Minerals Flashcards
What are minerals?
Inorganic elemental atoms that are essential nutrients
Not changed by digestion or metabolism
What are functions of minerals
Participation with enzymes in metabolic processes (cofactors)
Structural functions (Ca, P in bone; S in keratin)
Acid-base and water balance (Na, K, Cl)
Nerve & muscle function (Ca, Na, K)
Unique functions (e.g., heme, B12, thyroid hormones)
Bioavailability and regulation
Absorption
-Small intestine & large intestine
Regulation
-Kidneys & small intestine
minerals in foods
Found in all food groups
More reliably found in animal products
Often other substances in foods decrease absorption (bioavailability) of minerals
Oxalate, found in spinach, prevents absorption of most calcium in spinach.
Phytate, form of phosphorous in most plants makes it poorly available.
Macro/major minerals
Sodium, potassium, magnesium, calcium, phosphorus, sulfur, chloride
Present in body tissues at concentrations >50 mg/kg (50 ppm)
Requirements in g
micro or trace minerals
(body needs relatively less)
Chromium, manganese, iron, cobalt, molybdenum, copper, zinc, fluoride, iodine, selenium, silicon, tin, arsenic, nickel…
Present in body tissues at concentrations <50 mg/kg (50 ppm)
Requirements in mg or µg
factors that affect requirements
Physiological state/level of production Interactions with other minerals Most minerals have an optimal range --Below leads to deficiency symptoms --Above leads to toxicity symptoms Mineral content of soils dictates mineral status of plants
Regulatory functions of calcium
Stimulates blood clotting Muscle contractions Transmission of nerve impulses Vision Regulation of blood glucose Cell differentiation Cofactor for energy metabolism
structural functions of calcium
bones and teeth
Bones
Reservoir to maintain blood calcium
Osteoblasts & osteoclasts
Hydroxyapatite
Large crystal-like molecule
phosphorous
Component of cell membranes & walls
Found in all foods
Structural & functional roles in body
Energy metabolism
functions of phosphorus
Functions Similar to calcium (structure, blood pH) Vitally important in energy metabolism ATP, sugar phosphates Phosphoproteins Impact on environment has scientists revisiting nutritional requirements Reduce P in phytate P form Not as much an issue with ruminants
Metabolism & Regulation of Phosphorus in the Body
Small intestine
Vitamin D-dependent active transport
Simple diffusion
Concentrations controlled by:
Calcitriol, PTH, calcitonin
Potassium
Functions Regulation of osmotic (fluid) and acid-base balance Major cation of intracellular fluid Cofactor for several reactions in carbohydrate metabolism Major salt in ruminant sweat Increases requirement in heat stress Typically high in forages Regulated in kidneys (aldosterone)
sodium
Absolutely an essential nutrient, but has been “demonized” like cholesterol
Typical intakes way higher than what is needed in humans; added to livestock diets
Body usually gets rid of excess quite easily
functions of sodium and chloride
Electrolytes (acid/base balance)
Fluid balance
Nerve function
Muscle contraction
regulation of sodium and chloride in the body
Small intestine Sodium absorbed first Chloride second Sodium Absorbed with glucose Also actively absorbed in colon Water absorption
sulfur
Component of amino acids
Cystine, cysteine, and methionine for bioactive and structural proteins
Wool contains about 4% sulfur
Chondroitin sulfate is a constituent of cartilage
Deficiency is related to protein deficiency
magnesium
Functions Associated with Ca and P 70% of Mg in skeleton Enzyme activation (e.g., pyruvate dehydrogenase) Bioavailability Calcium Phospohorus
metabolism and regulation of magnesium
Stabilizes enzymes Energy metabolism Cofactor for over 300 enzymes DNA & RNA metabolism Nerve & muscle function
bio availability and regulation of trace minerals
Difficult to quantify biochemically
Bioavailability influenced by genetics, nutritional status, nutrient interactions, aging
Absorbed in small intestine
Deficiencies & toxicities rare
Content in plant foods depends on soil content
functions of trace minerals in the body
Cofactors
Metalloenzyme
Components of nonenzymatic molecules
Provide structure to mineralized tissues
iron
Functions Oxygen transport via hemoglobin Needed for ATP production Essential component of many enzymes Immune function Brain function Iron deficiency/toxicity thought to slow mental development in kids
Oxygen transport: hemoglobin
Iron reservoir: myoglobin
Cellular energy metabolism
iron in the body
70% of iron in body is functional; found in enzymes and other molecules
>80% of this found in red blood cells
30% of iron is in storage depots or transport proteins
Iron absorption, transport, storage and loss is highly regulated
oxygen transport
hemoglobin Most abundant protein in red blood cells 4 protein subunits + 4 iron-containing heme groups Delivers oxygen to cells Picks up carbon dioxide
iron resivoir
myoglobin Found in muscle cells Heme group + protein subunit Releases oxygen to cells when needed for: ATP production Muscle contraction
cellular energy metabolism
Cytochromes Heme-containing complexes Function in electron transport chain Allow conversion of ADP to ATP Iron as cofactor Electron transport chain Citric acid cycle Gluconeogensis
iron absorption
Primary regulator of iron homeostasis
1-50% of iron is absorbed.
If body needs more iron, it increases amount of “transferrin” an iron carrying protein.
Iron can also be stored in another protein called “ferritin”
Iron from animal sources much better absorbed than that from plant sources Absorption of iron from plant sources increased by Vitamin C Meat in diet Absorption is decreased by Phytates (grain products) Polyphenols (tea, coffee) Other minerals (calcium, zinc)
Iron Circulation, Uptake Into Cells, & Storage
Transferrin
Delivers iron to body cells
Transferrin receptors
iron storage
Iron storage compounds in liver, bone marrow, and spleen Ferritin Main storage form Hemosiderin Long-term storage
iron dietary sources
Heme iron (high bioavailability) Bound to a heme group Shellfish, beef, poultry, organ meats Makes up Hemoglobin, myoglobin, cytochromes
Nonheme iron (lower bioavailability)
Green leafy vegetables, mushrooms, legumes, enriched grains
~85% of dietary iron
iron supplementation
Haeme > Fe2+ (ferrous) > Fe3+ (ferric)
Ferrous Iron Best absorbed Other terms: Ferrous fumarate, ferrous sulfate, ferrous gluconate Ferric Iron
Absorption, Metabolism, & Regulation of Copper
Absorbed in small intestine & stomach
Influenced by Cu status, decreased by Fe & antacids
Ceruloplasmin
Excess incorporated into bile & eliminated in feces
functions of copper
Cofactor for metalloenzymes in redox reactions: ATP production Cytochrome c oxidase Iron metabolism Neural function Antioxidant function Superoxide dismutase Connective tissue synthesis Stored in most tissues, especially liver
induced copper toxicity
Occurs with “normal” dietary levels of Cu and “low” levels of Mo and S
Accumulates in liver
Sheep are more susceptible than cattle or pigs
iodine
Function Essential component of thyroid hormones Important for regulation of body temperature, basal metabolic rate, reproduction and growth Regulation in body Almost all is absorbed Excess removed in urine
government program: iodine fortification of salt
1920s – “Goiter Belt”
Statewide campaigns
Started providing iodized salt to children
Goiter almost eliminated
Current – Public Health working to eradicate goiter internationally
Absorption, Metabolism, & Regulation of Selenium
Most Se enters blood Incorporated into selenomethionine Makes selenoproteins Stored in muscles Maintenance of Se through excretion in urine
functions of selenium
Catalyzes removal of hydrogen peroxide
Component of glutathione peroxidase
Converts T4 to T3
Improves killing ability of neutrophils
Reduces the prevalence and severity of mastitis
selenium
Antioxidant Shares this role with vitamin E Deficiencies White muscle disease in lambs and calves Skeletal and cardiac myopathies Exudative diathesis (hemorrhagic disease) in chicks
functions of chromium
Regulates insulin Growth & development Lab animals Increases lean mass Decreases fat mass Ergogenic aid Chromium picolinate
Chromium (Cr): Dietary Sources, Bioavailability, & Regulation
Bioavailability affected by: Vitamin C Acidic medications Antacids Transported in blood to liver Excess excreted in urine & feces
functions of manganese
Cofactor for metalloenzymes Gluconeogenesis Bone formation Energy metabolism Cofactor for superoxide dismutase Less than 10% absorbed Incorporated in bile and excreted in faeces
functions of molybdenum
Redox reactions
Cofactor for several enzymes
Metabolism of:
Sulfur-containing amino acids
DNA & RNA
Detoxifying drugs in liver
zinc
Bioavailability influenced by: Phytates Iron Calcium Animal sources Acidic substances
functions of zinc
Cofactor RNA synthesis Stabilizes proteins that regulate gene expression Zinc fingers Antioxidant Stabilizes cell membranes
functions of fluoride
Part of bone & teeth matrix
Stimulates maturation of osteoblasts
Topical application decreases bacteria in mouth
Fewer cavities
fluoride
99% is found in bones and teeth
Function
Promote mineralization of calcium and phosphate
Inhibits bacterial growth in mouthdecreases cavity formation
government program fluoride in water
Drinking water fortified with fluoride
American Dental Association (1-2 ppm)
functions of cobalt
Essential coenzyme for Propionate metabolism methylmalonyl CoA to succinyl CoA DNA synthesis Bacterial synthesis of methionine
cobalt
Known since 1930s that a wasting disease was associated with Co deficiency in plants and soils
Starved for glucose
Vitamin B12 was found to contain Co
cobalt and vitamin B12
Injection of Co-deficient sheep and cattle with Vitamin B12 was as effective as feeding Co in curing the disease
Injection of Co had no effect
Microbial synthesis of Vitamin B12 was the key!
other trace minerals
More research needed about: Nickel Aluminum Silicon Vanadium Arsenic Boron
