Tools · Supplement Guide

The Supplement Guide,
Graded by Evidence.

A searchable reference to the 50 most commonly used supplements — what the research actually shows, the dose studies used, the realistic size of the effect, and the safety notes worth knowing before recommending anything to a client.

50
Supplements covered
4
Evidence grades (A–D)
11
Categories

What This Guide Is — and Isn't — For

Supplementation is one of the most-asked-about topics in coaching, and one of the easiest to overstep scope on. This guide is built to support education, not prescription.

Use This Guide To

  • Explain what a supplement does and how strong the evidence actually is
  • Share the dosing ranges used in the research, as general education
  • Set realistic expectations about the size of an effect — most are small
  • Flag safety considerations and drug interactions worth a physician conversation
  • Help a client understand why a popular supplement may not be worth their money
  • Point clients toward a physician or pharmacist for personalized dosing

Don't Use This Guide To

  • Diagnose a deficiency or medical condition
  • Prescribe an individualized dose for treating a condition
  • Tell a client to stop or start a medication
  • Override a physician's or pharmacist's guidance on interactions
  • Recommend a supplement as a substitute for medical care

How to Read the Evidence Grade

Every entry is graded against its single best-supported, most commonly claimed use — not a vague overall impression. A supplement can have real value for one purpose and none for another; where that's the case, the effect-size text spells out the difference.

A
Strong evidence
Consistent, well-replicated RCT or meta-analysis evidence for a specific, meaningful outcome.
B
Moderate evidence
Real, generally positive evidence, but mixed trial quality, a narrower population, or a smaller effect.
C
Limited / preliminary
Early, small, or inconsistent trials. Plausible, but not yet established — evidence could shift either way.
D
No evidence / debunked
Well-studied and shown not to work for its marketed claim, or no credible evidence exists at all.
No supplements match those filters. Try clearing one or more filters above.

Where This Comes From

This guide is for coach and client education only — it is not medical advice and does not replace a conversation with a physician or pharmacist, especially for anyone on medication, pregnant or breastfeeding, or managing a health condition. Dosing shown reflects what was used in research, not an individualized recommendation.

Evidence grades, dosing ranges, and effect sizes were compiled from the Science of Nutrition Coaching textbook (Ch. 11: Supplements), NIH Office of Dietary Supplements fact sheets, Cochrane Database systematic reviews, and peer-reviewed meta-analyses / RCTs — a specific citation is listed on every entry's "Key research" line below its detail panel.

References (88)
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Built for FITTR coaches and clients · Evidence grades reflect the research available as of 2026 and may be revised as new studies are published.