Evidence Tiers — From DRI to RCTs to Influencers

Core topics

Lessons in this module

Learning objectives

By the end of this module you will be able to

Lesson summary ↓Graded claims ↓Self-check ↓Vignettes ↓Glossary ↓

L01
Define DRI/EAR/RDA/AI/UL and identify when each applies.
L02
Apply GRADE downgrading factors to a supplement RCT.
L03
Recall the indications and surprising negative results of ATBC, CARET, SELECT, and VITAL.
L04
Distinguish surrogate outcomes (LDL, hsCRP, HRV) from hard outcomes (MACE, mortality).
L05
Assign a defensible evidence tier to a novel claim within 60 seconds.

Expected takeaways

What you should walk away believing

→RDA is set at the EAR + 2 SD — not an optimum, not a ceiling.
→UL is the safe daily intake — exceeding it requires explicit justification.
→Many surrogate-positive supplements failed at hard-outcome endpoints.
→Conflict of interest disclosure is mandatory but variably reported in supplement journals.

Lesson · Core emphasis

What this means for you

Patient summary

There's a hierarchy of evidence, from 'one person on YouTube' to 'large randomized trial.' Population-level vitamin studies have surprised us — many things that looked good in lab work didn't help, or even hurt, when tested properly.

Clinician summary

Use GRADE as your default appraisal framework. Anchor counseling to: (1) deficiency state with biomarker, (2) RCT in matched population with hard outcome, (3) absence of either. Flag conflict of interest when industry-sponsored.

Advanced note

Read Pocock's 'Surrogate Endpoints' (NEJM 1998) and Ioannidis 'Why Most Published Research Findings Are False' (PLoS Med 2005) for the meta-level framework.

Evidence framework

Where this module sits on the device evidence map

Tier framework — applies to every subsequent module.

Tier map →Tier 1 →Tier 2 →Tier 3 →

Myth-buster

If a vitamin lowers a biomarker, it must improve outcomes.

Reality

Niacin (HPS2-THRIVE, AIM-HIGH) lowered LDL/raised HDL but failed mortality endpoints and increased harm.

Evidence-graded claims

What the data says

A

GRADE is the dominant guideline-methodology framework

Used by WHO, NICE, USPSTF, ACP.

F

Surrogate outcomes reliably predict hard outcomes for supplements

Repeatedly refuted.

B

Industry funding biases supplement-trial conclusions

Documented in multiple bibliometric reviews.

Objective self-check

Test the learning objectives

Score0 / 1(0 answered)

Q1L01 — UL is:

Case vignettes

Apply it: real-world counseling scenarios

Short patient encounters that test your judgment, not your recall. Pick the most defensible response, then reveal the rationale and a sample coaching script you could actually say at the bedside.

Vignette proficiency

In progress · 0/1 submitted

Correct0/1 (0%)Pitfalls avoided0/0 (0%)Composite0

Composite weighting

Accuracy 60%Pitfalls 40%

← all pitfallsbalancedall accuracy →

Composite = 60% answer accuracy + 40% pitfalls avoided. Your weighting is saved for this module.

Order · randomized[1]

Vignette 1 of 1· source #1

Niacin pitch

Objective · Surrogate vs hard outcomes.

A 60-year-old asks if high-dose niacin will prevent his next heart attack.

Best response?

Quick check

Test yourself

Q1UL is:

Q2Which trial showed harm from beta-carotene in smokers?

Q3GRADE downgrades evidence for:

Flashcards · Spaced repetition

Lock it in — review what's due

Due3Total3

FrontNew

3 in queue

EAR vs RDA?

Click to reveal answer

Glossary

Key terms & abbreviations

DRI: Dietary Reference Intakes — umbrella term covering EAR, RDA, AI, UL.
RDA: Recommended Daily Allowance — meets ~97.5% of population's needs.
UL: Tolerable Upper Intake Level — daily intake unlikely to cause adverse effects.
GRADE: Grading of Recommendations Assessment, Development and Evaluation — dominant evidence-quality framework.

Optional deeper dive

GRADE handbook — gradepro.org↗
VITAL trial — Manson et al. — NEJM 2019↗