(1) bone health and calcium

bone

living tissue that flexes, undergoes constant breakdown and synthesis, and serves as a reservoir for various minerals, contains nerves and cartilage, source of R/WBCs & platelets

periosteum

the thick, fibrous vascular membrane covering most of the cortical bone on the surface of the bone; muscles, tendons, and ligaments connect to the periosteum

cortical bone

provides strength and stability, microscopic openings in cortical bone allow blood vessels and nerves to pass through, which supply nutrients, oxygen, and hormones to bone cells

trabecular bone

found at the end of long bones, provides strength and structural stability, and is a shock absorber

bone marrow

spongy tissue that contains hemopoietic stem cells and stromal stem cells, primarily located in flat bones

hemopoietic stem cells

are capable of developing into blood cells

stromal stem cells

can produce bone, cartilage, and fat

osteoclasts

break down small amounts of bone, breaking down bone is called bone resorption which releases minerals like calcium, phosphorus, and magnesium, into the blood

osteoblasts 

To re-synthesize bone from bone marrow, take up free calcium and phosphorus from the blood and, along with collagen, form hydroxyapatite

hydroxyapatite

adds strength and structure to the bone, calcium main component

bone mineral density

the concentration of minerals found in the bone and is used as an indicator of bone health 

calcium- function

bone growth, maintenance, and repair; muscle and nerve function; blood clotting

calcium- RDA

13-18: 1,300mg; 19+ 1,000mg

calcium- sources

milk, yogurt, cheese, sardines/salmon, kale, broccoli

calcium- bioavalibility

large mineral and not easy to breakdown in the gut, oxalates and phytates bind to calcium and decrease its bioavalibility 

calcium- regulation 

the body tightly regulates blood calcium level regardless of intake

calcitonin

released from the thyroid gland when plasma calcium levels are too high, stimulates bone formation by increasing osteoblastic activity by placing more calcium into the bone and renal excretion of calcium and decreasing calcium absorption in the intestines 

parathyroid hormone (PTH)

released from parathyroid gland when plasma calcium levels are too low, stimulates bone demineralization by increasing the synthesis of calcitriol in the kidney

calcitriol and PTH

increases calcium reabsorption in the kidneys and increases calcium absorption in the intestines

calcium deficiency- osteoporosis

low vitamin D and impaired calcium absorption, bone demineralization may exceed the rate of bone formation, leading to low bone mineral density

other factors associated with osteoporosis

estrogen and testosterone levels- both are protective of bone formation, excessive intake of alcohol and caffeine inhibit bone formation, family history, females, and physical activity

osteoporosis prevention

emphasize maximizing body stores of calcium at an early age and minimizing calcium losses

populations at risk for calcium deficiency

vegans, milk allergy, women over 50, men over 70

calcium toxicity

UL is 2500 mg/day, increase risk of kidney stones, high blood and urinary calcium concentrations, irritability, headache, kidney failure, soft tissue calcification, and decreased absorption of other minerals