Nutrients Involved in Bone Health

1. 11 Nutrients Involved in Bone Health

2. Bones • Bones are living organs that contain • Bone tissue • Nerves • Cartilage • Connective tissue • Blood vessels supply nutrients to bone to support its activities

3. 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

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)

7. Bone Development • Bonegrowth: 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

9. 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

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 builders) • Synthesize new bone matrix by laying down collagen-containing component of bone

12. 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

13. 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

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

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

17. 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

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

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)

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

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

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

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 Activation of Vitamin D

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: decreased capacity to synthesize vitamin D from the sun • Obesity: lower circulating vitamin D levels

31. 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

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

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

37. 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

39. 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

40. 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

42. 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

43. 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

44. 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)

45. 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

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

47. 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

49. 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

50. 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