Nutrition Week 9.docx

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10 Apr 2012
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March 12th
No Bones About it: Nutrients Involved in Bone Health
Introduction to Bones (3 general concepts about bones)
- Bones are dynamic, living organs!
- Have many important roles in the body
- Important to maintain healthy bones
Functions of Bones
Structure and Support
Metabolic Processes
Structural support for organs and body
Storage reservoir for minerals
Protect vital organs
Production of blood cells in bone
Muscle support for movement
Bone Consists of:
- 65% minerals Hardness
o Hydroxyapatite
Calcium and phosphorus crystals
- 35% organic substances Strength and Flexibility
o Collagen (a fibrous protein)
Nutrients Involved in Bone Health
Major Roles
Minor Roles
Vitamin K
Vitamin D
Vitamin A
Bone Development
Determines bone size
Determines bone SHAPE
Maintains bone
Begins in womb
Longitudinal growth
Continues until early
Continues until early
Bone resorption &
Process of Bone Remodeling
- Bone Resorption
o Breakdown of bone by osteoclasts
Secrete enzymes and acids to erode bone surface
o Minerals released into the bloodstream
- Bone Formation
o Formation of bone by osteoblasts
Build collagen matrix
Peak Bone Mass
- Highest amount attained during the years of normal bone growth
o End of adolescence versus late 20s?
o Site specific
- Influenced by:
o Genetics
o Nutrition
o Physical Activity
o Disease
o Drugs
Measuring Bone Status
- Dual energy x-ray absorptiometry (DEXA)
o Measures bone mineral density (BMD)
o Monitor changes in BMD
o Determine risk of osteoporosis
o BMD value compared
o T-score (helps us determine if someone has osteoporosis or not)
BMD Values in Adults
- + 1.0 Normal bone density
- 0.0 Normal bone density
- -1.0 Low bone mass
- -2.0 Low bone mass
- -2.5 Low bone mass
- -3.0 Presence of osteoporosis
- -4.0 Presence of osteoporosis
o T-score: Compares your BMD to average peak bone density of a 30
year old healthy adult of similar age and gender
o -1.0 to -2.5 (low bone mass) Osteopenia (reversible)
Poor Bone Health
- Osteoporosis:
- Most prevalent bone disease in North America
- Bone is porous and thinner
o Low bone mass and deterioration of bone tissue
Increase in bone fragility
Increase in fracture risk
Risk Factors for Osteoporosis
- Non-modifiable
- Nutrient deficiencies
- Age
- Sedentary lifestyle
- Gender
- Smoking
- Ethnicity
- Low body weight
- Fracture History
- Alcohol abuse
- Family History
- Repeated falls
- Hormone deficiencies
- Medications
Age as a Risk Factor
- Risk increases with older age
o BMD decreases gradually with age
o Bone remodeling imbalance
Resorption occurs more rapidly than formation
o Minerals released from inner bone matrix
o Bones become wider and less dense
Gender as a Risk Factor
- Women at higher risk than men
o Lower peak bone mass
o Longer life expectancy
o Hormonal changes
Low estrogen levels cause increased bone resorption and
decreased bone formation
Without estrogen bone remodeling balance is uneven, bone
density decreases
March 14, 2012
Calcium (Ca)
- Most abundant mineral in our body
o Makes up 2% of our body weight
- 99% of Ca found in bones and teeth
o Part of bone structure (hydroxyaptite crystals), providing strength
and rigidity
o Ca bank, helping maintain blood CA levels
Remaining 1% of Ca is in blood and soft tissues, and is the active form
- Helps transmit nerve impulses
o Stimulates release of neurotransmitters, which transfer nerve
impulses between nerve cells
- Helps in muscle contraction in muscle contraction
o Contraction occurs when Ca flows into muscle cells
- Also maintains healthy blood pressure and acid-base balance; initiates blood
clotting; regulates various hormones and enzymes
Normal blood Ca: 2.20- 2.20-2.58 mmol/L
- < 2.20
o Hypocalcemia: convulsions, twitching, spasms, possible heart failure
o To avoid Ca releases from bone (resorption); retained by kidney;
increases absorption from GI tract
- > 2.58
o Hypercalcemia: loss of appetite, nausea, fatigue, muscle weakness,
restlessness, confusion, Ca deposits in soft tissue
o To avoid Ca deposits into bone; excreted by kidney; decreases
absorption from GI tract
How much Ca should we consume?
- RDA for 19 to 50 year old adults is 1000 mg/d
- How much Ca are Canadians actually consuming?
o Women consume 793 mg/d