Trace Elements in Nutrition

Trace Elements

• Trace elements are inorganic micronutrients found in small quantities.
• Dilute acid washes are used to prevent contamination when handling trace elements.
• Copper (Cu):
  • Most body copper is bound to albumin.
  • Sources include shellfish, nuts, and seeds.
  • Absorbed in the intestines, transported to the liver via the portal vein.
  • Hepatocytes process and package copper into ceruloplasmin, then released into the bloodstream.
  • Functions in iron transport, ATP production, and collagen/elastin support.
  • Normal Range (Adults): 70-140 ug/dL.
  • Menkes Disease: X-linked recessive disorder causing copper deficiency. Low serum copper and ceruloplasmin. Symptoms include floppy muscle tone, kinky hair, seizures, and developmental regression (appears around 2-3 months).
  • Wilson's Disease: Defective copper metabolism leading to copper deposition in tissues. Low serum copper and ceruloplasmin; high tissue copper. Symptoms include liver disease, neurological problems, psychiatric symptoms, and Kayser-Fleischer rings (colored rings around the cornea). Treatment includes chelation therapy for copper removal.
  • Copper Deficiency: Can be seen in adults on long-term intravenous feeding.
• Zinc (Zn):
  • Second most abundant trace element after iron.
  • Stored in muscles, bones, and red blood cells.
  • Sources include red meat and seafood.
  • Absorbed in the intestines. Travels unbound to the liver and binds to proteins (albumin and alpha-2 macroglobulin).
  • Functions in enzyme/protein function, hormone production/activity.
  • Normal Range (Adults): 80-120 ug/dL.
  • Zinc Deficiency: Nonspecific signs include weakened immunity, slow growth, hair loss, and skin lesions.
  • Acrodermatitis Enteropathy: Rare genetic disorder causing zinc deficiency.
  • Diagnosis utilizes atomic absorption spectroscopy, especially for burn patients and those receiving parenteral nutrition. WBCs and platelets provide better tissue zinc measurements when compared to plasma.

Fat-Soluble Vitamins (A, D, E, K)

• Require bile, pancreatic enzymes, and a healthy intestinal lining for absorption.
• Transported by chylomicrons.
• Storage in the liver and fat tissue means depletion occurs more slowly than water-soluble vitamins.
• Factors affecting absorption: Malabsorption syndromes (e.g., Celiac disease, bile/pancreatic diversion), use of olestra, liver disease, premature infants.
• Vitamin A (Retinoids):
  • Includes retinol, retinal, and retinoic acid.
  • Body converts beta-carotene to vitamin A.
  • Sources include orange vegetables (carrots, sweet potatoes).
  • Functions in vision, cell growth, and cancer prevention.
  • Deficiency symptoms: Nyctalopia (night blindness), keratomalacia (severe eye damage).
  • Hypervitaminosis A: Excessive intake, causing nausea/vomiting, liver damage, and increased intracranial pressure. Can cause birth defects if ingested during pregnancy.
  • Inflammation: May decrease retinol-binding protein and transthyretin, causing false low vitamin A readings. Inflammation markers include CRP, serum albumin and ferritin.
• Vitamin D:
  • Crucial for bone health and calcium regulation.
  • Vitamin D2: Found in plants and fortified foods.
  • Vitamin D3: Synthesized in skin upon sun exposure, more effective.
  • 25(OH)D: Main marker for vitamin D; reflects long-term levels.
  • Deficiency symptoms: Rickets, osteomalacia, osteoporosis.
• Vitamin E (Tocopherols and Tocotrienols):
  • Protects red blood cells, supports neurological/reproductive health.
  • Sources include nuts and seeds.
  • Deficiency symptoms: Edema, hemolytic anemia, fat malabsorption.
• Vitamin K (Phylloquinone and Menaquinone):
  • Essential for blood clotting (prothrombin).
  • K1: Plant-based foods (leafy greens), used to treat premature infants.
  • K2: Fermented foods (cheese, eggs).
  • Deficiency symptoms: Increased bleeding (ecchymosis, epistaxis).

Water-Soluble Vitamins (B, C)

• Not stored in large amounts, requiring regular intake.
• Vitamin C (Ascorbic Acid):
  • Antioxidant, maintains iron and copper in reduced states, cofactor.
  • Sources include citrus fruits.
  • Absorbed actively in the GI tract.
  • Deficiency symptoms: Scurvy (bleeding gums, joint pain, poor wound healing.)
  • Hypervitaminosis C: GI discomfort, kidney stones, increased uric acid excretion.
• Vitamin B12 (Cobalamin):
  • Essential for erythrocyte maturation, homocysteine metabolism.
  • Sources include animal products.
  • Absorption involves haptocorrin, intrinsic factor, and transcobalamin II.
  • Deficiency symptoms: Pernicious anemia (autoimmune destruction of parietal cells and intrinsic factors), hyper-segmented neutrophils, macrocytosis, megaloblastic anemia.
  • Testing: Schilling test for absorption.
• Vitamin B3 (Niacin):
  • Component of NAD and NADP, involved in redox reactions.
  • Sources include meat.
  • Deficiency symptoms: Pellagra (dermatitis, diarrhea, dementia).
• Folic Acid:
  • Transfers one-carbon groups in metabolic reactions.
  • Sources include dark leafy greens.
  • Deficiency symptoms: Megaloblastic anemia, neural tube defects in pregnancy. MTHFR gene mutation can cause issues.

Endocrine System and Other Topics

(See separate sections below for summaries of these broader categories.)