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Bone Health (About bones (Bone formation & maintenance (Development…

- - - - Provide structural support
        
        Organs are protected by bones
        
        Strong and flexible
        
        Muscles are attached to bones by tendons
        
        Jawbone and teeth allow for chewing of food
      - Provide functional support
        
        Bones contain mineral crystals in protein matrix (osteoid)
        
        Bones contain nerves, cartilage, and connective tissue
        
        RBC, WBC, platelets are manufactured in bone marrow
      - have ~65% mineral matter that provides strength & rigidity
      - have ~35% organic matter that provides flexibility
      - are very metabolically active tissue
      - act as a Calcium bank for depositing & removal of calcium
  - - - Ivory-like, dense, and strong
        
        Slow to turnover
        
        ~80% of our skeleton
      - Can be found
        
        on the outer surface of all bones
        
        In smaller bones
    - - Lace-like, less dense, dynamic
        
        Sensitive to hormones that regulate blood Ca levels
        
        20% of our skeleton
      - Healthy constituents are...
        
        Protein matrix (osteoid) providing flexibility
        
        Mineral crystals in the matrix providing strength
      - Can be found...
        
        at the end of longer bones
        
        in the spinal vertebrae
        
        Inside of flat bones (e.g. ribs)
        
        Pelvis bones
  - - - Osteoclasts
        
        ...that break down bone
      - Osteoblasts
        
        ...that build bone
    - - Remodeling (density, resorption and formation)
      - Modelling (shape)
      - Growth (size and length)
    - - 100% of bone is rebuilt during the first year of life
      - Osteoblasts outbuild osteoclasts' breakdown
    - - Bone is only built under the physical stress of exercise
      - Osteoblasts lose activity, while osteoclasts remain active
      - Osteoclast cell resorption require vitamin A
  - - - Falling blood Ca
        
        Signals parathyroid glands to secrete parathyroid hormone, which...
        
        stimulates the activation of vitamin D
        
        stimulates Ca absorption in the kidneys
        
        stimulates osteoclasts to break down bone and release Ca
        
        Inhibits calcitonin secretion
      - Rising blood Ca
        
        Signals the thyroid gland to secrete calcitonin, which...
        
        Inhibits vitamin D (calcitriol) activation
        
        Prevents Ca resorption in the kidneys
        
        Limits Ca absorption in the intestine
        
        Inhibits osteoclasts from breaking down bone and releasing Ca
      - In healthy individuals, blood Ca levels do not represent Ca density in bone
    - - mostly through absorption in the body
      - slightly through renal excretion
      - tightly by parathyroid hormone, vitamin D, calcitonin
  - - - Non-invasive
        
        Very low x-ray energy scan
        
        Painless & quick
        
        Scans entire body or specific areas
        
        Generates T-score by comparing results to healthy 30 year-old data of same gender & race
      - T-score
        
        lower than -2.5 (osteoporosis)
        
        Increased risk of fracture
        
        -1 to -2.5 (osteopenia)
        
        Low bone mass, increased risk of fracture
        
        +1 to -1 (normal)
    - - Sound waves are used to measure density
        
        Often uses the heel
        
        Non-invasive, painless
    - - X-ray measure heel, wrist, and finger only
        
        Non-invasive, painless
- - - - Plant foods
        
        Leafy greens
        
        Broccoli
        
        Brussel sprouts
        
        Asparagus
        
        Cauliflower
        
        Avocado
      - Animal foods
        
        Liver
        
        Eggs
        
        Cow milk
      - Bacterial synthesis in the colon
      - Resistant to losses during cooking
    - - Calcium mineralization of bone
        
        Needed for osteoblasts to produce osteocalcin
        
        Osteocalcin is a calcium-binding hormone that promotes Ca mineralization
      - Blood clotting
        
        Vitamin K is critical because
        
        infants are born with a sterile gut without bacterial synthesis
        
        it takes weeks to establish bacterial synthesis
        
        Infants receive doses of vitamin K shortly after birth to prevent hemorrhaging
        
        Fibrin
        
        ...is made of 13 proteins
        
        Vitamin K is required for the synthesis of 4 of those proteins
    - - is rare
      - can hinder effects of anticoagulant medications
      - Symptoms include
        
        RBC hemolysis
        
        Jaundice
        
        Brain damage
    - - is seen in infants due to
        
        low levels in breast milk
        
        no vitamin K synthesis due to a sterile gut
        
        low levels of bacteria even after a few weeks
      - is seen in adults
        
        rarely
        
        with fat malabsorption conditions
        
        with excessive intake of vitamin E, which impairs vitamin K in blood clotting
        
        antibiotics use
    - - Vitamin K Quinone
        
        Plant: phylloquinone, Animal: menaquinone
        
        Absorption
        
        40-80% bioavailability
        
        Storage
        
        mostly in liver, some in adipose tissue
        
        coenzyme for protein synthesis
        
        Endogenous: bacterial synthesis
        
        Exogenous: diet
  - - - Fatty fish (and oils)
        
        Liver
        
        Milk & Fortified alternatives
        
        Egg yolk
        
        Canned fish with bones
    - - Assists in maturity of immune cells
      - Blood Ca regulation & bone mineralization through calcitriol
        
        Raises blood Ca levels by...
        
        Stimulating Ca absorption in the kidneys
        
        Enhancing Ca absorption in the intestines
        
        Stimulating osteoclasts to break down bone releasing Ca
      - Possibly (?) mitigate risk for MS, T1D, T2D & required for normal nerve function
    - - Absorption
        
        ~50% bioavailability
        
        Vitamin D is incorporated in chylomicrons which travel through lymph to the blood
        
        Vitamin D is delivered to the liver via chylomicron remnants
    - - is not caused by...
        
        skin's solar exposure since the body regulates synthesis of Vitamin D to maintain adequate levels
        
        food intake (safe)
      - caused by...
        
        excessive supplement use
      - causes...
        
        Hypercalcemia, the increase of blood Ca levels and decreases Ca deposits in soft tissues + causes irreversible damage
      - At greatest risk are...
        
        infants, who may be given inappropriate amounts of supplements
    - - is seen in children (rickets)
        
        causes improper mineralization, and shaping of bones
        
        increasingly in Canada (use of sunscreen blocks endogenous synthesis)
        
        due to...
        
        Low levels in breast milk
        
        Low dietary intake
        
        Little sun exposure
      - is seen in adults (osteomalacia)
        
        causing...
        
        osteoids (protein matrixs) to not mineralize properly + accumulate, making bones soft & flexible
        
        due to...
        
        Kidney, liver, and intestinal diseases (absorption)
        
        Low vitamin D intake
        
        Little exposure to the sun
        
        Closely spaced + repeated pregnancies
        
        which can be treated by...
        
        increasing dietary intake
        
        controlled exposure of skin to sun
- - - - Properties
        
        Second most abundant mineral in body
        
        Absorption # #
        
        60~90% bioavailability
        
        Blood phosphorus levels regulated by kidneys
        
        ~85% of body phosphorus in HYDROXYAPATITE
      - Functions
        
        Bone health
        
        Provides strength & rigidity in bone as part of HYDROXYAPATITE # #
        
        Fluid balance
        
        Major intracellular anionic electrolyte for proper electrical & fluid balance
        
        By being integral component of...
        
        Phospholipids
        
        Lipoproteins
        
        DNA, RNA
        
        ATP
        
        Activating B-vitamin coenzymes
      - Deficiency
        
        ...is unlikely
        
        Neuromuscular, skeletal, hematological, renal malfunctioning
      - Toxicity
        
        At greatest risk are...
        
        TEENS who consume large amounts of pop drinks
        
        Compromises peak bone density
      - Food sources
        
        Animal Foods:
        
        Milk & dairy products
        
        Fatty fish
        
        Canned fish w/ bones
        
        Plant Foods:
        
        Tofu
        
        Legumes
        
        Dairy alternatives
        
        Soft drinks
    - - Functions
        
        Bone & teeth #
        
        Indirectly affects Ca balance
        
        Mg needed for vitamin D action & production of parathyroid hormone #
        
        Mg can replace Ca in the mineral crystal structure of bone
        
        Holds Ca in teeth, reducing dental caries
        
        Blood & tissue
        
        Required by 300+ enzymes for protein, fat, and DNA synthesis
        
        Inhibits blood clotting (antagonist to Ca)
        
        Stabilizes phosphate group in ATP
        
        Required for neurotransmitter activity (regulated by Mg-dependent adenylate cyclase ensyme system)
        
        Inhibits muscle contraction (blocks Ca ion channel)
        
        Hypertension
        
        Protects against high blood pressure by acting as a vasodilator
        
        Lower rates of heart disease in regions where people drink hard water
        
        Supports normal immune functions
      - Deficiency
        
        Develops slowly because of storage in bone
        
        Severe symptoms are rarely seen in healthy people
        
        There is increased loss from...
        
        heavy perspiration over an extended time
        
        Prolonged vomiting, diarrhea, and diuretics use
        
        Renal disease, alcoholism
        
        Symptoms
        
        Irregular heartbeat
        
        Weakness, disorientation, irritability
        
        Hypertension
        
        Tetany at extreme low levels of Mg (same as Ca)
      - Properties
        
        Body contains ~25g Mg, distributed in...
        
        Bones (60%, and is a high reservoir of Mg), muscle (20%), other tissues (20%)
        
        Absorption
        
        ~50% bioavailability
        
        Reduced by high fibre intake
        
        Influenced by high Ca intake (supplements)
        
        Excreted through kidneys
        
        Part of chlorophyll in plants, but is present in many foods
      - Toxicity
        
        No known toxicity
      - Food sources
        
        Animal foods
        
        Milk
        
        Yogurt
        
        Halibut
        
        Plant foods
        
        Leafy greens
        
        Whole grains
        
        Legumes
        
        Beans
        
        Tofu
        
        Nuts and seeds
        
        Mg-containing hard water
    - - Properties
        
        Absorption
        
        ~25-30% bioavailability
        
        Enhanced absorption #
        
        Mostly absorbed in duodenum (slightly acidic, increases solubility)
        
        Enhanced by lactose, which...
        
        Creates absorbable complex for calcium
        
        Enhanced by estrogen, which...
        
        Enhances synthesis of active vitamin D needed for transcellular absorption in intestinal cells
        
        Young age (Ca absorbed more by younger people than elderly)
        
        Enhanced by increased demand for calcium...
        
        during growth periods, pregnancy (~50% absorbed)
        
        Decreased absorption #
        
        Food constituents
        
        High fibre diets (~50+g per day)
        
        Phytic acid (whole grains, legumes) and oxalic acid (vegetables ie. spinach, rhubarb, Swiss chard)
        
        Very high FAT intake (steatorrhea)
        
        Polyphenols (tannins in tea, chlorogenic acid in coffee)
        
        Vitamin D deficiency
        
        Supplement use
        
        Magnesium and phosphorus, iron and zinc (especially w/ low Ca intake)
        
        Choose Ca supplements that are less than or equal to 500 mg/dose, because...
        
        % absorbed inversely proportional to Ca intake
        
        Menopause, due to...
        
        decrease in estrogen -> less synthesis of active vitamin D
        
        Old age, due to...
        
        decrease in stomach acidity -> decreased absorption efficiency
        
        Mineral of the greatest quantity in body (40% of total body mineral content)
        
        Required by all cells in body
        
        Blood Ca levels do not indicate body Ca status/reflect dietary intake because...
        
        Blood Ca is tightly regulated by hormonal action (parathyroid hormone, calcitriol (active vitamin D), calcitonin)
      - Food sources
        
        Animal foods:
        
        milk & dairy products
        
        canned fish w/ bones (ie. salmon, sardines)
        
        soup stock made from fish/meat bones
        
        Plant foods:
        
        fortified plant-based milks
        
        fortified products (ie. energy bars, orange juice)
        
        tofu made w/ Ca salt
        
        some green leafy vegetables
        
        Some green leafy vegetables have high Ca content but low bioavailability (due to oxalic acid & fibres present, ie. spinach)
        
        Some green leafy vegetables have high Ca bioavailability but low Ca content (ie. cauliflower, kale, Brussel sprouts)
      - Toxicity
        
        Caused by hyperparathryoidism
        
        At greatest risk are...
        
        People with kidney disease
        
        ...which is the overproduction & secretion of parathyroid hormone causing kidneys to retain Ca in blood and bone to release Ca into blood
        
        Effects include
        
        Hypercalcemia
        
        High blood & urinary Ca levels
        
        Ca deposits into soft tissue (e.g. kidney, heart, arteries)
        Which can cause irreversible organ damage
        
        When Ca levels rise above normal, rigour (no muscle relaxation after contraction)
      - Functions
        
        Bone health, formation, and maintenance
        
        Component of HYDROXYAPATITE that clusters around protein matrix (osteoid) of bone to provide strength # #
        
        Nerve transmission/muscle contraction
        
        Action potential passes along nerve cell to muscle -> open Ca ion channel -> Ca flow into muscle cells -> contraction occurs
        
        Prevent hypertension
        
        Inverse relationship when Ca intake is greater than or equal to 1000mg/day
        
        enhanced by DASH diet (low fat, high fibre, low fat dairy, moderate Na+)
        
        Blood clotting
        
        ...by being an essential component of fibrin synthesis required for blood clotting
        
        Precursors for fibrin synthesis dependent on vitamin K #
        
        Possible decrease in risk of colon cancer
        
        Possible weight loss
      - Supplements
        
        Common: carbonate, citrate, lactate, phosphate
        
        Different amounts & bioavailability of Ca per type of supplement (~30% for all supplements except citrate ~35%)
        
        Avoid “natural” source supplements (unrefined oyster shell, dolomite, coral, bone meal)
        
        ...because they are high in heavy metals (lead, mercury, cadmium) unless they have been refined
        
        Take Ca supplements....
        
        at times when there is low Ca and/or iron intake
        
        in divided doses (max. 500mg Ca/dose)
        
        everyday if reliant for adequate Ca intake
        
        before bed
        
        Decreases absorption of other minerals (ie. iron, magnesium)
      - Deficiency #
        
        Osteoporosis
        
        1 in 4 women, 1 in 8 men (50+ yrs) diagnosed in Canada
        
        can be prevented in young women, adults, and menopausal women by...
        
        Therapy (Estrogen, Vitamin D, Calcitonin, Bisphosphonate) which can be expensive and & has side effects
        
        Ensure adequate nutrient intakes of Ca, P, Mg, F, vit D & K
        
        Remain physically active, healthy lifestyle choices
        
        Quit smoking & drinking
        
        Maximizing potential for building peak bone mass early in life is crucial in reducing risk of osteoporosis later on (Ca & vit D intake)
        
        ...is a silent disease & multifactorial etiology
        
        Factors affecting the risk for osteoporosis
        
        Ca nutrition and associated nutrients (vitamin D, fluoride, excessive sodium
        
        Excess Na+, caffeine, protein intake can cause urinary loss of Ca from body (Ca(mg):PRO(g) ratio between 16:1 to 20:1 recommended)
        
        Low fluoride intake especially during infancy, childhood, youth
        
        Low levels of circulating vitamin D -> low Ca absorption
        
        Smoking & alcohol
        
        Smokers: lower body weight, earlier menopause
        Alcohol: slows bone growth, less vitamin D, increased risk
        
        Toxic to bone
        
        Underweight women
        
        increased riskfor women who are naturally light in weight or w/ anorexia nervosa
        
        Physical activity
        
        Hormones involved in muscle growth also involved in bone growth
        
        Weight-bearing & resistance exercise good for bone
        
        Age/gender/hormones
        
        Sex hormones are protective of bones, and with old age (menopause), estrogen needed to synthesize vitamin D decreases
        
        Bones strongest & most dense in young adulthood
        
        Genetics/race
        
        Heredity affects bone growth, peak bone mass, bone loss rate
        
        Decreased bone density
        
        Increased bone fragility
        
        Increased risk of fractures
        
        When Ca levels in muscle cells below normal, tetany (spasmodic relaxation)
  - - - Deficiency
        
        Low fluoride supply can lead to...
        
        increased risk of dental caries
        
        Dental problems, leading to...
        
        inability to...
        
        chew properly
        
        consume wide variety of foods
      - Toxicity
        
        Fluorosis
        
        In teeth, causes...
        
        more resistance to decay, but permanent discolouration
        
        white specks/brown streaks on teeth
        
        In skeleton, causes...
        
        abnormal hardening, joint stiffness & pain, brittle bones
        
        (possibly) osteoporosis
        
        No link to increased risk of cancer
        
        At greatest risk are...
        
        CHILDREN ingesting large amounts of toothpaste/given excessive fluoride drops
      - Functions
        
        Bone & teeth mineralization
        
        F replaces hydroxyl group in HYDROXYAPATITE creating stronger crystal FLUORAPATITE #
        
        Best taken before teeth erupt through gums
        
        Pregnancy: baby teeth forming
        
        3-4 yrs: permanent teeth forming
        
        8-10 yrs: wisdom teeth forming
        
        For adults, protective topical antimicrobial treatment
        
        Helps re-mineralize enamel lesions
      - Food sources
        
        Animal Foods: - Seafood - Shellfish -Fish (ie. sardines)
        
        Plant Foods: - Brewed tea - Seaweed
        
        Water (usually not bottled water)
        
        Non-foods: mouthwash, toothpaste, chewing gum
      - Properties
        
        Ubiquitous, found in...
        
        soils, water supplies, plant foods, animal foods
        
        Moderate (not excessive) fluoride intake can reduce dental caries
        
        Absorption
        
        30~80% bioavailability