Lecture 9 - Bone Health

BONE HEALTH - 206 bones

Bone purposes

1. Provide structure
2. Protect organs
3. Anchor muscles (via tendons)
4. Store calcium
5. Regulates blood pH
6. Bone marrow → blood cells
7. Cartilage: cushions bones at joints

Formation of skeleton

• Osteoblast - formation
  • “B” before “c”- need to build before you breakdown
• Osteoclast - resorption
  • Resorption: recycling of bone
• Osteocyte: mature bone cell
• <28 y.o: # of Osteoblasts > osteoclasts
• At 28 y.o (finished growing): bone formation = resorption
  • Peak density
• >28 y.o: bone resorption (osteoclast) > bone formation (osteoblast)
  • Greater risk of osteoporosis, osteoporotic fractures, frailty

Chart: Male vs Female BMD acquisition (bone mineral density) vs Age (years)

• Modelling: 0-28 y.o.
• Peak bone mass: 28 y.o.
• Remodelling: >28 y.o - gradual bone loss
  • Menopause: ~50 y.o.
  • Paid bone loss: ~60 y.o.
• Men vs women: men have higher BMD due to larger bones (therefore have denser bones ot support larger overall body)
• Estrogen and testosterone: effect bone density
  • Women: menopause= decrease in estrogen= drop off

2 key components of BMD:

1. Vit D: body makes vit D when exposed to UV rays

• Vit D allows the absorption of calcium
• Food sources:
  • Cheese, margarine, butter, fortified milk,
  • Vegan sources: mushrooms, fortified foods (tofu, cereals, yogurt, juice, milk)

1. Calcium

• Dairy:
  • Milk, cheese
• Non-dairy:
  • White beans, dried figs, bok choy, black-eyed peas, broccoli

DRI for Calcium and Vit D by Sex and Age:

• Vit D: 600 IU for all ages and sex; except >70 y.o.: 800 IU
• Calcium:
  • 9-18: (males and females) 1300 mg/day
  • 19-30: (males and females 1000 mg/day
  • 31-50: (males and females) 1000 mg/ day
  • 51-70: (Males) 1000; (females) 1200 mg/d
  • >70: (males and females) >1200 mg/d

Caffeine

• Increase calcium excretion via urine
• Salty (6):
  • Cold cuts and cured meats
  • Poultry
  • Bread and rolls
  • Soup
  • Sandwiches
  • Pizza

Exercise for bone health

• Bones react to weight bearing exercise and training
• Adapt, like progressive overload to muscles

Principles:

1. PA will only affect bone at the skeletal sites that are stressed (or loaded) by the activity
2. For bone hain t occur, the stimulus must be greater than that which the bone experiences. Static loads applied to muscle (such as standing) do not promote increased bone mass
3. Complete lack of activity (immobility, paralysis, bed rest) causes bone loss
4. PA most days of the week, coupled with weight bearing, strength building, and balance-enchanting activities 2 or more time a week, is effective for promoting bone health for most people
5. Any activity that causes impact (ex. Jumping, skipping) may increase bone mass more than low- to moderate-intensity enducrat-type activities
6. Load-bearing physical activities (ex. Jumping or skipping) need not be engaged in for long periods of time to provide benefits to skeletal health
7. PA should include a variety of loading patterns to promote increased bone mass. Be creative in finding ways to add other weight-bearing activities to your daily life.

Osteoporosis

• 1 in 3 women and 1 in 5 men over 50 will experience osteoporosis fracture
• Risk factors:
  • Genetic susceptibility
  • Inactive lifestyle
  • Age (over 45) insufficient mass
  • Growth
• Prevention and treatment
  • Diet
  • Dairy products
  • Restful sleep
  • Calcium and Vit D
  • Limit coffee
  • Stop smoking
  • Limit alcohol

Bone measurement methods:

• Bone density scan = a low dose x-ray which checks an area of the body such as the hip, hand, or foot for signs for mineral loss and bone thinning
• Healthy → Osteopenia → osteoporosis
  • >2 SD= osteoporosis
• Who needs a bone density scan: rx for everyone at risk for osteoporosis or another condition
  • Long-term use of corticosteroids
  • Hormonal imbalance
  • Excessive consumption of alcohol
  • A fam. hx of osteoporosis
  • Low or high body mass
  • Smoking