Chapter 11: Nutrients Involved in Bone HealthThe Composition of Bone Provides Strength and Flexibility- Bones need to be both strong and flexibleo 65% of bone tissue is made of minerals that provides hardnesso 35% is a mixture of organic substances that provide strength, durability, and flexibility- Collagen: fibrous protein- Hydroxyapatite: tiny crystals that cluster around the collagen fiberso Enables bones to bear weight while responding to demands form movement- Cortical bone: compact bone, is very denseo 80% of the skeleton o The outer surface of bones- Trabecular boneo 20% of the skeletono Inside and the ends of long boneso Spongy boneo Have a faster turnover rate than cortical boneBone Growth and Modeling Determine the Size and Shape of our Bones- Bone growth: the size of bone increaseso Most girls reach their adult height by 14, and boys 17- Bone modeling: the process by which the shape of bones is determinedo Can still increase in thickness if they are stressed by repetitive exercise such as weight training or by being overweight or obeseBone Remodeling Maintains a Balance Between Breakdown and Repair- Bone density: compactness of bones- Peak bone density: the point at which bones are strongesto Lower peak density include: later pubertal age in boys and late onset of menstruation in girls; inadequate calcium intake; low body weight; and physical inactivity during the pubertal yearso Before 30 we have peaked bone mass- Remodeling: bone recycling- Resorption: bone is broken down- Osteoclasts: erode the bone surface- Osteoblasts: bone builders, new bone is formed o Synthesize new bone matrix by laying down the collagen-containing organic component of boneo In young healthy adults, the processes of bone resorption and formation are equalo Around 40, bone resorption begins to occur more rapidly than bone formation Results in an overall loss in bone densityo High peak bone mass through proper nutrition and exercise Stronger skeletonHow Do We Assess Bone Health?- Dual energy x-ray absorptiometry: DEXA, measures bone densityo Compared to the average peak bone density of a 30 year old healthy adulto T-score: asses the risk of fracture and determine whether or not the person has osteoporosiso Recommended for post-menopausal womenA Profile of Nutrients That Maintain Bone HealthCalcium- Functionso Provide structure to the bones and teetho Stored in the hydroxyapatite crystalso Alkaline, basic Assisting with acid-base balanceo Can’t survive for long if our blood calcium level rises above or falls below a very narrow rangeo Critical for the normal transmission of nerve impulseso Assists in muscle contraction Stimulated by calcium flowing into the muscle cell; muscles relax when calcium is pumped back outsideo Secretion of parathyroid hormone (low blood calcium levels)o Secretion of calcitonin( high blood calcium levels)o Maintenance of healthy blood pressure, the initiation of blood clotting, and the regulation of various hormones and enzymes- RDIo 19-50 years 1,000 mg o Over 50 1,200 mgo UL: 2,500 mgo Bioavailability: the degree to which the body can absorb and utilize any given nutrient Depends in part on a person’s age and his or her need for calcium o Dietary factors can also affect the absorption of calcium Binding factors such as phytates and oxalates Vitamin d- Food sourceso Skim milk, low-fat cheeses, and non-fat yogurto Green leafy vegetableso Calcium-fortified juices, soymilk, rice milk, and tofu processed with calciumo Canned fish with bones- Toxicityo Usually excreted in feceso Toxicity from supplements can lead to health problems Hypercalcemia: blood calcium levels reach abnormally high concentrations- Can be caused by cancer and by overproduction of pth- Symptoms: fatigue, loss of appetite, constipation, and mental confusion,coma, and death- Calcium deposits in the soft tissue- Deficiencyo No short-term symptomso Long-term Hypocalcemia: abnormally low level of calcium in the blood- Cause: kidney disease, vitamin d deficiency, and diseases that inhibit theproduction of pth- Symptoms: muscles spasms and convulsionsVitamin D- Fat soluble, excess amounts are stored in the liver and adipose tissue- The body can synthesize using energy from exposure to sunlight- Considered a hormone because it is made in one part of the body, yet regulates various activities in other parts of the body- Functionso Regulate blood calcium levels Regulates the absorption of calcium and phosphorus from the small intestineo Works with pth to stimulate osteoclasts to break down bone when calcium is needed elsewhere in the bodyo Calcification of the bone- RDIo Synthesized during the time of day when the sun’s rays are strongesto Darker skin reduces the penetration of sunlighto 65< decrease in their capacity to synthesize vitamin d from the suno Obesity is associated with lower levels of circulation vitamin do 19-50 5mgo 50-70 10 mgo 70< 15 mgo UL 50 mgo Current research says that the current AI is not sufficient- Food sourceso Two forms of vitamin d Ergocalciferol- Vitamin d 2- Plant foods- May also be used in vitamin d supplements Cholecaciferol- Vitamin D 3- Animal foods and synthesize from the suno Fortified milko Cod liver oil, fatty fish, and certain fortified cereals- Toxicityo Hypercalcemia- Deficiencyo Loss of bone masso Malabsportion of fato In children, ricketso In adults, osteomalaciaVitamin K- Fat-soluble stored primarily in the liver- Phylloquinone: primary dietary form of vitamin ko Found in plants- Menaquinone: produced by bacteria in the large intestineo Animal form- Functionso Coagulation of bloodo Two bone proteins, “Gla” proteins Osteocalcin- Secreted by osteoblasts Matrix gla protein- Located in the protein matrix of bone and is also found in cartilage, blood vessel walls, and other soft tissues- RDIo 120-90 mgo No UL- Food sourceso Green leafy vegetables- Toxicityo None- Deficiencyo Reduced ability to form blood clots, leading to excessive bleedingo Rare in humans More likely for malabsorption of fat IE celiac disease, crohn’s disease, and cystic firbrosis Long term use of antibiotics Newborns are usually given a shot of vitamin k at birthPhosphorus- Major intracellular negatively charged electrolyte- Functionso Critical role in bone formationo 85% stored in bones- Food sourceso Milk, meats, and eggso Found in many processed foods as a food additive Smoothness, binding, and moisture retention Acid is added to
View Full Document
Unlocking...