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Lecture

Kin110_Chapter 8 Major & Trace Minerals.docx

6 Pages
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Department
Biomedical Physio & Kines
Course Code
BPK 110
Professor
Gina Whitaker

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Kin110 Chapter 8 Major & Trace Minerals Bone Protein matrix, mostly collagen Hardened by minerals mostly calcium, phosphorus, also magnesium, sodium, fluoride, other minerals Requires -protein and vitamin C to maintain collagen -calcium and other minerals to ensure solidity -vitamin D to maintain calcium and phosphorus levels Bone Remodelling Bone is always remodelling-breaking down and building up When blood Ca2+ levels are low, cells called osteoclasts promote bone resorption (break down of bone to release Ca2+) When blood Ca2+ levels are high, cells called osteoblasts promote bone formation Bone resporption vs. bone re-absorption Bone formation > Bone resporption = net building bone Bone resorption > bone formation = net bone loss Peak Bone Mass-the maximum bone density attained at any time in life Until ≈ age 30, you have a limited time to build up bone mass. After that it declines for everyone -especially women, especially after menopause due to drop in estrogen Weight-bearing activity, calcium, vitamin D important to prevent osteoporosis Osteoporosis-a bone disorder characterized by reduced bone mass More bone loss than formation Results in fractures Risks associated with level of peak bone mass and rate at which bone is lost -affected by genetics, gender, age, hormones, low body weight, and lifestyle (smoking, alcohol, exercise, diet) Calcium distribution in the body Most of the Ca2+ in the body (99%) stored in bone -hydroxyapatite crystals: Ca10(PO4)6(OH)2 Remaining 1% Circulating in blood but levels are tightly regulated Intracellular stores and uses -muscle contraction (includes vasoconstriction) -cell signaling and communication -cofactor -blood pressure regulation Blood Ca2+ Regulation Drop in blood calcium levels increases parathyroid hormone release, which stimulates -bone resorption-increased osteoclast activity to release Ca2+ from bone -Ca2+ re-absorption at the kidneys -activity of Vitamin D Increase in blood calcium levels increases calcitonin release -inhibits bone resorption Calcium Intake & Sources Adults 19-50 yrs old need 1000mg/day Adults > 50 need 1200mg/day Most abundant in milk & other dairy products Non-dairy sources include -cauliflower, bok choy, broccoli, spinach -almonds -fortified soy products -canned fish with bone -bone soup stock Bioavailability & Handling Enhanced Absorption -vitamin D -lactose, fat -acidic foods -growth Hormone Enhanced Excretion -high protein intake -excessive caffeine or alcohol -smoking Inhibit Absorption -oxalates, phytates -high phosphorus or magnesium intake -high fiber diet -low estrogen levels ≥ 50% absorbed -cauliflower, watercress, Chinese cabbage, brussel sprouts, rutabaga, kohlrabi, kale, mustard greens, bok choy, broccoli, turnip greens, Ca-fortified foods & beverages ≈ 30% absorbed -milk, Ca-fortified soy milk, tofu, cheese, yogurt ≈ 20% absorbed -almonds, sesame seeds, pinto beans, sweet potato ≤ 5% absorbed -spinach, rhubarb, Swiss chard Deficiency Low calcium intake -during growth: prevents bone from reaching optimal mass and density -after optimal bone mass is reached, bone resorption > bone formation (blood Ca concentration are maintained at the expense of bones) Low blood calcium results in hypocalcemia -not a result of low calcium intake -causes include kidney failure, parathyroid disorders, Vitamin D deficiency -may lead to muscle spasms, convulsions Toxicity High blood calcium results in hypercalcemia -not caused by excessive intake -primary causes include cancer, overproduction of Parathyroid hormone, excess Vitamin D -effects include fatigue, constipation, kidney stones, confusion, tissue calcification Excess calcium also interferes with absorption of other minerals -iron, magnesium, zinc Upper limit is set at 2500mg/day however; it depends on absorption Phosphorus Most found in complex with calcium in bone and teeth -hydroxyapatite crystals Ca10(PO4)6(OH)2 Also involved in many cellular activities -regulates pH inside a cell -forms part of DNA, RNA, phospholipids, some proteins, ATP -important in activation/deactivation of enzymes RDA 700mg/day Food sources include dairy products, meat, cereals, bran, eggs, nuts, fish Deficiency & Toxicity are rare Deficiency can cause bone loss, weakness, loss of appetite Note: kidneys help regulate phosphorus levels to ensure optimal ratio with calcium for bone m
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