Learning Objective :

Identify dietary patterns associated with specific vitamin deficiencies and understand the underlying mechanisms and clinical relevance.

Dietary Supplementation and Associated Vitamin Deficiencies

Vegetarian/Vegan diets

• Vitamin B12 (Cobalamin): Found primarily in animal products; deficiency → megaloblastic anemia, neuropathy
• Iron: Reduced intake and lower bioavailability of non-heme iron
• Vitamin B2 (Riboflavin): Limited dairy intake may contribute
• Vitamin D: Frequently deficient (common across many diets, not exclusive to vegetarianism)

High intake of raw egg whites

• Vitamin B7 (Biotin): Avidin in raw egg whites binds biotin and prevents its absorption → dermatitis, alopecia, enteritis

Untreated corn–based diets

• Vitamin B3 (Niacin): Corn lacks bioavailable niacin unless treated (e.g., nixtamalization); deficiency leads to pellagra (dermatitis, diarrhea, dementia), especially in resource-limited settings

Key USMLE Pearl:

Diet-related vitamin deficiencies are best remembered by linking the dietary restriction or food component to the mechanism of impaired absorption or availability.

Activity