21st Century Calcium Citrate +D3 Maximum
vs
Douglas Laboratories Methylated Resveratrol Plus
Supplement Comparison

  • Vitamin D: Douglas Laboratories Methylated Resveratrol Plus has 2.0× more
  • The image below shows:
    • Side-by-side charts with label nutrient amounts, per serving
    • Nutrient forms as listed on the label
    • 11 nutrients compared
Bar chart: per-serving label amounts and listed forms for 21st Century Calcium Citrate +D3 Maximum vs Douglas Laboratories Methylated Resveratrol Plus.

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Frequently asked questions

Which active ingredients does 21st Century Calcium Citrate +D3 Maximum have?

  • Vitamin D appears as Cholecalciferol (D3)
  • Calcium appears as Calcium Citrate

Which active ingredients does Douglas Laboratories Methylated Resveratrol Plus have?

  • Vitamin D appears as Cholecalciferol (D3)
  • Resveratrol appears as resVida Resveratrol (trans-resveratrol)
  • Turmeric appears as Meriva Curcumin Phytosome
  • Pterostilbene appears as pTeroPure Pterostilbene (methylated resveratrol)
  • Blend appears as Cruciferous Vegetable and Fruit Blend (Wasabia japonica, Broccoli Sprout Powder, Pomegranate Powder)

Which categories do 21st Century Calcium Citrate +D3 Maximum and Douglas Laboratories Methylated Resveratrol Plus belong to?

  • Single Mineral
  • Antioxidant Complex

What health concerns do 21st Century Calcium Citrate +D3 Maximum and Douglas Laboratories Methylated Resveratrol Plus address?

  • Joint & Bone Health
  • Antioxidant Support
  • Metabolic Support
  • Healthy Aging & Longevity

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

  • Douglas Laboratories Methylated Resveratrol Plus has the highest total amount of Vitamin D: 1000 IU per serving

How do the serving sizes compare between the two supplements?

  • Serving size:
    • 21st Century Calcium Citrate +D3 Maximum: 2 tablets
    • Douglas Laboratories Methylated Resveratrol Plus: 1 capsule
  • Vitamin D
    • This supplement has 500 IU
    • Recommended Dietary Allowance in men: 600 IU
    • Recommended Dietary Allowance in women: 600 IU
    • Tolerable Upper Intake Level: 4000 IU
  • Calcium
    • This supplement has 630 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg
  • Vitamin D
    • This supplement has 1000 IU
    • Recommended Dietary Allowance in men: 600 IU
    • Recommended Dietary Allowance in women: 600 IU
    • Tolerable Upper Intake Level: 4000 IU

Last updated: February 19, 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.
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  • Author: VIOscan Research Team