How Malnutrition Causes Anemia
Malnutrition causes anemia through multiple mechanisms, primarily through deficiencies of iron, vitamin B12, and folate, which are essential for normal erythropoiesis and hemoglobin synthesis. 1
Key Nutritional Deficiencies Leading to Anemia
Iron Deficiency
- Primary mechanism: Insufficient dietary iron intake leads to inadequate hemoglobin synthesis
- Iron is essential for hemoglobin production, which carries oxygen in red blood cells
- Presents as microcytic, hypochromic anemia (low MCV)
- Diagnosed by:
- Serum ferritin <30 μg/L (without inflammation)
- Serum ferritin <100 μg/L (with inflammation) 1
- Low transferrin saturation
Vitamin B12 Deficiency
- Causes megaloblastic, macrocytic anemia (high MCV)
- Essential for DNA synthesis and normal erythrocyte maturation
- Leads to impaired cell division and abnormal red blood cell development
- May cause neurological symptoms if severe
- Common in strict vegetarians or those with malabsorption 1
Folate Deficiency
- Also causes megaloblastic, macrocytic anemia
- Critical for DNA synthesis and cell division
- May indicate poor dietary intake or malabsorption
- Can be affected by medications like anticonvulsants, sulfasalazine, and methotrexate 1
- Important: Folate supplementation may mask severe vitamin B12 deficiency, potentially leading to neurological damage 1
Additional Mechanisms
Protein-Energy Malnutrition
- Causes inadequate substrate for protein synthesis in hematopoietic cells 1
- Protein malnutrition can present several years after bariatric surgery 1
- Associated with chronic inflammation and intestinal barrier dysfunction 1
Micronutrient Interactions
- Copper and zinc deficiencies can affect iron absorption and utilization 2
- Vitamin D deficiency often coexists with anemia in malnourished patients 3
- Chronic inflammation from malnutrition alters iron metabolism (increases ferritin despite iron deficiency) 1
Clinical Presentations
Types of Anemia in Malnutrition
- Microcytic anemia (38.6%): Most common in severe acute malnutrition 4
- Megaloblastic anemia (30.5%): Second most common 4
- Mixed deficiency patterns are common in malnourished patients 3
High-Risk Populations
- Children with severe acute malnutrition (67.3% have severe anemia) 4
- Elderly receiving home care (37.9% have anemia) 3
- Patients after bariatric surgery 1
- HIV-infected individuals (with altered ferritin levels due to inflammation) 1
Diagnostic Considerations
- Complete blood count with MCV is essential for classification
- Reticulocyte count helps determine if bone marrow is responding appropriately
- Serum ferritin interpretation must consider inflammation status:
- <15 μg/L confirms iron deficiency anemia
- Up to 100 μg/L may still indicate iron deficiency with inflammation 1
- Check vitamin B12 and folate levels in all cases of macrocytic anemia
- Consider C-reactive protein to assess inflammation when interpreting iron studies 1
Treatment Approach
- Always check vitamin B12 status before giving folate to avoid precipitating subacute combined degeneration of the spinal cord 1
- For iron deficiency: 60-120 mg elemental iron daily 5
- For vitamin B12 deficiency with neurological involvement: hydroxocobalamin 1 mg IM on alternate days until improvement 1
- For vitamin B12 deficiency without neurological involvement: hydroxocobalamin 1 mg IM three times weekly for 2 weeks 1
- For folate deficiency: oral folic acid 5 mg daily for minimum 4 months 1, 6
- Address underlying malnutrition with appropriate dietary intervention
Prevention Strategies
- Comprehensive nutritional assessment at each clinical encounter 1
- Screening for recent weight loss and malnutrition risk
- Adequate dietary protein (1.2-1.5 g/kg body weight) 5
- Iron-rich foods paired with vitamin C sources to enhance absorption 5
- Consider prophylactic supplementation in high-risk groups
Remember that anemia in malnourished patients is often multifactorial, and addressing the underlying nutritional deficiencies is essential for effective treatment and prevention of recurrence.