21st Century Sentry Adults
vs
Douglas Laboratories Hair, Skin and Nails Plus
Supplement Comparison

  • Magnesium: Douglas Laboratories Hair, Skin and Nails Plus has 10% more
  • Vitamin C: Douglas Laboratories Hair, Skin and Nails Plus has 4.2% more
  • Zinc: 21st Century Sentry Adults has 47% more
  • The image below shows:
    • Side-by-side charts with label nutrient amounts, per serving
    • Nutrient forms as listed on the label
    • 57 nutrients compared
Bar chart: per-serving label amounts and listed forms for 21st Century Sentry Adults vs Douglas Laboratories Hair, Skin and Nails Plus.

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Frequently asked questions

Which active ingredients does 21st Century Sentry Adults have?

  • Vitamin A appears as Retinyl Acetate and Beta-Carotene
  • Vitamin C appears as Ascorbic Acid
  • Vitamin D appears as Cholecalciferol (D3)
  • Vitamin E appears as dl-Alpha Tocopheryl Acetate
  • Vitamin K appears as Vitamin K1 Phytonadione
  • Vitamin B1 (Thiamin) appears as Thiamin Mononitrate
  • Vitamin B2 (Riboflavin) appears as Riboflavin
  • Vitamin B3 (Niacin) appears as Niacinamide
  • Vitamin B6 (Pyridoxine) appears as Pyridoxine HCl
  • Vitamin B9 (Folate) appears as Folic Acid
  • Vitamin B12 (Cobalamin) appears as Cyanocobalamin
  • Vitamin B7 (Biotin)
  • Vitamin B5 (Pantothenic Acid) appears as D-Calcium Pantothenate
  • Calcium appears as Calcium Carbonate and Dicalcium Phosphate
  • Iron appears as Ferrous Fumarate
  • Phosphorus appears as DiCalcium Phosphate
  • Iodine appears as Potassium Iodide
  • Magnesium appears as Magnesium Oxide
  • Zinc appears as Zinc Oxide
  • Selenium appears as Sodium Selenate
  • Copper appears as Copper Sulfate
  • Manganese appears as Manganese Sulfate
  • Chromium appears as Chromium Picolinate
  • Molybdenum appears as Sodium Molybdate
  • Chloride appears as Potassium Chloride
  • Potassium appears as Potassium Chloride

Which active ingredients does Douglas Laboratories Hair, Skin and Nails Plus have?

  • Vitamin A appears as Retinyl Palmitate
  • Vitamin C appears as Vitamin C Complex (calcium ascorbate, magnesium ascorbate, manganese ascorbate, ascorbic acid)
  • PABA
  • Calcium appears as Calcium Complex (calcium malate, citrate, ascorbate)
  • Iron appears as Ferronyl Iron
  • Magnesium appears as Magnesium Malate
  • Zinc appears as Zinc Krebs Complex (citrate, fumarate, malate, glutarate, succinate, ascorbate)
  • Manganese appears as Manganese Citrate and Ascorbate
  • Citrus Bioflavonoid Complex
  • Horsetail (Equisetum arvense) Extract
  • Sunflower Lecithin appears as Lecithin (from soy, high in phosphatidylcholine)
  • Gelatin

Which categories do 21st Century Sentry Adults and Douglas Laboratories Hair, Skin and Nails Plus belong to?

  • Multivitamin

What health concerns do 21st Century Sentry Adults and Douglas Laboratories Hair, Skin and Nails Plus address?

  • General Health
  • Skin, Hair & Nail Health

Which product has a higher amount of Magnesium per serving?

  • Douglas Laboratories Hair, Skin and Nails Plus has the highest total amount of Magnesium: 55 mg per serving

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

  • Douglas Laboratories Hair, Skin and Nails Plus has the highest total amount of Vitamin C: 62.5 mg per serving

Which product has a higher amount of Zinc per serving?

  • 21st Century Sentry Adults has the highest total amount of Zinc: 11 mg per serving

How do the serving sizes compare between the two supplements?

  • Serving size:
    • 21st Century Sentry Adults: 1 tablet
    • Douglas Laboratories Hair, Skin and Nails Plus: 2 capsules
  • Vitamin A
    • This supplement has 1050 mcg RAE
    • Recommended Dietary Allowance in men: 900 mcg RAE
    • Recommended Dietary Allowance in women: 700 mcg RAE
    • Tolerable Upper Intake Level: 3000 mcg RAE
  • Vitamin C
    • This supplement has 60 mg
    • Recommended Dietary Allowance in men: 90 mg
    • Recommended Dietary Allowance in women: 75 mg
    • Tolerable Upper Intake Level: 2000 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
  • Vitamin E
    • This supplement has 13.5 mg
    • Recommended Dietary Allowance in men: 15 mg
    • Recommended Dietary Allowance in women: 15 mg
    • Tolerable Upper Intake Level: 1000 mg
  • Vitamin K
    • This supplement has 25 mcg
    • Adequate Intake in men: 120 mcg
    • Adequate Intake in women: 90 mcg
    • Tolerable Upper Intake Level: Not established
  • Vitamin B1 (Thiamin)
    • This supplement has 1.5 mg
    • Recommended Dietary Allowance in men: 1.2 mg
    • Recommended Dietary Allowance in women: 1.1 mg
    • Tolerable Upper Intake Level: Not established
  • Vitamin A
    • This supplement has 2250 mcg RAE
    • Recommended Dietary Allowance in men: 900 mcg RAE
    • Recommended Dietary Allowance in women: 700 mcg RAE
    • Tolerable Upper Intake Level: 3000 mcg RAE
  • Vitamin C
    • This supplement has 62.5 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 80 mg
    • Recommended Dietary Allowance in men: 1000 mg
    • Recommended Dietary Allowance in women: 1000 mg
    • Tolerable Upper Intake Level: 2500 mg
  • Iron
    • This supplement has 7.5 mg
    • Recommended Dietary Allowance in men: 8 mg
    • Recommended Dietary Allowance in women: 18 mg
    • Tolerable Upper Intake Level: 45 mg
  • Zinc
    • This supplement has 7.5 mg
    • Recommended Dietary Allowance in men: 11 mg
    • Recommended Dietary Allowance in women: 8 mg
    • Tolerable Upper Intake Level: 40 mg
  • Manganese
    • This supplement has 5 mg
    • Adequate Intake in men: 2.3 mg
    • Adequate Intake in women: 1.8 mg
    • Tolerable Upper Intake Level: 11 mg

Last updated: February 20, 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