NOW C-500 Ascorbate: Stomach-Friendly Buffered Vitamin C with Bioflavonoids
NOW C-500 Ascorbate delivers 500 mg of non-acidic vitamin C per capsule in the form of calcium ascorbate, buffered specifically to neutralize acidity and eliminate the gastric burn, acid reflux, and digestive upset common with standard ascorbic acid. Reinforced with 55 mg of bioavailable calcium and 10 mg of synergistic citrus bioflavonoids, this formula provides sustained antioxidant protection and collagen support while remaining gentle on sensitive digestive tracts.
At-a-Glance Highlights
Buffered & Non-Acidic: Calcium-bound ascorbate maintains a near-neutral pH to protect sensitive stomach linings.
Synergistic Absorption: Fortified with citrus bioflavonoids to support cellular retention and vascular strength.
Rigorous Purity: Screened down to parts-per-billion in ISO/IEC 17025 accredited analytical laboratories for heavy metals and contaminants.
Clean Formulation: Non-GMO, vegan/vegetarian capsules, free of gluten, dairy, soy, and synthetic binders.
The Science of Buffered Vitamin C: Calcium Ascorbate vs. Ascorbic Acid
Most off-the-shelf vitamin C supplements use unbuffered ascorbic acid. In pure form, ascorbic acid has an acidic pH between 2.5 and 3.0—comparable to the acidity of lemon juice or vinegar. While normal stomach acid can process this compound, taking 500 mg to 1,000 mg of raw ascorbic acid frequently causes gastric irritation, nausea, cramping, and acid reflux in sensitive individuals.
Calcium ascorbate solves this challenge through a simple biochemical reaction: ascorbic acid is bound to calcium carbonate, neutralizing its acidic nature into a buffered mineral salt with a gentle pH between 6.8 and 7.4. When dissolved in your digestive tract, it delivers active L-ascorbate without altering gastric equilibrium.
Key Parameter
Standard Ascorbic Acid
NOW C-500 Ascorbate (Calcium Ascorbate)
Acidity Level (pH)
Highly acidic (~2.5 to 3.0)
Neutral / Buffered (~6.8 to 7.4)
Stomach Tolerance
High incidence of heartburn and epigastric discomfort
Gentle on gastric mucosa; well-tolerated on empty stomachs
Supplemental Mineral
None (0 mg calcium)
Yields 55 mg elemental calcium per capsule
Bioflavonoid Synergists
Rarely included in basic formulas
Includes 10 mg Citrus Bioflavonoid Complex
Peer-Reviewed Clinical Citations & Mechanisms
Gastric Tolerance: In a randomized, double-blind crossover trial, researchers observed that buffered calcium ascorbate produced significantly fewer epigastric adverse effects and was better tolerated by subjects prone to gastric irritation compared to plain ascorbic acid (Gruenwald et al., Advances in Therapy, 2006; 23(1):171-178).
Bioflavonoid Bioavailability: Clinical pharmacokinetic evaluations show that citrus bioflavonoids work synergistically with ascorbic acid, retarding its oxidation in the gut and slowing urinary elimination for improved tissue bioavailability (Vinson & Bose, American Journal of Clinical Nutrition, 1988; 48(3):601-604).
Enzymatic Collagen Cross-Linking: Vitamin C operates as an obligatory cofactor for prolyl and lysyl hydroxylase enzymes, ensuring structural stabilization of the triple-helix collagen matrix in skin, tendons, and cartilage (Pullar et al., Nutrients, 2017; 9(8):866).
Every ingredient in NOW C-500 Ascorbate (Product SKU: N0677) is fully disclosed without proprietary chemical hiding. The supplement facts have been cross-checked directly with manufacturer product records:
Supplement Facts
Serving Size: 1 Veg Capsule
Servings Per Container: 100 or 250
Amount Per Serving
% Daily Value
Vitamin C (from Calcium Ascorbate) 500 mg
556%
Calcium (from Calcium Ascorbate) 55 mg
4%
Citrus Bioflavonoid Complex 10 mg
†
† Daily Value not established.
Excipients, Allergens, & Dietary Specifications
Other Ingredients: Hypromellose (plant-derived cellulose capsule), Microcrystalline Cellulose, and Stearic Acid (vegetable source).
Allergen Declaration: Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish, or tree nut ingredients. Produced in an audited GMP facility that processes other ingredients containing these allergens.
NOW Foods Quality Control: ISO 17025 Labs & Strict Contaminant Constraints
Vitamin C is one of the most widely counterfeited and adulterated raw materials in the global supplement supply chain. To verify absolute potency and biological safety, NOW Foods subjects every batch of raw materials and finished capsules to rigorous multi-tier analytical screening in its dedicated, world-class testing facilities.
✓ ISO/IEC 17025:2017 Accredited Laboratories
NOW operates advanced in-house analytical testing laboratories accredited by the American Association for Laboratory Accreditation (A2LA). Employing more than 160 chemists, microbiologists, and toxicologists, the testing campus performs over 19,000 to 37,000 individual assays per month.
✓ Parts-Per-Billion Heavy Metal Screening (ICP-MS)
Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), NOW tests for toxic heavy metals down to parts-per-billion (ppb) detection limits. Every production run is audited for lead, arsenic, cadmium, and mercury to ensure strict compliance with USP monographs and California Proposition 65 limits.
✓ HPLC Potency & Identity Fingerprinting
High-Performance Liquid Chromatography (HPLC) and Fourier-Transform Infrared Spectroscopy (FTIR) verify that each capsule contains the exact 500 mg label claim of bioactive L-ascorbate without synthetic adulterants, degradation byproducts, or incorrect salt ratios.
✓ Comprehensive Microbiological & Residue Defense
Raw ingredients are quarantined and screened for microbial pathogens (including Salmonella, E. coli, and Staphylococcus aureus), total yeasts and molds, residual solvents, and broad-spectrum agricultural pesticides before release into manufacturing.
Health Benefits, Safe Dosing & Critical Medical Contraindications
Vitamin C is an essential water-soluble nutrient that your body cannot synthesize internally. Daily intake directly fuels multiple critical biological processes:
White Blood Cell Activation: Ascorbate accumulates in neutrophils and lymphocytes at concentrations up to 80-fold higher than in blood plasma, stimulating white blood cell motility and phagocytosis during immune challenges (Carr & Maggini, Nutrients, 2017; 9(11):1211).
Collagen & Tissue Repair: Essential for maintaining structural collagen in joints, ligaments, capillary walls, gums, and dermal layers.
Potent Free Radical Scavenging: Neutralizes reactive oxygen species (ROS) generated by metabolic stress, UV exposure, and intense exercise, protecting DNA and lipid membranes from cellular oxidation.
Non-Heme Iron Absorption: Ascorbate converts dietary ferric iron ($Fe^{3+}$) to ferrous iron ($Fe^{2+}$) in the duodenum, substantially increasing mineral uptake from plant foods.
Clinical Precautions: Who Should NOT Take High-Dose Calcium Ascorbate?
While buffered vitamin C is exceptionally gentle on digestion, consumers must consider specific metabolic interactions:
History of Calcium-Oxalate Kidney Stones: Excess ascorbic acid can metabolize into urinary oxalate. Individuals with hyperoxaluria or recurrent kidney stones should consult a nephrologist before exceeding 500 mg daily (Ferraro et al., Am J Kidney Dis., 2016).
Hypercalcemia: Because each capsule provides 55 mg of elemental calcium, individuals with severe kidney dysfunction or hyperparathyroidism should account for this mineral contribution.
Hemochromatosis / Iron Overload: Due to vitamin C's ability to significantly enhance dietary iron absorption, individuals diagnosed with hemochromatosis should avoid high supplemental dosages.
Suggested Daily Intake: Take 1 capsule 1 to 3 times daily, preferably with meals, or as directed by your healthcare professional. Do not exceed the safe tolerable upper intake level (UL) of 2,000 mg/day unless under medical supervision.
Why Choose VitaNet® for Your NOW C-500 Ascorbate
Purchasing vitamins online should never feel like a gamble with unverified marketplace sellers, damaged inventory, or expired warehouse stock. Founded in 1995 as an independent, family-owned retailer based in Hartville, Ohio, VitaNet®, LLC brings over 30 years of hands-on nutritional retail experience directly to your doorstep[cite: 1].
The VitaNet Customer Guarantee
100% Unconditional Money-Back Guarantee: If NOW C-500 Ascorbate does not agree with your stomach or meet your expectations, VitaNet provides a complete refund and even pays the return shipping costs—even on opened bottles[cite: 1].
Direct Manufacturer Sourcing: All NOW inventory is delivered fresh directly from regulated production facilities into climate-controlled storage, guaranteeing potency until the printed expiration date.
BBB A+ Accredited Heritage: Shop with confidence supported by accessible telephone customer care from trained, independent nutritional retail specialists[cite: 1].
Frequently Asked Questions (FAQ)
What makes NOW C-500 Ascorbate different from standard ascorbic acid?
Standard ascorbic acid is highly acidic (pH 2.5-3.0), which can irritate stomach tissue and provoke acid reflux. NOW C-500 Ascorbate binds ascorbic acid with calcium to create calcium ascorbate—a non-acidic, pH-buffered form (pH 6.8-7.4) that provides full-strength vitamin C while remaining very gentle on digestion.
Will NOW C-500 Ascorbate trigger acid reflux or stomach irritation?
Because this supplement is buffered to a near-neutral pH, it does not create the harsh acid surge caused by unbuffered vitamin C tablets. Clinical trials confirm buffered calcium ascorbate results in significantly fewer upper digestive complaints in sensitive individuals.
Why does this formula include citrus bioflavonoids?
Citrus bioflavonoids are natural plant polyphenols that accompany vitamin C in whole fruits. They work synergistically to protect ascorbate molecules from rapid oxidation, enhance absorption, and strengthen capillary wall flexibility.
How does NOW Foods ensure the purity and safety of its vitamin C?
NOW Foods tests each production batch in ISO/IEC 17025 accredited analytical laboratories using ICP-MS to detect heavy metals (lead, cadmium, arsenic, mercury) down to parts-per-billion, while using HPLC testing to ensure strict 500 mg active potency without microbiological contamination.
How should I take NOW C-500 Ascorbate for optimal results?
The suggested use is 1 vegetarian capsule taken 1 to 3 times daily, preferably with meals. Splitting your intake across the day ensures consistent, saturated blood levels of vitamin C.
What if this supplement does not work for me?
VitaNet backs every purchase with a 100% money-back guarantee[cite: 1]. If you are not satisfied for any reason, VitaNet will refund your purchase and cover return shipping, even on opened bottles[cite: 1].
