© 2011 Pearson Education, Inc. 11 Nutrients Involved in Bone Health

© 2011 Pearson Education, Inc. Bones Bones are living organs that contain Bone tissue Nerves Cartilage Connective tissue Blood vessels supply nutrients to bone to support its activities

© 2011 Pearson Education, Inc. Bones Bone provides strength and flexibility Contains about 65% minerals, providing the hardness of bone Contains 35% organic structures for strength, durability, and flexibility Collagen: fibrous protein in bone tissue Hydroxyapatite: mineral crystals around collagen designed to bear weight

© 2011 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)

© 2011 Pearson Education, Inc.

Bone Development Bone growth: increase in bone size Complete by age 14 in girls; age 17 in boys Bone modeling: shaping of bone Complete by early adulthood Exercise and overweight increase thickness Bone remodeling: recycling of bone tissue

© 2011 Pearson Education, Inc.

Bone Development 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

© 2011 Pearson Education, Inc. 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 builders) Synthesize new bone matrix by laying down collagen-containing component of bone

© 2011 Pearson Education, Inc.

Bone Remodeling 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

© 2011 Pearson Education, Inc. Bone Health Dual energy x-ray absorptiometry (DXA) Measures 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

© 2011 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

© 2011 Pearson Education, Inc. Calcium Calcium absorption Is enhanced in an acid environment Requires 1,25-dihydroxyvitamin D Calcium Metabolism

© 2011 Pearson Education, Inc. Functions of Calcium Provides structure for bones and teeth Assists with acid−base balance Transmission of nerve impulses Assists in muscle contraction Maintains healthy blood pressure Initiates blood clotting Regulates hormones and enzymes

© 2011 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

© 2011 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)

© 2011 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

© 2011 Pearson Education, Inc. 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

© 2011 Pearson Education, Inc. 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

© 2011 Pearson Education, Inc.

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 Activation of Vitamin D

© 2011 Pearson Education, Inc. 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: decreased capacity to synthesize vitamin D from the sun Obesity: lower circulating vitamin D levels

© 2011 Pearson Education, Inc.

Vitamin D Adequacy AI: 5 to 15 µg/day depending on age UL: 50 µg/day for all age groups Controversy: recent evidence suggests that the current AI is not sufficient to maintain optimal bone health and reduce the risks for diseases such as cancer

© 2011 Pearson Education, Inc.

Sources of Vitamin D Ergocalciferol (D 2 )—plants, supplements Cholecalciferol (D 3 )—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

© 2011 Pearson Education, Inc.

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

© 2011 Pearson Education, Inc.

Vitamin K Fat-soluble vitamin stored in the liver Phylloquinone—plant form of vitamin K Menaquinone—animal form of vitamin K produced by bacteria in the large intestine Functions of vitamin K Blood coagulation Bone metabolism

© 2011 Pearson Education, Inc.

Vitamin K “Gla” protein production Osteocalcin: secreted by osteoblasts (bone remodeling) Matrix Gla protein: in protein matrix of bone, cartilage, blood vessel walls, soft tissues

© 2011 Pearson Education, Inc. Vitamin K 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, vegetable oils

© 2011 Pearson Education, Inc.

Vitamin K 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

© 2011 Pearson Education, Inc. Phosphorus Phosphorus (as phosphate) is the major intracellular negatively charged electrolyte Functions of phosphorus Critical in bone formation Required for proper fluid balance Component of ATP, DNA, membranes

© 2011 Pearson Education, Inc. Sources of Phosphorus High in protein-containing foods such as milk, meats, eggs In processed foods as a food additive: smoothness, binding, and moisture retention In soft drinks as phosphoric acid (milk- displacement effect)

© 2011 Pearson Education, Inc. Phosphorus 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

© 2011 Pearson Education, Inc. 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

© 2011 Pearson Education, Inc. Magnesium 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

© 2011 Pearson Education, Inc.

Magnesium 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

© 2011 Pearson Education, Inc. Fluoride Trace mineral Stored in teeth and bones Functions of fluoride Develop and maintain teeth and bones Combines with calcium and phosphorus to protect teeth from bacteria

© 2011 Pearson Education, Inc. Fluoride 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)

© 2011 Pearson Education, Inc. Fluoride 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)

© 2011 Pearson Education, Inc.

Osteoporosis A disease characterized by Low bone mass Deterioration of bone tissue Fragile bones leading to bone-fracture risk Compaction of bone: decreased height Shortening and hunching of the spine: kyphosis (dowager’s hump)

© 2011 Pearson Education, Inc.

Osteoporosis Risk factors for osteoporosis include: Age Gender Smoking Poor nutrition Physical inactivity

© 2011 Pearson Education, Inc.

Age Bone mass decreases with age Age-related hormonal (estrogen and testosterone) changes influence bone density Decreased vitamin D metabolism with age

© 2011 Pearson Education, Inc. Gender 80% of Americans with osteoporosis: women Women have lower bone density than men Low estrogen production increases bone loss: postmenopausal women and adolescent girls (extreme dieting) At risk: Caucasian women of low body weight with first-degree relative (mother or sister) with osteoporosis

© 2011 Pearson Education, Inc. Smoking and 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

© 2011 Pearson Education, Inc. Physical Inactivity Regular exercise stresses bone tissues, stimulates bone density Weight-bearing activities (walking, jogging) are helpful in increasing bone mass

© 2011 Pearson Education, Inc. Female Athlete Triad Low energy availability (with or without eating disorders) Amenorrhea: hormonal changes (estrogen reduction) result in loss of menstruation Osteoporosis

© 2011 Pearson Education, Inc. Treatment for Osteoporosis There is no cure for osteoporosis These slow the progression of osteoporosis: Adequate calcium and vitamin D intake Regular exercise (weight-bearing) Anti-resorptive medications