinus, respiratory and immune system function.

Easy-to-swallow capsules as compared to similar size tablets.

Manufactured by Natural Factors to ensure safety and potency in accordance with Good Manufacturing Practices (GMP) of the FDA and Health Canada.

Contains no artificial colors, preservatives, or sweeteners; no dairy, starch, sugar, wheat, gluten, yeast, soy, corn, egg, fish, shellfish, animal products, salt, tree nuts, or GMOs.

Suitable for vegetarians/vegans

Immune Support

C Extra + Quercetin Bioflavanoids 500 mg / 250 mg

Additional Information

Isura Non-GMO - Mass Spec Documentation - Lab Tested

For freshness, store in a cool, dry place.

Product of Canada Recyclable container and label.

Item # Q057462

Metadata

Product Details

UPC / SKU0 68958 01398 5
DSLD Entry Date2021-04-22
Product TypeOther Combinations
FormCapsule
DSLD ID247524
Data Updated2026-04-11
Research

Research Evidence

184
Research Sources
55
Avg Quality
91
Systematic Review
75
Meta Analysis
7
Rct
7
Clinical Trial
2
Cochrane Review
1
Openfda Safety
B Treatment of gouty arthritis with traditional Chinese medicine decoction: Meta-analysis, network pharmacology analysis, and molecular docking
Meta Analysis Medicine 2024 PubMed DOI
B Effects of quercetin supplementation on lipid profile: A systematic review and meta-analysis of randomized controlled trials
Meta Analysis Critical reviews in food science and nutrition 2017 PubMed
B Dietary polyphenols and the risk of metabolic syndrome: a systematic review and meta-analysis
Meta Analysis BMC endocrine disorders 2024 PubMed DOI
B Quercetin and endurance exercise capacity: a systematic review and meta-analysis
Meta Analysis Medicine and science in sports and exercise 2011 PubMed DOI
B Dietary flavonoid intake and smoking-related cancer risk: a meta-analysis
Meta Analysis PloS one 2013 PubMed DOI
B Clinical efficacy evaluation and potential mechanism prediction on Guizhi-Shaoyao-Zhimu decoction in the treatment of gouty arthritis based on meta-analysis, network pharmacology analysis, and molecular docking
Meta Analysis Medicine 2023 PubMed DOI
B A Systematic Review: Quercetin-Secondary Metabolite of the Flavonol Class, with Multiple Health Benefits and Low Bioavailability
Systematic Review International journal of molecular sciences 2024 PubMed DOI
B Dietary flavonoid for preventing colorectal neoplasms.
Cochrane Review The Cochrane database of systematic reviews PubMed DOI
B Flavonoids for treating venous leg ulcers.
Cochrane Review The Cochrane database of systematic reviews PubMed DOI
B The effects of quercetin supplementation on lipid profiles and inflammatory markers among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trials
Meta Analysis Critical reviews in food science and nutrition 2020 PubMed DOI
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This product page is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before taking any supplement.