Chapter 13: Bone Health

What are bones made of?

• Mineral Crystals

  • provide strength and support

• Protein

  • provide flexibility

What is bone health defined by?

• bone mineral density

  • how tight the crystals are packed in the protein

How do bones grow?

• Broken down by osteoclasts and rebuilt by osteoblasts

• Grow in teenage years and then remodeling occurs

• osteoclasts remain active, osteoblasts reduce overtime, leading to bone loss

What factors affect bone health?

– Genetics
– Weight-bearing activity
– Consumption of alcohol and animal protein
– Smoking
– Adequate nutrient intake
– Sleep
– Stress
– Body weight

Collagen is supported by…

• protein

• vit c

Mineral crystals are supported by…

– Calcium
– Phosphorus
– Magnesium
– Fluoride
– Vitamin D
– Vitamin K

What are calcium’s functions in bones?

• Integral part of bones, together with phosphorus

• Bones serve as a bank to release calcium to body fluids with decrease in blood concentration

• Formation & dissolution of bone minerals in constant flux
  ■ Hydroxyapatite – chief crystal in bone formation
  ■ Fluorapatite – fluoride displaces the hydroxy portion; resistant to bone dissolution (to maintain bone integrity)

What are calcium’s functions in body fluids?

• Regulates transport of ions across cell membranes (nerve transmission)

• Essential for muscle contraction (eg. heartbeat)

• Allows secretion of hormones, digestive enzymes, neurotransmitters

• Activates cellular enzymes that regulate many processes

• Helps maintain normal blood pressure

• Plays essential role in blood clotting

  
  

How does calcium participate in disease prevention?

• chronic disease prevention

  • bc of DASH diet that increases mag, calcium, potassium

• Maybe diabetes, cholesterol, colon cancer, osteoporosis

How does calcium interact with body weight?

• maybe stimulates hormone involved in the breakdown of stored fat

What organs and hormones regulate calcium?

• Kidneys, Intestines, Bones

• Hormones: Calcitonin, parathyroid hormone

• Vit D

• Elevated blood calcium —> calcium rigor

• Low blood calcium —> calcium tetany

  
  

What enhances and inhibits calcium absorption?

• enhance

  • stomach acid

  • vit D

  • Lactose

• inhibit

  • Lack of stomach acid or vit D

  • High potassium intake

  • Phytates (seeds, nuts, grains)

  • Oxalates (spinach, sweet potato, beets)

What happens with inadequate calcium intake?

• Inadequate intake prevents development of peak bone mass and density

• Osteoporosis

  • Adult bone loss

  • Brittle, fragile bones resul4ng in fractures

  • Major health problem among many older adults

  • Silent – no major signs or symptoms to body indicating bones are losing calcium

  • Measuring blood levels is not helpful

What can happen with excessive intake of calcium?

• kidney stones (dehydration and oxalates too tho)

• interference with mineral absorption

• constipation

What is the RDA and UL of calcium?

• RDA: 1000mg/day (19-50yr)

• UL: 2500mg/d (Adults 19-50yr)

What are some calcium sources?

• Milk/Milk Products

• Vegetables
  – rutabaga, broccoli, Bok choy, kale

• Small fishes with bones / stock form bones

• Almonds

• Calcium-fortified foods

• Plant-based milk, tofu, OJ, etc

Where is phosphorus in the body?

• 85% combined with Calcium in the hydroxyapatite crystals

• 15% in soft tissue (muscle and kidneys)

What are the functions of phosphorous?

• Part of cell’s genetic material (RNA, DNA)

• Cell membrane (phospholipid molecules)

• Assists in energy transfer (carry/store/release energy)

• Buffering system (Acid-base balance of cellular fluid)

Explain deficiency/toxicity of phosphorous

• deficiency

  • Rare- bone pain, muscle weakness

• toxicity

  • Calcium excretion

  • Calcification of kidneys

What is the RDA/UL of phosphorous, what about food sources?

• RDA: 700mg

• UL: 4000mg

• Food sources:

  • animal protein

  • cottage cheese

  • salmon

  • milk

  • steak

  • navy beans

How does the body synthesize vit D?

• can synthesize it with the help of sunlight

• UV light shines on 7-dehydrocholesterol in the skin

• 7-DC transformed to inactive vitamin D3 precursor is absorbed
  directly into the blood

• Liver & kidney convert precursor to active 1, 25-hydroxy vit D3

What factors affect sun exposure?

• Air pollution – clouds, smog, smoke

• City living – tall buildings, window glass, window screen

• Clothing – darker vs. lighter colors

• Homebound / Institutionalized / night shift work

• Dark skin – need longer exposure vs. light skin

• Season – warmer summers

• Sunscreen – SPF 8+ prevent synthesis

• Time of day – mid-day hours best

• Geography – lack of direct sunlight, Sept- March (Canada), Nov-Feb (US)

• Sunbathing – risks of premature wrinkling, skin cancer concerns

What are the functions of vit D?

• Helps absorption of dietary Calcium & Phosphorus (from skeleton, digestive tract, kidneys) to maintain bone integrity

• Acts as a hormone to raise level of blood Calcium when dietary Calcium is lacking

• Affects health of bones & teeth (ensures sufficient Calcium & Phosphorus available in blood)

• Stimulates maturation of cells, esp. cells of the immune system to fight off infections & some cancers (colon, prostate) – further evidence is needed to confirm findings

What are some symptoms of vit D deficiency?

• Calbindin slows (protein that binds calcium) —>unabsorbed Ca passing through GI tract —>less delivery of Ca to bones —> calcium deficiency —> osteoporosis

• rickets (protruding pigeon chest, bow legs, beaded ribs, belly)

• osteomalacia in adults (week/soft spine and leg bones)

What are some vit D excessive intake symptoms?

• (5x DRI causes loss of appetite, depression, high blood calcium levels (calcium deposits in heart, arteries, kidneys, brain, nerves, bones)

What are the food sources and recommendations of vit D?

• Naturally only occurs in a few foods
  – Eggs (yolk), fatty fish (salmon, sardines, mackerel)

• Fortified milk

• RDA: 600IU or 15ug

• UL: 4000ug

Why are older ppl more at risk of vit D deficiency? What do you do?

• Skin, liver and kidneys lose capacity to make and activate vitamin D

• Decreased milk intake

• Limited sunlight

• 400IU (10ug) of vitamin D in supplement PLUS dietary intake

Where is magnesium in the body?

• More than half the body’s Mg is in the bones

• remaining is in muscle and soft tissues, except ~1% that remains in
  extracellular fluid

What are the functions of magnesium?

• Needed for release & use of energy

  • metabolism of calcium, vitamin D and vitamin K

• Assists enzyme actions and in muscular contraction /relaxation

  • Ca promotes contraction/Mg relaxes muscles —> helps to maintain BP

• Assists in nerve transmission

• Holds Calcium in the enamel of teeth

What are some food sources and RDA/UL of magnesium?

• Hard water, legumes, pumpkin seeds, nuts, leafy green, whole grains

• RDA: men 400mg, women 310mg

• UL: 350mg (non-food mag)

What are some causes/symptoms of magnesium deficiency?

• Causes:

  • Inadequate intake (easily washed & peeled away during processing)

  • Vomiting and diarrhea

  • Alcoholism

  • Protein malnutrition

• Symptoms:

  • weakness, uncontrollable muscle spasms (fatal in heart), convulsions, hallucinations

What’s magnesium's role in hypertension?

• Adequate amounts protective against heart disease/hypertension

• Consuming hard water (high in Ca + Mg) – have lower incidence of heart disease

• Deficiency results in arterial walls constrict – increasing BP

What happens with excessive magnesium intake?

• Excess supplement or antacids

• Symptoms – diarrhea, dehydration, acid- base imbalance

• Rare, but can be fatal!

What are flouride’s functions, food sources, and recommendations?

• Functions

  • help form bones & teeth as part of more decay-resistant fluorapatite

  • plaque suppressing metabolism & reducing acid produced

• Food Sources

  • drinking water from the tap

  • Fluoridation – 1 ppm public health measure

  • seafood

• Recommendations

  • AI: men 4mg, women 3mg

  • UL: 10mg

Describe fluoride deficiency/toxicity

• deficiency

  • tooth decay and dental carries

• toxicity

  • Fluorosis – irreversible discoloration of teeth

  • Mottled teeth enamel

What’s vit K’s role in bone health?

• synthesis of protein needed in bone formation together with vitamin D

• Osteocalcin: vitamin K needed to bind this protein to minerals needed for bone formation

• vitamin K can decrease bone turnover and prevent fractures

How do you diagnose osteoporosis?

• dual-energy X-ray absorptiometry (DEXA) scan to measure bone mineral density

Who’s at risk of osteoporosis? How to protect from it?

• smokers

• old ppl and women

• inadequate intake of calcium and magnesium

• alcoholics

• Low BMI

• PREVENT: stop all that, get bone density assessments, estrogen therapy, up the calcium and magnesium intake, workout

How do gender and hormones play into steoporosis?

• sex hormones regulate bone turnover

• menopause reduces estrogen levels (bad)- try soy to reverse

• less testosterone in males is also linked

What are the bone growth goals of various age groups?

• Grow strong bones – ages 2-12 y

  • drink flouride, milk, limit screen

• Achieve peak bone mass – 13-30 y

  • physical activity, avoid alcohol/smoke

• Maximize bone retention – 31-50 y

  • exercise and calcium supplements

• Minimize bone loss – 51+ y

  • bone density test, bone restoration supplements