The science of nutrition 4th edition thompson manore vaughan chapter 11

Chapter 11 Lecture

Chapter 11:
Nutrients
Involved in Bone
Health

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Bones
• Bones are living organs that contain
• Bone tissue
• Cartilage
• Connective tissue
• Nerves and blood run within channels in bone to
support its activities

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Bones (cont.)
• Bone provides strength and flexibility
• Contains about 65% minerals, providing the
hardness of bone
• Contains 35% organic structures for strength,
durability, and flexibility (collagen)
• Hydroxyapatite: mineral crystals around
collagen designed to bear weight

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© 2017 Pearson Education, Inc.


Bone Tissues
• Cortical bone (compact bone)
• 80% of the skeleton
• Outer surface of bone
• Trabecular bone (spongy bone)
• 20% of the skeleton
• Inside of bones (scaffolding)
• Supports outer cortical bone
• Faster turnover rate (sensitive to hormonal
changes and nutritional deficiencies)

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© 2017 Pearson Education, Inc.


Bone Development
• Bone growth: increase in bone size
• Complete by age 18 in girls; age 21 in boys
• Bone modeling: shaping of bone
• Complete by early adulthood
• Exercise and overweight increase thickness
• Bone remodeling: recycling of bone tissue

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© 2017 Pearson Education, Inc.


Bone Development (cont.)
• Bone density: compactness of bones
• Peak bone density: when bones are strongest
• Factors associated with a lower peak bone
density:
• Late pubertal age in boys
• Late onset of menstruation in girls
• Inadequate calcium intake
• Low body weight
• Physical inactivity during the pubertal years

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Bone Remodeling
• Resorption: surface of bones is broken down by
osteoclasts (cells that erode the surface of
bones)
• New bone matrix formed by osteoblasts (bone
builder cells)
• Synthesize new bone matrix by laying down
collagen-containing component of bone

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Bone Remodeling (cont.)
• Bone resorption and formation are equal in
young, healthy adults
• Resorption exceeds new bone formation after
age 40: density begins to decrease
• High peak bone mass through proper nutrition
and exercise: stronger skeleton
• Protective against osteoporosis

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© 2017 Pearson Education, Inc.


Assessing Bone Health
• Dual energy x-ray absorptiometry (DXA or
DEXA)
• Non-invasive measurement of bone density
• Results are compared with average peak
bone density of 30-year-old healthy adult
• T-score is used to assess a person's risk for
fracture and diagnose osteoporosis
• Recommended for postmenopausal women

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© 2017 Pearson Education, Inc.


Nutrients for Bone Health
• Calcium is the most recognized nutrient
associated with bone health
• Also essential for bone health:
• Vitamins D and K
• Phosphorus
• Magnesium
• Fluoride

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Calcium
• Calcium absorption
• Is enhanced in an acid environment
• Requires 1,25-dihydroxyvitamin D

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Functions of Calcium
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Provides structure for bones and teeth
Assists with acid−base balance
Assists in transmission of nerve impulses
Assists in muscle contraction
Maintains healthy blood pressure
Initiates blood clotting
Regulates hormones and enzymes

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© 2017 Pearson Education, Inc.


Calcium Intake
• Adequate Intake (AI) varies with age and
gender: 1,000 mg to 1,300 mg/day
• Upper limit (UL): 2,500 mg
• Bioavailability: Body's ability to absorb and
utilize calcium depends on
• Individual's age and calcium need
• Dietary calcium and vitamin D
• Binding factors (phytates, oxalates) in foods

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© 2017 Pearson Education, Inc.

Sources of Calcium
• Excellent sources include milk products
• Skim milk, low-fat cheese, nonfat yogurt
• Other good sources include
• Green leafy vegetables (kale, collard greens,
broccoli, and cabbage are low in oxalates)
• Fortified foods (orange juice, soy milk)
• Fish with edible bones (sardines, salmon)

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© 2017 Pearson Education, Inc.


© 2017 Pearson Education, Inc.


Excess Dietary Calcium
• Excess dietary calcium is excreted in feces
• Mineral imbalances from supplements
• Hypercalcemia (high blood calcium)
• Cause: cancer or parathyroid hormone (PTH)
overproduction
• Symptoms: fatigue, appetite loss,
constipation, mental confusion, calcium
deposits in soft tissues

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Calcium Deficiency
• Osteoporosis from long-term calcium deficiency
• Hypocalcemia (low blood calcium)
• Causes: kidney disease, vitamin D deficiency,
or diseases that inhibit the production of PTH
• Symptoms: muscle spasms and convulsions

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