Life Extension Super K
vs
21st Century Vitamin C
Supplement Comparison

  • Vitamin C: 21st Century Vitamin C has 50× more
  • The image below shows:
    • Side-by-side charts with label nutrient amounts, per serving
    • Nutrient forms as listed on the label
    • 8 nutrients compared
Bar chart: per-serving label amounts and listed forms for Life Extension Super K vs 21st Century Vitamin C.

Try the VIOscan dashboard demo for free

Build comparison charts in seconds – no signup or card needed

This is a free preview of the $9.99/month premium dashboard

Use the interactive demo with multivitamins samples

Try Free Demo

Frequently asked questions

Which active ingredients does Life Extension Super K have?

  • Vitamin C appears as Ascorbyl Palmitate
  • Vitamin K appears as Vitamin K1 Phytonadione
  • Vitamin K appears as Vitamin K2 Menaquinone-4 (MK-4)
  • Vitamin K appears as Vitamin K2 trans MK-7 K2VITAL

Which active ingredients does 21st Century Vitamin C have?

  • Vitamin C appears as Ascorbic Acid
  • Calcium appears as Calcium Carbonate

Which categories do Life Extension Super K and 21st Century Vitamin C belong to?

  • Single Vitamin

What health concerns do Life Extension Super K and 21st Century Vitamin C address?

  • Heart & Cardiovascular Health
  • Joint & Bone Health
  • Antioxidant Support
  • Immune System Support

Which product has a higher amount of Vitamin C per serving?

  • 21st Century Vitamin C has the highest total amount of Vitamin C: 500 mg per serving

How do the serving sizes compare between the two supplements?

  • Serving size:
    • Life Extension Super K: 1 softgel
    • 21st Century Vitamin C: 1 tablet
  • Vitamin C
    • This supplement has 10 mg
    • Recommended Dietary Allowance in men: 90 mg
    • Recommended Dietary Allowance in women: 75 mg
    • Tolerable Upper Intake Level: 2000 mg
  • Vitamin K
    • This supplement has 2600 mcg
    • Adequate Intake in men: 120 mcg
    • Adequate Intake in women: 90 mcg
    • Tolerable Upper Intake Level: Not established
  • Vitamin C
    • This supplement has 500 mg
    • Recommended Dietary Allowance in men: 90 mg
    • Recommended Dietary Allowance in women: 75 mg
    • Tolerable Upper Intake Level: 2000 mg
  • Calcium
    • This supplement has 30 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg

Last updated: February 13, 2026

  • Sources & Methodology: Nutrient data and forms are taken directly from Supplement Facts labels. Reviewed and standardized by the VIOscan Research Team. Learn more on the Methodology page.
  • We show the Recommended Dietary Allowance (RDA) when available. If no RDA exists, we show the Adequate Intake (AI). Tolerable Upper Intake Levels (UL) are used for upper limits. Unless otherwise noted, RDAs shown correspond to healthy adults aged 19–50 years and are sex-specific. Separate values exist for 51–70 years and >70 years, and pregnancy and lactation are excluded. All values come from the Dietary Reference Intakes (DRIs) published by the National Academies of Sciences, Engineering, and Medicine (NASEM), Food and Nutrition Board (FNB).
  • Transparency: We’re funded by our users. We don’t have sponsors or affiliate links, and we don’t sell supplements.
  • Editorial standards: we provide independent, impartial and objective data analysis.
  • This analysis is for educational purposes only. It is not a substitute for medical advice.
  • Questions? Read our Frequently Asked Questions or contact us, we’re here to help.
  • See an error? Report it through our Contact page.
  • Author: VIOscan Research Team