Common Nutritional Deficiencies

Why This Matters

As a nutrition nurse, you're often the first line of defense in identifying nutritional deficiencies before they escalate into serious complications. These deficiencies don't exist in isolation—they're interconnected through shared absorption pathways, overlapping symptoms, and common risk factors like malabsorption syndromes, dietary restrictions, life stage demands, and chronic disease states. Understanding the underlying mechanisms helps you move from reactive symptom management to proactive nutritional assessment.

You're being tested on more than just matching a deficiency to its symptoms. Certification exams and clinical practice require you to recognize at-risk populations, understand why certain deficiencies cluster together, and prioritize interventions based on severity and patient context. Don't just memorize lab values—know what physiological process each nutrient supports and how deficiencies manifest differently across patient populations.

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Blood Cell Production & Oxygen Transport

These deficiencies directly impair the body's ability to produce healthy red blood cells or carry oxygen effectively. The underlying mechanism involves disrupted hemoglobin synthesis or abnormal cell division in the bone marrow.

Iron Deficiency Anemia

• Most common nutritional deficiency worldwide—affects hemoglobin production, reducing oxygen-carrying capacity of red blood cells
• Key labs: low ferritin and hemoglobin—ferritin drops first, making it your earliest indicator before anemia develops
• High-risk populations include menstruating women, pregnant patients, and those with chronic GI bleeding—always assess for underlying blood loss, not just dietary intake

Vitamin B12 Deficiency

• Causes megaloblastic anemia AND neurological damage—the neuro symptoms (numbness, memory issues) can become permanent if untreated
• Absorption requires intrinsic factor from parietal cells—patients with gastric surgery, pernicious anemia, or long-term PPI use are at high risk
• Diagnosis includes serum B12 and methylmalonic acid (MMA)—elevated MMA confirms functional deficiency even when B12 levels appear borderline

Folate (Vitamin B9) Deficiency

• Critical for DNA synthesis and neural tube development—deficiency in early pregnancy causes spina bifida and anencephaly
• Also causes megaloblastic anemia identical to B12 deficiency on CBC—but folate deficiency lacks the neurological symptoms
• High-risk groups: pregnant women, alcohol use disorder, methotrexate patients—certain medications act as folate antagonists

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Bone Health & Calcium Regulation

These nutrients work synergistically to maintain skeletal integrity. Vitamin D enables calcium absorption in the gut, while calcium and magnesium provide the structural minerals for bone matrix.

Vitamin D Deficiency

• Functions as a hormone regulating calcium absorption—without adequate vitamin D, dietary calcium passes through unabsorbed
• Risk factors: limited sun exposure, darker skin pigmentation, obesity, malabsorption—fat-soluble vitamin gets sequestered in adipose tissue
• Diagnosis via 25-hydroxyvitamin D levels—levels below 20 ng/mL indicate deficiency; 20-29 ng/mL is insufficiency

Calcium Deficiency

• Chronic deficiency causes osteopenia and osteoporosis—the body will leach calcium from bones to maintain critical serum levels
• Acute hypocalcemia presents with tetany, Chvostek's and Trousseau's signs—neuromuscular excitability indicates severe depletion
• High-risk: lactose intolerance, post-menopausal women, chronic corticosteroid use—always assess calcium alongside vitamin D status

Magnesium Deficiency

• Required for over 300 enzymatic reactions—affects muscle contraction, nerve transmission, and cardiac rhythm
• Symptoms include muscle cramps, tremors, and cardiac arrhythmias—hypomagnesemia can cause refractory hypokalemia and hypocalcemia
• Common in alcoholism, diuretic use, and GI diseases—often underdiagnosed because serum levels don't reflect total body stores

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Thyroid & Metabolic Function

Iodine deficiency specifically disrupts thyroid hormone production, creating widespread metabolic consequences. The thyroid gland concentrates iodine to synthesize $T_3$ and $T_4$, which regulate basal metabolic rate.

Iodine Deficiency

• Leading preventable cause of intellectual disability worldwide—fetal and infant brain development requires adequate thyroid hormone
• Classic sign is goiter (enlarged thyroid)—the gland hypertrophies attempting to capture more iodine from circulation
• Rare in countries with iodized salt but common in inland/mountainous regions globally—assess dietary history in immigrant populations

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Immune Function & Tissue Repair

These nutrients support the immune system and maintain tissue integrity. Deficiencies impair wound healing, increase infection susceptibility, and compromise epithelial barriers.

Zinc Deficiency

• Essential for wound healing and immune cell function—deficiency significantly delays surgical recovery and increases infection risk
• Classic symptoms: hair loss, diarrhea, dermatitis, and dysgeusia (altered taste)—the "4 Ds" help you remember
• High-risk: Crohn's disease, chronic diarrhea, vegetarians, elderly—zinc absorption decreases with age and GI inflammation

Vitamin A Deficiency

• Night blindness is the earliest clinical sign—progresses to xerophthalmia (dry eyes) and corneal damage if untreated
• Critical for epithelial cell differentiation and immune function—deficiency increases mortality from measles and diarrheal diseases
• Rare in developed countries but leading cause of preventable childhood blindness globally—assess in refugees and patients from food-insecure regions

Vitamin C Deficiency (Scurvy)

• Required for collagen synthesis—without it, connective tissue breaks down causing bleeding gums, poor wound healing, and joint pain
• Symptoms appear after 1-3 months of severe deficiency—look for perifollicular hemorrhages and corkscrew hairs on exam
• High-risk: food insecurity, alcohol use disorder, restrictive eating, elderly living alone—often a marker of broader nutritional neglect

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Quick Reference Table

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Self-Check Questions

1. A patient presents with fatigue and macrocytic anemia. What two deficiencies should you consider, and what single finding would help you differentiate between them?

2. Which three deficiencies are most critical to assess in a pregnant patient during the first trimester, and why does timing matter for each?

3. Compare the wound healing impairments caused by zinc deficiency versus vitamin C deficiency—what additional symptoms would help you distinguish between them?

4. A patient on long-term proton pump inhibitors presents with numbness in their extremities. Which deficiency is most likely, and what is the mechanism linking PPIs to this condition?

5. You're assessing an elderly patient living alone who eats primarily canned foods and rarely goes outside. Which deficiencies should be highest on your differential, and what clustering of symptoms would you expect?