Trace Minerals & Bioavailability Chapter 7

Vocabulary flashcards covering core concepts from trace minerals, iron and iodine metabolism, zinc/copper interactions, and body water balance.

Bioavailability

Proportion of an ingested nutrient absorbed and usable by the body; influenced by plant binding substances, gastric acidity, chemical form, meal composition, and body need.

Trace minerals

Nine minerals required in small amounts in the body (Fe, I, Zn, Cu, Mn, Cr, Se, Mo, F) with defined roles and dietary requirements.

Heme iron

Iron found in meat, fish, and poultry; absorbed more readily than nonheme iron.

Nonheme iron

Iron found in plant and animal tissues; absorbed less efficiently than heme iron.

Ferric iron (Fe3+)

Iron form that must be reduced to the ferrous form (Fe2+) for absorption.

Ferrous iron (Fe2+)

Soluble iron form that is readily absorbed in the small intestine.

Gastric acid

Stomach acid that helps reduce Fe3+ to Fe2+ to aid iron absorption.

Ascorbic acid (Vitamin C)

Enhances iron absorption, especially nonheme iron, by reducing ferric to ferrous iron and improving solubility.

Phytates

Plant compounds that bind minerals and reduce absorption (notably iron and zinc).

Oxalates

Plant compounds that can bind minerals and hinder absorption.

Factors favoring iron absorption

Body need, presence of ascorbic acid, and an acidic environment that promote Fe2+ formation and uptake.

Factors hindering iron absorption

Binding agents (phytates/oxalates), low gastric acid, infection, GI disease, and high calcium intake.

Iron deficiency anemia

Hypochromic, microcytic anemia caused by insufficient iron; a widespread global issue.

RDI for iron

14 mg/d for men; 33 mg/d for premenopausal women; 26 mg/d for adolescent girls.

Iodine

Essential component of thyroid hormones (thyroxine) produced in the thyroid and required for metabolism.

Thyroxine (T4)

Thyroid hormone (produced in the thyroid) that regulates metabolism and basal metabolic rate.

TSH (thyroid-stimulating hormone)

Stimulates iodine uptake by thyroid cells and regulates thyroid hormone production.

Iodine deficiency disorder

Goiter: visible enlargement of the thyroid from iodine deficiency.

Goiter

Enlargement of the thyroid gland due to insufficient iodine or impaired hormone production.

Cretinism

Severe iodine deficiency during brain development causing irreversible mental retardation.

Iodine RDA

150 mcg/d for adults; 220 mcg/d during pregnancy; 290 mcg/d during lactation.

Iodized salt

Table salt fortified with iodine (about 1 mg iodine per 10 g of salt).

Fluoride

Mineral that protects bones and teeth; AI is 4 mg/d for men and 3 mg/d for women; excess can cause dental fluorosis.

Fluoride toxicity

Excess intake (>10 mg/d for >10 years) can lead to pitting and discolored teeth.

Copper

Trace mineral involved in energy production and hemoglobin synthesis; RDA 0.9 mg/d; rich in liver, seafood, nuts, seeds; zinc can reduce copper bioavailability.

Zinc

Essential trace mineral involved in 100+ enzymes; growth; absorbed poorly with phytates; RDA 11 mg/d (men), 8 mg/d (women); UL 40 mg; absorption inhibited by phytates and iron supplements.

Zinc deficiency symptoms

Hypogonadism; loss of taste and smell; impaired wound healing; impaired growth; malabsorption; weakened immunity.

Zinc interactions

Zinc supplements can interfere with iron and copper absorption; iron supplements can interfere with zinc absorption.

Manganese (Mn)

Trace mineral (~20 mg total body); RDA 2.3 mg/d (men), 1.8 mg/d (women); stored in liver, bones, pancreas, and pituitary; involved in enzymes.

Chromium

Trace mineral that enhances insulin activity and glucose uptake; AI 35 µg/d (men), 25 µg/d (women, 19–50); 30 µg/d (men, 50+).

Selenium

Trace mineral in antioxidant enzymes; vitamin E sparing; AI/RDA ~55 µg/d; abundant in seafood, legumes, whole grains, lean meats, dairy.

Molybdenum

Enzyme cofactor; AI ~45 µg/d.

Water distribution (body)

Women ~50–55% and men ~55–60% of body weight as water; men typically have more muscle mass and higher water content.

Functions of water

Provides structure, acts as solvent, enables chemical reactions, transports nutrients and wastes, regulates temperature, cushions joints, and protects tissues.

Water compartments

Extracellular fluid (ECF) outside cells; intracellular fluid (ICF) inside cells; ECF includes plasma and interstitial fluid.

Capillary fluid shift mechanism

Movement of water between capillaries and tissues driven by hydrostatic pressure and colloid osmotic pressure.

Albumin/globulin

Plasma proteins that influence water movement and help maintain blood volume.

ADH (antidiuretic hormone, vasopressin)

Hormone that increases kidney water reabsorption; rises with dehydration or blood loss.

Aldosterone

Sodium-conserving hormone that promotes Na and water reabsorption; part of the renin-angiotensin-aldosterone system.

Electrolytes

Minerals that dissociate into ions; measured in milliequivalents (mEq); Na is the main extracellular cation; K is the main intracellular cation.

Osmosis

Movement of water across membranes toward higher solute concentration.

Capillary pressure balance

Hydrostatic pressure vs colloid osmotic pressure control water and solute movement across capillary walls.

Thirst and hydration AI for fluids

AI for total water intake is about 13 cups/day for men and 9 cups/day for women; minimum ~4 cups; varies with activity and environment.

Bioavailability note

Bioavailability can be limited by factors like phytates affecting calcium, zinc, and iron absorption.

DRI expressions

Minerals are expressed as RDA, EAR, or AI; ULs are established to prevent toxicity.

Major vs trace minerals (definition)

Major minerals (>100 mg/d); trace minerals (<100 mg/d or <0.01% body weight).