B12 Deficiency Prevalence Among Vegetarians

Pawlak R et al. • Nutr Rev

Key Finding

25-86% of vegetarians are B12 deficient

Original title: “How prevalent is vitamin B12 deficiency among vegetarians?”

Plain English Summary

Systematic review finding high prevalence of B12 deficiency among vegetarians and vegans, ranging from 25% to 86% depending on study population.

In-Depth Analysis

Background

Dr. Roman Pawlak and colleagues published this systematic review in Nutrition Reviews (PMID: 23356638), examining the prevalence of B12 deficiency among vegetarians and vegans.

Study Design

Design: Systematic review Search: PubMed, CINAHL through 2012 Included: Studies measuring B12 status in vegetarian/vegan populations Analysis: Prevalence rates by dietary pattern and duration

Key Findings

B12 deficiency prevalence by diet type:

Dietary Pattern	Deficiency Rate
Vegans	52-86%
Lacto-ovo vegetarians	25-50%
Long-term vegetarians (>5 years)	Higher rates
Vegetarian children	25-86%

Definition used: Serum B12 <200 pg/mL or elevated MMA

Risk factors for higher deficiency:

•Longer duration of vegetarian diet
•Vegan vs. lacto-ovo vegetarian
•No supplementation
•Pregnancy/lactation

Mechanistic Insights

B12 is found almost exclusively in animal foods:

•Meat, fish, eggs, dairy contain reliable amounts
•Plant foods contain no active B12 (some analogs may interfere)
•Body stores last 2-5 years after stopping intake
•Deficiency develops insidiously

Clinical Implications

All vegans and most vegetarians should supplement B12. Testing recommended regularly (every 1-2 years). MMA testing identifies early tissue deficiency before serum B12 falls.

Metabolic Health Perspective

Plant-based diets can support metabolic health but require B12 attention. Functional deficiency (elevated MMA, normal B12) can cause symptoms. Target: serum B12 >500 pg/mL with supplementation.