Jaymie TicknorIntro Nutrition Science 2460 Sect. 00223 June 2014Chapter #9 : Nutrients Involved in Bone Health How Do Our Bodies Maintain Bone Health?The Composition of Bone Provides Strength and Flexibility● Collagen: a protein that forms strong fibers in bone and connective tissue○ Provides strength, durability, and flexibility● Hydroxyapatite: calcium and phosphorus form these tiny crystals that cluster around the collagen fibers● Cortical Bone (Compact Bone): a dense bone tissue that makes up the outer surface of all bones as well as the entirety of most small bones of the body● Trabecular Bone (Spongy Bone): a porous bone tissue that makes up only 20% of our skeleton and is found within the ends of the long bones, inside the flat bones (sternum, ribs, and most bones of the skull), and inside the bones of the pelvis○ Bone fractures caused by aging are usually found in this type of boneThe Constant Activity of Bone Tissue Promotes Bone HealthBone Growth and Modeling Determine the Size and Shape of Our Bones● Bone Modeling: process by which the shape of our bones is determined● Bone Density: the degree of compactness of bone tissue, reflecting the strength of the bones○ Peak bone density is the point at which a bone is strongestBone Remodeling Maintains a Balance Between Breakdown and Repair● Remodeling: the two-step process by which bone tissue is recycled○ Includes the breakdown of existing bone and the formation of new bone● Resorption: the process by which the surface of bone is broken down by cells called osteoclasts○ Outpaces bone formation at age 40● Osteoclasts: cells that erode the surface of bones by secreting enzymes and acids that diggrooves into the bone matrix● Osteoblasts: cells that prompt the formation of new bone matrix by laying down the collagen-containing component of bone, which is then mineralized● Osteoporosis: a disorder characterized by low-density bones that fracture easilyHow Do We Assess Bone Health● Dual Energy X-ray Absorptiometry (DXA or DEXA): currently, the most accurate tool for measuring bone density● T-score: a comparison of an individual’s bone density to the average peak bone density of a 30-year-old healthy adultA Profile of Nutrients That Maintain Bone HealthCalcium● Calcium is the most abundant mineral in the bodyFunctions of Calcium● Parathyroid Hormone (PTH): a hormone secreted by the parathyroid gland when bloodcalcium levels fall○ Also known as parathormone, it increases blood calcium levels by stimulating the activation of vitamin D, increasing reabsorption of calcium from the kidneys, and stimulating osteoclasts to break down, which releases more calcium into the bloodstream● Calcitonin: a hormone secreted by the thyroid gland when blood calcium levels are too high○ Inhibits the actions of vitamin D, preventing reabsorption of calcium in the kidneys, limiting calcium absorption in the small intestine, and inhibiting the osteoclasts from breaking down bone○ Inhibits absorption of calcium by the kidneys and intestine● Calcium Tetany: a condition in which muscles experience twitching and spasms as a result of inadequate blood calcium levels● Calcium Rigor: a failure of muscles to relax, which leads to a hardening or stiffening of the muscles○ Caused by high levels of blood calciumHow Much Calcium Should We Consume?● Bioavailability: the degree to which our body can absorb and utilize any given nutrient● Our bodies cannot absorb more than 500 mg of calcium at any one time● Oxalate found in plant foods binds dietary calcium making it less available for absorptioninto the bodyWhat Happens If We Consume Too Much Calcium● Hypercalcemia: a condition marked by an abnormally high concentration of calcium in the bloodWhat Happens If We Don’t Consume Enough Calcium?● Hypocalcemia: a condition characterized by an abnormally low concentration of calciumin the blood● Blood calcium levels fall, PTH stimulates osteoblasts to breakdown bones and release calciumVitamin D● Vitamin D is considered a hormone because it is made in one part of the body yet regulates various activities in other parts of the body○ Regulates calcium absorption and utilization● Cholecalciferol: vitamin D3, a form of vitamin D found in animal foods and the form we synthesize from the sun● Calcitriol: the primary active form of vitamin D in the body● The vitamin D sufficiency line is the northernmost point at which adequate vitamin D synthesis is possibleVitamin D: Fish, Fortified Foods, Supplements, or Sunlight● Ergocalciferol: vitamin D2, a form of vitamin D found exclusively in plant foodsWhat Happens If We Don’t Consume Enough Vitamin D?● Rickets: a vitamin D-deficiency disease in children○ Signs include deformities of the skeleton, such as bowed legs and knocked knees○ Severe rickets can be fatal● Osteomalacia: a vitamin D-deficiency disease in adults, in which bones become weak and prone to fracturesVitamin K● Phylloquinone: the primary dietary form of vitamin K and also formed found in plants● Menaquinone: animal form of vitamin K produced by bacteria in the large intestine● Prothrombin: a protein that plays a critical role in blood clotting● Osteocalcin: a protein associated with bone turnover● This is a coenzyme in the regulation of blood coagulationPhosphorusHow Much Phosphorus Should We Consume?● Milk-Displacement Effect: soft drinks take the place of milk or calcium-fortified milk alternatives in our diets, depriving us of calcium and vitamin DMagnesiumFunctions of Magnesium● Magnesium is a critical cofactor (needed for an enzyme to be active) for more than 300 enzymes systems and is necessary for the production of ATP○ Deficiencies disrupt mineral retention by kidneysWhat Happens If We Consume Too Much Magnesium?● Hypermagnesemia: a condition marked by an abnormally high concentration of magnesium in the bloodWhat Happens If We Don’t Consume Enough Magnesium?● Hypomagnesemia: a condition characterized by an abnormally low concentration of magnesium in the bloodFluorideFunctions of Fluoride● Fluorohydroxyapatite: fluoride combines with calcium and phosphorus to form this○ More resistant to destruction by acids and bacteria than is hydroxyapatiteWhat Happens If We Consume Too Much Fluoride?● Fluorosis: a condition, marked by staining and pitting of the teeth, caused by an abnormally high intake of