3.4 Trace Minerals

Trace minerals play crucial roles in our bodies, from supporting immune function to regulating metabolism. While needed in small amounts, these nutrients are essential for optimal health. Iron, zinc, copper, and selenium are just a few examples of trace minerals with vital functions.

Absorption of trace minerals occurs mainly in the small intestine through various mechanisms. Dietary sources and factors affecting absorption vary for each mineral. Deficiencies can lead to health issues, while toxicities may occur with excessive intake. Understanding these aspects is key to maintaining proper mineral balance.

Trace Minerals: Roles, Absorption, and Health Implications

Essential trace minerals and roles

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• Iron enables oxygen transport via hemoglobin, supports muscle function through myoglobin, and facilitates energy metabolism (ATP production)
• Zinc bolsters immune system, accelerates wound healing, and maintains sense of taste and smell (gustatory and olfactory functions)
• Copper aids iron metabolism, forms part of antioxidant enzymes (superoxide dismutase), and promotes collagen synthesis for skin and connective tissues
• Selenium acts as powerful antioxidant, supports thyroid hormone production, and enhances immune response (T-cell function)
• Iodine crucial for thyroid hormone synthesis, regulates metabolic rate, and ensures proper fetal brain development (neurogenesis)
• Manganese serves as cofactor for numerous enzymes, contributes to bone formation (osteoblast function), and assists in metabolism of macronutrients
• Fluoride strengthens tooth enamel, increases bone density, and prevents dental decay (remineralization)
• Chromium enhances insulin sensitivity, helps regulate blood glucose levels, and supports macronutrient metabolism
• Molybdenum acts as cofactor for enzymes involved in sulfur amino acid metabolism and uric acid production

Absorption and transport of trace minerals

• Absorption mechanisms
  • Active transport moves minerals against concentration gradient (requires energy)
  • Passive diffusion allows minerals to move along concentration gradient (no energy needed)
  • Facilitated diffusion uses carrier proteins to enhance mineral movement (no energy required)
• Absorption sites
  • Small intestine serves as primary absorption location (duodenum and jejunum)
  • Stomach provides limited absorption for some minerals (iron)
• Factors affecting absorption
  • Intestinal pH influences mineral solubility and absorption efficiency
  • Mineral interactions can enhance or inhibit absorption (iron-zinc competition)
  • Dietary components impact bioavailability (phytates reduce zinc absorption)
• Transport in blood
  • Specific protein carriers shuttle minerals (transferrin for iron, ceruloplasmin for copper)
  • Albumin binds and transports various minerals non-specifically
  • Some minerals circulate as free ions in plasma
• Storage and distribution
  • Liver acts as primary storage organ for many trace minerals (iron in ferritin)
  • Bones store certain minerals for long-term use (fluoride in hydroxyapatite)
  • Specific tissues concentrate certain minerals (iodine in thyroid gland)

Dietary sources and absorption factors

• Iron sources
  • Heme iron found in animal products offers high bioavailability (red meat, poultry, fish)
  • Non-heme iron present in plant foods with lower absorption rate (lentils, spinach, fortified cereals)
• Zinc sources include oysters, beef, poultry, dairy products, and whole grains (wheat germ)
• Copper abundant in shellfish, nuts, seeds, whole grains, and dark chocolate
• Selenium rich foods include Brazil nuts, fish (tuna), poultry, and whole grains
• Iodine sources comprise iodized salt, seafood (seaweed), dairy products, and eggs
• Factors influencing absorption
  • Enhancers
    1. Vitamin C boosts iron absorption (citrus fruits with iron-rich meals)
    2. Animal protein improves zinc and iron uptake (meat factor)
  • Inhibitors
    1. Phytates in whole grains and legumes bind minerals, reducing absorption
    2. Tannins in tea and coffee interfere with iron absorption
    3. Calcium can hinder iron absorption when consumed together
  • Cooking methods affect mineral content and bioavailability (boiling can leach minerals)
  • Soil composition influences mineral levels in plant-based foods (selenium content varies by region)

Deficiencies and toxicities of trace minerals

• Iron
  • Deficiency leads to anemia, fatigue, and impaired cognitive function (poor concentration)
  • Toxicity can cause liver damage and increase risk of cardiovascular disease (hemochromatosis)
• Zinc
  • Deficiency impairs immune function, delays wound healing, and causes loss of taste (hypogeusia)
  • Toxicity induces nausea, vomiting, and interferes with copper absorption
• Copper
  • Deficiency results in anemia, neutropenia, and increased risk of osteoporosis
  • Toxicity damages liver and causes neurological symptoms (Wilson's disease)
• Selenium
  • Deficiency weakens immune system and may increase cancer risk
  • Toxicity causes hair loss, nail brittleness, and neurological problems (selenosis)
• Iodine
  • Deficiency leads to goiter, hypothyroidism, and impaired fetal development (cretinism)
  • Toxicity disrupts thyroid function and can paradoxically cause goiter
• Manganese
  • Deficiency impairs growth and causes skeletal abnormalities
  • Toxicity manifests as neurological symptoms resembling Parkinson's disease
• Fluoride
  • Deficiency increases risk of dental caries and may weaken bone structure
  • Toxicity causes dental fluorosis (mottled teeth) and skeletal fluorosis (bone pain)
• Chromium
  • Deficiency impairs glucose tolerance and increases cardiovascular risk
  • Toxicity rare but can damage liver and kidneys (occupational exposure)
• Molybdenum
  • Deficiency rarely occurs but can lead to neurological symptoms
  • Toxicity produces gout-like symptoms and anemia (excessive supplementation)