Fat-Soluble Vitamins — A, D, E, K

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
Identify clinical scenarios where vitamin D supplementation is indicated (deficiency, osteoporosis, malabsorption) vs not (CV prevention in repleted adults).
L02
Counsel on vitamin A teratogenicity and the >10,000 IU/d threshold.
L03
Explain why SELECT vitamin E + selenium increased prostate cancer.
L04
Manage warfarin patients with respect to vitamin K1 dietary and supplement intake.

Expected takeaways

What you should walk away believing

→Vitamin D RCTs in non-deficient adults (VITAL) failed to reduce CV/cancer endpoints; deficiency repletion remains evidence-based.
→Routine high-dose vitamin E or A in well-nourished adults: no benefit, demonstrated harm.
→Vitamin K2 (MK-7) bone/CV claims are largely Tier 3 — promising preclinical, weak human RCT.
→Beware acute-on-chronic vitamin A toxicity — pseudotumor cerebri, hepatic injury.

Lesson · Core emphasis

What this means for you

Patient summary

Vitamin D matters when you're deficient — usually checked with a blood test. Vitamins A and E in large doses can be harmful, not helpful. If you take warfarin, talk to your doctor before changing how much vitamin K you eat or take.

Clinician summary

Vitamin D: check 25-OH-D in at-risk patients, repletion 1000–2000 IU/d (50,000 IU/wk for severe deficiency × 6–8 wk). Vitamin A: avoid >10,000 IU/d, contraindicated >3000 mcg RAE in pregnancy. Vitamin E: do not supplement above RDA without indication (e.g., NASH per AASLD). Vitamin K: maintain stable intake on warfarin.

Advanced note

VITAL substudies and D2d trial reframe vitamin D as a deficiency-repletion question, not a universal preventive. Mendelian randomization studies generally null for CV/cancer endpoints.

Evidence framework

Where this module sits on the device evidence map

Fat-soluble vitamins: strongest deficiency-rescue data; population-prevention claims have repeatedly failed.

Tier map →Tier 1 →Tier 2 →Tier 3 →

Myth-buster

Higher vitamin D blood levels are always better.

Reality

Hypercalcemia, hypercalciuria, nephrolithiasis above ~150 ng/mL; intervention trials show no incremental benefit above ~30 ng/mL.

Evidence-graded claims

What the data says

B

Vitamin D supplementation reduces fractures in deficient older adults with calcium

Modest benefit when combined with Ca²⁺ and baseline deficiency.

F

Vitamin E supplementation reduces cardiovascular events

HOPE, GISSI-Prevenzione, HPS negative.

A

Vitamin A supplementation reduces childhood mortality in deficient populations

Established in WHO-endorsed programs.

D

Vitamin K2 (MK-7) reverses arterial calcification

Preclinical and small trials; insufficient.

Objective self-check

Test the learning objectives

Score0 / 1(0 answered)

Q1L01 — Vit E supplementation in well-nourished adults:

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

Megadose vitamin D

Objective · Recognize hypervitaminosis D.

A 65-year-old self-treats with 50,000 IU vit D daily for 6 months. Now confused, polyuric.

Most likely lab abnormality?

Quick check

Test yourself

Q1Pregnancy teratogenic threshold for vitamin A?

Q2VITAL trial result?

Flashcards · Spaced repetition

Lock it in — review what's due

Due2Total2

FrontNew

2 in queue

Deficiency 25-OH-D cutoff?

Click to reveal answer

Glossary

Key terms & abbreviations

RAE: Retinol Activity Equivalent — standardizes vitamin A across forms.
25-OH-D: Calcidiol — main circulating vitamin D form; clinical marker of status.

Optional deeper dive

VITAL — Manson et al. — NEJM 2019↗
SELECT — Klein et al. — JAMA 2011↗