1. Chapter 11: Nutrients Involved in Bone Health
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2. 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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3. 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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5. 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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7. 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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9. 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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10. 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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11. 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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13. 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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15. 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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16. Calcium Calcium absorption Is enhanced in an acid environment
Requires 1,25-dihydroxyvitamin D
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17. Functions of Calcium 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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19. 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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21. 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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24. 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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25. 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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26. Vitamin D Fat-soluble vitamin
Excess is stored in liver, adipose tissue
Can be synthesized by the body from exposure to UV rays from the sun
Considered a hormone: synthesized in one location and regulates activities in other parts of the body
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28. Functions of Vitamin D
Regulates blood calcium levels (regulates calcium and phosphorus absorption from the small intestine)
Stimulates osteoclasts when calcium is needed elsewhere in the body
Required for bone calcification
May decrease cancer growth
Involved in cell differentiation
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29. Vitamin D Adequacy AI: Assume sun exposure is inadequate
Inadequate sun in the winter (latitude of more than 40°N or more than 40°S)
Darker skin (more melanin pigment) reduces the penetration of sunlight
People >65 years have decreased capacity to synthesize vitamin D from the sun
Obesity causes lower circulating vitamin D levels
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31. Vitamin D Intake Recommendations
RDA: 600 IU for men/women ages 19 to 70; 800 IU for adults over age 70
UL: 4,000 IU for everyone over 9 years of age
Controversy: Recent evidence suggests that the current RDA is not sufficient to maintain optimal bone health and reduce the risks for diseases such as cancer
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33. Sources of Vitamin D Ergocalciferol (D2): plants, supplements
Cholecalciferol (D3): animal foods, sun
Most foods naturally contain little vitamin D
Mostly obtained from fortified foods (e.g., milk)
High amounts: cod liver oil, fatty fish (salmon, mackerel, and sardines)
Vegetarians not consuming milk products receive vitamin D from the sun, fortified soy or cereal products, or supplements
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35. Vitamin D What happens if you consume too much?
Results in hypercalcemia
What if you don't consume enough?
Loss of bone mass: from fat malabsorption
Rickets (children), osteomalacia (adults)
Medications alter vitamin D metabolism and activity: glucocorticoids, phenobarbital
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37. Vitamin K Fat-soluble vitamin stored in the liver
Phylloquinone: plant form (dietary) of vitamin K
Menaquinone: animal form of vitamin K produced by bacteria in the large intestine
Vitamin K functions as coenzyme:
Blood coagulation
Bone metabolism
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39. Vitamin K (cont.) "Gla" protein (bone protein) production
Osteocalcin: secreted by osteoblasts (bone remodeling)
Matrix Gla protein: in protein matrix of bone, cartilage, blood vessel walls, soft tissues. May prevent calcification of arteries, reducing risk of CVD
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40. Vitamin K (cont.) Recommended intake
AI values are 120 μg/day for men and 90 µg/day for women
Sources of vitamin K
Synthesized by bacteria in the large intestine
Green leafy vegetables (kale, spinach, collard greens, lettuce)
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42. Vitamin K (cont.) What if you consume too much?
No known side effects from large quantities
What if you don't consume enough?
Reduced blood clotting, excessive bleeding
Fat malabsorption (celiac disease, Crohn's disease, and cystic fibrosis)
Long-term use of antibiotics can lead to deficiency
Injection of vitamin K at birth for newborns
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43. Phosphorus
Phosphorus is the major intracellular negatively charged electrolyte
An essential component of all cells, found in both plants and animals
Functions of phosphorus
Critical in bone formation
Required for proper fluid balance
Component of ATP, DNA, membranes
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44. Sources of Phosphorus
High in protein-containing foods such as milk, meats, eggs, legumes
In processed foods as a food additive: smoothness, binding, and moisture retention
In soft drinks as phosphoric acid
High phosphorus diet linked with premature mortality in healthy adults
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45. Phosphorus (cont.) What if you consume too much?
Excessive vitamin D supplements or phosphorus-containing antacids can cause high phosphorus levels (muscle spasms and convulsions)
What if you don't consume enough?
Deficiencies are rare in healthy adults
Can occur in alcohol abuse, premature infants, and elderly people with poor diets
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46. Magnesium Kidneys regulate blood magnesium levels
Functions of magnesium
Mineral found in bone structure
Cofactor for over 300 enzyme systems
Required for ATP, DNA, and proteins
Supports vitamin D metabolism, muscle contraction, and blood clotting
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47. Magnesium (cont.) Recommended intake
RDA varies based on age and gender
UL (pharmacological): 350 mg/day
Sources of magnesium
Green leafy vegetables, whole grains, seeds, nuts, seafood, beans, some dairy products
Dietary protein enhances absorption and retention
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49. Magnesium (cont.) What if you consume too much?
Excess supplements cause diarrhea, nausea, cramps, dehydration, acid–base imbalances
Hypermagnesemia occurs in individuals with impaired kidney function (antacid)
What if you don't consume enough?
Hypomagnesemia: results in hypocalcemia; associated with osteoporosis, heart disease, high blood pressure, type 2 diabetes
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50. Fluoride Trace mineral, stored in teeth and bones
Combines with calcium and phosphorus to form fluorohydroxyapatite to form teeth
Functions of fluoride
Develop and maintain teeth and bones
Combines with calcium and phosphorus to protect teeth from bacteria
Stimulates bone growth
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51. Fluoride (cont.) Recommended intake
AI varies by gender and increases with age, ranging from 1 to 4 mg/day
Sources of fluoride
Fluoridated dental products
Fluoridated water (not in bottled water)
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52. Fluoride (cont.) What if you consume too much fluoride?
Fluorosis (excess fluoride) increases the protein content of tooth enamel and makes teeth porous; teeth become stained and pitted
What if you don't consume enough?
Dental caries (cavities)
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54. Osteoporosis Most prevalent disorder affecting bone health
Characterized by:
Low bone mass
Deterioration of bone tissue
Fragile bones leading to bone-fracture risk
Bone compaction: decreased height
Shortening and hunching of the spine: kyphosis (dowager's hump)
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55. Osteoporitic vertebrae (left) and healthy vertebrae (right).
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57. Osteoporosis (cont.) Risk factors include: Age Gender
Tobacco, alcohol, and caffeine
Poor nutrition
Physical inactivity
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59. Osteoporosis Risk: Age
Bone mass decreases with age
Age-related hormonal (estrogen and testosterone) changes influence bone density
Decreased vitamin D metabolism with age
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60. Osteoporosis Risk: Gender And Genetics
80% of Americans with osteoporosis are women
Women have lower bone density than men
Low estrogen production increases bone loss: postmenopausal women and adolescent girls (extreme dieting)
Caucasian women of low body weight with first-degree relative (mother or sister) with osteoporosis at greater risk
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61. Osteoporosis Risks: Smoking/Poor Nutrition
Cigarette smoking effects hormones that influence bone formation and resorption
Alcoholism is associated with fractures
Caffeine increases urinary calcium loss
Dietary protein and calcium interaction
Low calcium and vitamin D intakes result in low bone density
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62. Osteoporosis Risk: Physical Inactivity
Regular exercise postively stresses bone tissues, stimulates bone density
Weight-bearing activities (walking, jogging) can help increase bone mass
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63. Nutrition and Osteoporosis
Fruit and vegetable consumption associated with improved bone health
Good sources of vitamins C and K, as well as magnesium
Protein: effect on bone health is controversial
High intake may increase calcium loss
Low protein intake also associated with bone risks
Calcium & vitamin D are important throughout the life span
Sodium: high intakes appear to have a negative impact, but studies are inconclusive
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64. Treatment for Osteoporosis
There is no cure for osteoporosis
Factors that slow the progression of osteoporosis:
Adequate calcium and vitamin D intake
Regular (weight-bearing) exercise
Resistance training
Certain medications (may have side effects)
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