Minerals: Classification, Deficiencies, and More

Minerals Overview

• Minerals make up a small fraction of total body weight (4-5%), but are essential for human metabolism.
• Minerals cannot be synthesized by the body and must be supplied through dietary intake, similar to vitamins.

Deficiencies and Excesses

• Most minerals require an optimal range for health.
• Being below this range can lead to deficiency symptoms.
• Being above this range can lead to toxicity symptoms.
• Mineral deficiencies or excesses can take months to develop, as they depend on the body's mineral stores.

Mineral Classification

• Macro/Major Minerals (7): Present in body tissues at concentrations greater than 50 mg/kg (50 ppm).
  • Includes calcium, phosphorus, potassium, sodium, chloride, sulfur, and magnesium.
• Micro/Minor or Trace Minerals (11): Present in body tissues at concentrations less than 50 mg/kg (50 ppm).
• Includes iron, zinc, copper, molybdenum, selenium, iodine, manganese, cobalt, fluoride, chromium, and boron.

Nutritionally Important Minerals

• Calcium (Ca): 15 g/kg
• Phosphorus (P): 10 g/kg
• Potassium (K): 2 g/kg
• Sodium (Na): 1.6 g/kg
• Chlorine (Cl): 1.1 g/kg
• Sulfur (S): 1.5 g/kg
• Magnesium (Mg): 0.4 g/kg
• Iron (Fe): 20-50 mg/kg
• Zinc (Zn): 10-50 mg/kg
• Copper (Cu): 1-5 mg/kg
• Molybdenum (Mo): 1-4 mg/kg
• Selenium (Se): 1-2 mg/kg
• Iodine (I): 0.3-0.6 mg/kg
• Manganese (Mn): 0.2-0.5 mg/kg
• Cobalt (Co): 0.02-0.1 mg/kg

Macrominerals

• Macrominerals are required in amounts of ≥100 mg/day.
• The 7 macrominerals are sodium, phosphorus, calcium, sulfur, chloride, potassium, and magnesium.

Macrominerals - Bioavailability & Regulation

• Bioavailability: Influenced by genetics, aging, nutritional status, and other compounds in food.
• Oxalate, found in spinach, prevents absorption of most calcium in spinach.
• Phytates (salts of phytic acid) in plants form complexes with dietary minerals like iron and zinc, causing mineral-related deficiency.
• Phosphorus in phytates is not utilized by humans because they lack the enzyme phytase.
• Regulation of macrominerals occurs in the kidneys & small intestine.

Functions of Macrominerals

• Building bones.
• Maintaining body fluid homeostasis.
• Maintaining optimum pH in body tissues.
• Transmitting nerve impulses.
• Maintaining cell membrane structures.
• Facilitating enzyme action.

Sodium

• Daily intakes are typically higher than what adults need.
• Blood levels are regulated by aldosterone, which increases renal reabsorption of sodium in the kidneys.
• Functions of sodium:
• Contribute to the osmotic balance of body fluids.
• Major cation of extracellular fluid.
• Nerve transmission.
• Transport and absorption of sugars and amino acids.
• Dietary sources:
• Table salt.
• Monosodium glutamate (MSG).
• Highly processed foods.
• Some meats, dairy products, poultry, and seafood.
• Bioavailability: Affected by malabsorption.
• High blood sodium (hypernatremia) linked to high blood pressure and heart disease.
• High blood sodium is rarely due to dietary excess, but more often to other factors like genetics and exercise.

Regulation of Blood Sodium by Aldosterone

• Decreased aldosterone secretion by the adrenal glands leads to increased sodium excretion in the urine.
• Low aldosterone levels favor increased sodium excretion in the urine.
• Aldosterone stimulates decreased sodium excretion in the urine.
• Increased aldosterone secretion by the adrenal glands leads to decreased sodium excretion in the urine.

Chloride

• Important for acid-base and osmotic regulation of fluid balance.
• Integral to HCl and chloride salts in gastric secretions.
• Removal of carbon dioxide from tissues to lungs via chloride shift.
• Essential component of immune function (recruitment and activation of immune cells).

Chloride Shift

• Chloride shift facilitates the transport of carbon dioxide from tissues to the lungs.
• It involves the antiport of bicarbonate and chloride in red blood cells.

Sodium & Chloride

• Commonly found together in foods.
• Join via ionic bonds to form salt.
• Added freely to foods during processing, cooking, or eating.
• Absorbed in the small intestine with sodium absorbed first (with glucose, also actively absorbed in colon - water absorption) and chloride absorbed second.

Sodium & Chloride Deficiencies

• Infants & children: Can occur due to diarrhea and vomiting.
• Athletes: Potential for deficiency during endurance sports.
• Symptoms of deficiency: Nausea, dizziness, muscle cramps, and coma.

Sulfur

• Component of the amino acids cystine, cysteine, and methionine.
• Chondroitin sulfate is a constituent of cartilage.
• Deficiency is related to protein deficiency.

Magnesium

• Sources: Green leafy vegetables, seafood, legumes, nuts, dairy products, chocolate, brown rice, whole grains.
• Bioavailability:
• Calcium competes with magnesium for binding sites on proteins and membranes; excessive calcium intake decreases magnesium absorption.
• Phosphorus forms chelates with magnesium, decreasing magnesium absorption.

Magnesium Functions

• Associated with calcium and phosphorus: 70% of magnesium is in the skeleton.
• Enzyme activation: Acts as a cofactor for over 300 enzymes involved in energy metabolism including Na/K-ATPase.
• DNA & RNA metabolism.
• Nerve & muscle function: Blocks neurosynaptic transmission by interfering with the release of acetylcholine (affects smooth muscle contraction and muscular relaxation).
• Helps in relieving anxiety and stress.
• Essential cofactor for the synthesis and salvage of purine and pyrimidine nucleotides.
• Plays integral roles in the structure of nucleic acids, affecting their interaction with proteins and ligands.
• Required for DNA replication, transcription into RNA, and translation into protein.
• Hypomagnesemic tetany is also associated with increased neuronal excitability, usually associated with hypocalcemia and involuntary muscle contraction.
• Magnesium is necessary for parathormone secretion.
• Low levels of magnesium (hypomagnesemia) lead to decreased parathormone secretion, resulting in hypocalcemia.

Magnesium Deficiency

• Known as Hypokalemia
• Alcoholics (reduced intake, decreased absorption, or increased urinary excretion).
• Results in abnormal nerve & muscle function (neurological symptoms and muscle cramps).
• Increase risk for CVD and hypertension & type 2 diabetes
• Linked to anxiety and stress, attention deficit disorder.

Magnesium Toxicity

• Typically happens with large dose supplements.
• Symptoms include diarrhea, loss of appetite.
• Causes muscle weakness.
• Causes irregular heartbeats and low blood pressure.
• Difficulty breathing can occur.
• Changes in mental state.

Potassium

• Absorption in small intestine & colon.
• Regulated by kidneys and aldosterone (increases excretion).
• Functions:
  • Regulation of osmotic & acid-base balance.
  • Major cation of intracellular fluid.
  • Enhances nerve and muscle excitability: causes muscle relaxation.
  • Contributes to blood pressure control by relaxing the walls of the blood vessels, lowering blood pressure.
  • Acts as Cofactor for several enzymes involved in carbohydrate metabolism (pyruvate kinase).

Potassium Deficiency (Hypokalemia)

• Due to: Diarrhea & vomiting, overuse of diuretics.
• Results in muscle weakness, constipation, irritability, confusion, insulin resistance, irregular heart function, increased blood pressure, and difficulty breathing.

Iron

• Most common nutrient deficiency in the world.
• Functions:
• Oxygen transport via hemoglobin (necessary for ATP production!).
• Found in the structure of myoglobin: Releases O₂ to cells when needed for ATP production & muscle contraction.
• Cellular energy metabolism (oxidative phosphorylation at the mitochondria).
• Cytochromes - heme containing complexes that function in the electron transport chain, allow the conversion of ADP to ATP.
• Cofactor - Found in the electron transport chain, citric acid cycle, gluconeogenesis, antioxidant enzymes, CYP 450.
• Immune function (T lymphocyte-dependent cellular immunity and intracellular microbial killing by polymorphonuclear leukocytes).
• Brain function (Iron deficiency/toxicity slows mental development in young children).

Iron in the Body

• 70% of iron in the body is functional, found in enzymes and other molecules (80% of this is found in red blood cells).
• 30% of iron is in storage depots or transport proteins.
• Iron absorption, transport, storage, and loss are highly regulated.
• Absorption of iron from plant sources increases with vitamin C & meat in the diet.
• Absorption is decreased by phytates (grain products), polyphenols (tea, coffee), and some minerals (calcium, zinc).
• Exfoliation of intestinal mucosal cells is how iron is primarily lost into stool.
• Minute amounts are removed through bile, urine, and perspiration (about 1 mg/day).
• The main regulator of iron homeostasis is iron absorption.
• The body can absorb between 1% and 50% of iron
• Increases the amount of "transferrin,",if the body requires more iron.
• Iron also is stored with ferritin as well.

Effect of Iron Status on Iron Absorption

• Iron deficiency:
  • Increases production of transport proteins (transferrin).
  • Decreases ferritin production.
• Adequate or excess iron:
  • Decreases production of transport proteins.

Iron Storage

• Iron is stored as Ferritin (main storage form) and Hemosiderin (long-term storage).

Iron Deficiency Anemia

• Public health concern around the world.
• Infants, children, pregnant and lactating women most at risk.
• Symptoms and laboratory findings:
  • Decreased hemoglobin concentration of blood.
  • Decreased red blood cell size.
  • Decreased ferritin.
  • Increased transferrin.
• Cognitive problems, poor growth, decreased exercise tolerance.

Copper

• Sources: Organ meats, dark chocolate, dried apricots, shellfish, whole-grain products, mushrooms, nuts, and legumes.
• Bioavailability decreases with antacids & iron.
• Functions:
  • Cofactor for metalloenzymes in redox reactions.
  • ATP production, specifically Cytochrome c oxidase.
  • Iron metabolism.
  • Neural function.
  • Antioxidant function (Superoxide dismutase).
  • Connective tissue synthesis (impaired collagen and elastin formation, cofactor for lysyl oxidase).
• Deficiency: Anemia, hair loss, bone disorders, central nervous lesions with muscular incoordination.
• Hospitalized patients & preterm infants are more suseptible.
• Antacids.
• Signs & Symptoms: Defective connective tissue, anemia, and neural problems.
• Toxicity is rare.

Selenium

• Makes selenoproteins (glutathione peroxidase and thioredoxin reductase).
• Stored in muscles.
• glutathione peroxidase catalyzes the removal of hydrogen peroxide.
• Protects cells from autooxidative damage, shares this role with vitamin E.
• Component of iodothyronine- 5'- deiodinase that converts T4 to T3.
• Improves the killing ability of neutrophils.

Chromium

• Food content is dependent on soil composition.
• Found in whole grains, fruits/veg, processed meats, beer, and wine.
• Essential element involved in the regulation of blood glucose levels.
• Reduces insulin resistance (activates insulin receptor).
• In lab animals, it increases lean mass & decreases fat mass.

Manganese

• Functions:
• Cofactor for metalloenzymes.
• Gluconeogenesis.
• Bone formation.
• Energy metabolism.
• Cofactor for superoxide dismutase (MnSOD).

Zinc

• Sources: Lamb and beef, pumpkin seeds and oil, chickpeas, cocoa powder, cashews, kefir or yogurt, mushrooms, spinach, chicken.
• Absorption inhibited by phytates, iron, and calcium.
• Functions:
  • As a cofactor for SOD (Cu,Zn-superoxide dismutase).
  • Stabilizes proteins that regulate gene expression (Zinc fingers).
  • As an antioxidant.
  • Stabilizes cell membranes.
  • Contributes to immune function.
• Zinc is vital for: A healthy immune system, DNA synthesis, healthy growth during childhood, healing wounds, and male fertility.
• It Activates T lymphocytes (T cells).
• Zinc deficiency can severely impair immune system function.
• Poor zinc intake increases the risk factor for low quality of sperm and male infertility.

Fluoride

• 99% is found in bones and teeth.
• Functions:
• Promotes mineralization of calcium and phosphate.
• Topical application decreases bacteria in mouth, inhibits bacterial growth, and decreases cavity formation.
• The American Dental Association recommends water fluoridation at 1ppm.
• Very common, dental fluorosis is caused by hypomineralization of tooth enamel caused by ingestion of excessive fluoride during enamel formation in childhood.
• Teeth with dental fluorosis become resistant to dental caries (tooth decay caused by bacteria).

Cobalt

• Found in the structure of Vitamin B12 (cyanocobalamin).
• Essential coenzyme for:
  • Propionate metabolism.
  • DNA synthesis.
  • Bacterial synthesis of methionine.