4. Micronutrients

 

 

Calcium and Vitamin D in Gastrointestinal Disorders

  • Calcium and Vitamin D Absorption:
    • Vitamin D is critical for calcium absorption in the proximal small intestine, enhancing intestinal calcium transport by regulating active transport mechanisms (Bischoff et al., 2020).
    • Vitamin D deficiency can lead to hypocalcemia due to reduced intestinal calcium absorption and secondary hyperparathyroidism, potentially leading to osteomalacia or rickets.
    • In cases of small bowel disease or resection, the colon may play a compensatory role in calcium absorption in the absence of sufficient small intestinal absorption.

  • Impact of Proton Pump Inhibitors (PPIs):
    • PPIs may cause hypomagnesemia, impairing the parathyroid gland's response to hypocalcemia and contributing to secondary issues in calcium metabolism (Candido et al., 2022).

Vitamin D Deficiency and Associated Conditions:

  • Primary Hyperparathyroidism (PHPTHism): Vitamin D deficiency is frequently observed in PHPTHism, exacerbating calcium dysregulation (Kvammen et al., 2020).
  • Causes of Deficiency:
    • Inflammatory bowel diseases (e.g., Crohn's disease) leading to malabsorption.
    • Long-term parenteral nutrition without adequate supplementation.
    • Post-bariatric surgery due to reduced absorptive surface.

Zinc Deficiency:

  • Causes: Seen in conditions such as Crohn’s disease, severe chronic liver disease, and cystic fibrosis (Arvanitakis et al., 2020).
  • Symptoms:
    • Acrodermatitis (scaly erythematous rash on extensor surfaces and peri-oral/perianal regions).
    • Dysgeusia (altered taste perception), immune dysfunction, alopecia, leukonychia, and diarrhea.

Vitamin E Deficiency:

  • Clinical Manifestations: Hemolytic anemia and neurological symptoms, such as ataxia and peripheral neuropathy.

Vitamin B12 Deficiency:

  • Sources: Found primarily in animal products (e.g., fish, meat, eggs, and dairy); fortified cereals may provide alternative sources for vegetarians.
  • Absorption Mechanism:
    • In the stomach, pepsin releases cobalamin from dietary proteins, which binds to R-proteins.
    • In the duodenum, pancreatic enzymes cleave the R-cobalamin complex, allowing cobalamin to bind to intrinsic factor (IF).
    • This cobalamin-IF complex is absorbed in the ileum through ATP-dependent processes.
  • Causes of Deficiency:
    • Autoimmune conditions (e.g., pernicious anemia with anti-parietal cell antibodies).
    • Gastrectomy or bariatric surgery (due to loss of IF production).
    • Ileal resection (as in Crohn’s disease) impairs B12 absorption.
    • Chronic use of PPIs or H2 receptor antagonists, which reduce gastric acid and pepsin secretion.
    • Small intestinal bacterial overgrowth (SIBO) can also lead to impaired absorption due to bacterial binding of B12.

Prevention and Management:

  • Nutritional Support:
    • Adequate supplementation of calcium and vitamin D, especially in patients on long-term parenteral nutrition (Lochs et al., 2006).
    • Proactive monitoring of vitamin and mineral levels in at-risk patients.
  • Preventing B12 Deficiency:
    • Early supplementation in high-risk groups (e.g., post-surgical patients, strict vegans).
    • Use of hydroxocobalamin or cyanocobalamin for replacement therapy.

References:

  1. ESPEN Clinical Nutrition Guidelines
  2. Clinical Nutrition in IBD
  3. Clinical Nutrition ESPEN Journal