6.2 Nutritional Disorders
Key Takeaways
- Vitamin B12 and folate both cause macrocytic anemia, but only B12 deficiency produces neurologic disease with elevated methylmalonic acid — giving folate alone to a B12-deficient patient can correct anemia while neuropathy progresses
- In a malnourished or alcoholic patient, administer thiamine before intravenous glucose to prevent precipitating Wernicke encephalopathy
- New-onset iron deficiency anemia in an adult man or postmenopausal woman is occult gastrointestinal blood loss until proven otherwise and warrants referral for GI workup
- Bulimia nervosa patients are usually normal weight or overweight; Russell sign, parotid enlargement, dental erosion, and hypokalemic metabolic alkalosis are the distinguishing clues
- Vitamin B12 neuropathy causes symmetric loss of vibration and position sense with ataxia — a systemic mimic of peripheral neuropathy and radiculopathy that changes chiropractic neurologic assessment
Why Nutritional Disease Matters on Part II
Nutritional questions on NBCE Part II reward pattern recognition: each deficiency has a signature clinical picture, and the boards love pairing two similar syndromes and asking you to split them. Nutrition also overlaps with metabolic syndrome, obesity medicine, and eating disorders — all fair game in General Diagnosis and Associated Clinical Sciences. For chiropractic examinees, nutritional disease often announces itself as fatigue, weakness, neuropathy, bone pain, paresthesias, and gait disturbance — the same language patients use when they seek musculoskeletal care.
Vitamin Deficiencies: The High-Yield Table
| Vitamin | Deficiency Syndrome | Signature Findings |
|---|---|---|
| B12 (cobalamin) | Megaloblastic anemia plus neuropathy | Posterior and lateral spinal column degeneration: loss of vibration and position sense, ataxia, hyperreflexia; elevated methylmalonic acid |
| Folate (B9) | Megaloblastic anemia | Same macrocytic anemia but no neurologic deficits; normal methylmalonic acid; critical in pregnancy (neural tube defects) |
| C (ascorbic acid) | Scurvy | Bleeding gums, perifollicular hemorrhage, corkscrew hairs, poor wound healing |
| D | Rickets (children) / osteomalacia (adults) | Bowing of legs, rachitic rosary in children; diffuse bone pain, Looser zones in adults; low calcium and phosphate with high PTH |
| K | Bleeding diathesis | Elevated PT/INR; antagonized by warfarin; deficiency in newborns and fat malabsorption |
| A | Night blindness, xerophthalmia | Nyctalopia (first sign), Bitot spots, keratomalacia |
| B1 (thiamine) | Beriberi / Wernicke-Korsakoff | Dry beriberi (peripheral neuropathy), wet beriberi (high-output heart failure, edema); Wernicke triad below |
| B3 (niacin) | Pellagra | Dermatitis (photosensitive Casal necklace), diarrhea, dementia — the three Ds |
| B2 (riboflavin) | Ariboflavinosis | Cheilosis, angular stomatitis, glossitis (magenta tongue), photophobia |
The B12 versus Folate Trap
Both cause macrocytic (megaloblastic) anemia with hypersegmented neutrophils. The discriminators the exam tests:
- B12 deficiency causes neurologic disease (subacute combined degeneration of dorsal and lateral columns); folate deficiency does not
- Methylmalonic acid is elevated in B12 deficiency only; homocysteine is elevated in both
- Pernicious anemia (autoimmune destruction of parietal cells and intrinsic factor) is the classic B12 cause — treated with parenteral B12 because oral absorption fails
- Giving folate alone to a B12-deficient patient corrects the anemia while the neuropathy progresses — a classic ethics and safety trap
Thiamine and the Alcoholic Patient
Wernicke encephalopathy equals confusion, ophthalmoplegia (nystagmus, lateral rectus palsy), and ataxia. Untreated, it progresses to Korsakoff psychosis: anterograde amnesia with confabulation. The board-critical rule: in a malnourished or alcoholic patient, give thiamine before intravenous glucose, because glucose load without thiamine can precipitate Wernicke's. Pellagra is also seen in carcinoid syndrome and Hartnup disease.
Iron Deficiency Anemia
The most common anemia worldwide: microcytic, hypochromic red cells with low ferritin, low serum iron, and high total iron-binding capacity (TIBC). Clinical clues include fatigue, pallor, koilonychia (spoon-shaped nails), pica (craving ice or clay), and glossitis. In an adult man or postmenopausal woman, iron deficiency is gastrointestinal blood loss until proven otherwise — think colon cancer and refer for workup. Plummer-Vinson syndrome combines iron deficiency with esophageal webs and dysphagia.
Obesity and Metabolic Syndrome
Body mass index (BMI) equals weight in kilograms divided by height in meters squared. Overweight begins at BMI 25; class I obesity at 30; class III (severe) obesity at 40 or higher. Central adiposity adds risk independent of BMI: waist circumference greater than 40 inches (102 cm) in men or greater than 35 inches (88 cm) in women.
Metabolic syndrome requires any three of five criteria: elevated waist circumference, triglycerides greater than or equal to 150 mg/dL, HDL cholesterol below 40 mg/dL in men or below 50 mg/dL in women, blood pressure greater than or equal to 130/85 mmHg, and fasting glucose greater than or equal to 100 mg/dL. It markedly increases risk of type 2 diabetes and cardiovascular disease; first-line management is lifestyle — weight loss, exercise, and dietary change.
Eating Disorders
- Anorexia nervosa: restriction of intake with intense fear of gaining weight and disturbed body image, leading to significantly low body weight (BMI often below 17). Physical signs include lanugo hair, bradycardia, hypotension, amenorrhea, cold intolerance, and osteoporosis. Refeeding syndrome (hypophosphatemia) is a danger during treatment — refer to appropriate medical care
- Bulimia nervosa: recurrent binge eating with compensatory purging; patients are usually normal weight or overweight — the key contrast with anorexia. Signs include Russell sign (calluses on knuckles from self-induced vomiting), parotid enlargement, dental enamel erosion, and hypokalemic, hypochloremic metabolic alkalosis — the electrolyte abnormality that risks lethal arrhythmia
Protein-Energy Malnutrition
| Feature | Kwashiorkor | Marasmus |
|---|---|---|
| Deficit | Protein (calories relatively adequate) | Total calories (protein plus energy) |
| Edema | Present (pitting, ascites) | Absent |
| Appearance | Flaky-paint dermatosis, depigmented hair, distended abdomen | Severe muscle and fat wasting, skin and bones |
| Liver | Fatty liver (hepatomegaly) | Normal size |
Kwashiorkor's edema reflects low oncotic pressure from hypoalbuminemia; marasmus is simply starvation.
Chiropractic Relevance and Red Flags
Vitamin B12 neuropathy produces symmetric loss of vibration and position sense with ataxia — distinguish from unilateral radiculopathy by symmetry and absence of a dermatomal pattern. Vitamin D deficiency causes osteomalacia with diffuse bone pain and proximal myopathy; fragile bone changes the risk calculus for high-velocity manipulation. Iron deficiency in older adults is a referral red flag for occult malignancy. Eating disorder patients with bradycardia, electrolyte disturbance, or severe weight loss need medical stabilization before aggressive musculoskeletal treatment.
Takeaways: macrocytic anemia with neuropathy equals B12; without neuropathy equals folate; wet beriberi equals heart failure; dry beriberi equals neuropathy; bulimic patients look healthy — hunt for Russell sign and hypokalemic alkalosis; and new iron deficiency in an older adult means occult GI bleeding until proven otherwise.
A 62-year-old vegan woman has macrocytic anemia, hypersegmented neutrophils, loss of vibration sense in both feet, and a wide-based gait. Laboratory testing shows elevated methylmalonic acid. Which treatment mistake would allow her neurologic disease to worsen even as the anemia improves?
An emaciated man with chronic alcohol use is brought to the emergency department confused, with horizontal nystagmus and truncal ataxia. Before any intravenous glucose is administered, which nutrient must be given first?
A 24-year-old college student appears well nourished but reports episodic binge eating followed by self-induced vomiting. Examination shows calluses on the dorsum of the right hand, bilateral parotid enlargement, and eroded dental enamel. Which electrolyte disturbance is most likely?
A 71-year-old man has fatigue, koilonychia, and laboratory confirmation of iron deficiency anemia. He has no history of vegetarian diet or overt bleeding. What is the most appropriate next clinical step?