10. Nutrients Involved in Bone Health Flashcards
Describe bone structure.
Trabecular bone:
- less-dense, more open structure
- found in inner layer of bones
Cortical bone:
- compact or dense bone
- found on outer surfaces of bone
Bone marrow:
- spongy tissue
- in flat bones and trabecular bones
- contains stem cells
Periosteum:
- connective tissue covering all bones
- has bone-forming potential
Describe the process of bone growth and remodelling.
Osteoclasts:
- bone marrow breaks down or degrades small amounts of bone
Resorption:
- losing substance: part of initial process for remodelling and growth
Osteoblasts:
- bone cells that initiate synthesis of new bone
Hydroxyapatite:
- crystalline compound containing calcium, phosphorus, sometimes fluoride, also known as bone mineral
Osteocyte:
- osteoblast embedded into the bone matrix
Bone mineral density:
- measure of the amount of total mineral contained in a certain volume of bone; generally expressed as grams/cubic centimeter
Peak bone mass:
- achieved by age 30
Bone resorption:
- occurs at rate faster than bone synthesis after age 30; leads to decrease in bone mass and bone mineral density
Bone composition:
- 65% minerals; 35% connective tissue
List biological and lifestyle factors that influence bone health.
Biological:
- sex; age; race; frame size, estrogen
Lifestyle:
- healthy body weight; normal menses; movements that create impact and muscle loading forces on bone; smoking; medications; excessive intake of protein, sodium, alcohol, or caffeine; inadequate UV-B exposure
List sources and functions of calcium, including its role in bone growth, maintenance, and repair.
Functions:
- bone growth, maintenance, and repair: 99% of calcium is used
- muscle and nerve function
- regulation of cellular metabolism
Sources:
- dairy products
- fat-free milk
List the functions, recommendations, and sources of phosphorus.
Function:
- component of hydroxyapatite
- part of DNA and RNA
- primary component of ATP
- allows enzymes and B vitamins to function
- component of phospholipids membrane
- maintains blood pH and fluid balance
Recommendations:
- RDA: 1250 mg, 9-18 years; 700 mg, adults
Sources:
- naturally abundant foods
- milk, cheese, meat, and bread
- nuts, fish, cereal, bran, eggs
List sources and functions of vitamin D.
Binds to and affects cells of:
- immune system
- brain and nervous system
- parathyroid gland
- pancreas
- skin
- muscles
- reproductive organs
Regulator of cell growth:
- skin
- colon
- prostate
- breast
May decrease certain types of cancer risk.
Sources:
- fatty fish
- dairy foods
- cereals
- mushrooms
Explain vitamin D and its synthesis in the skin by the action of ultraviolet radiation.
Skin:
- 7-dehydrocholesterol: converted to vitamin D3 by sunlight exposure
Liver:
- vitamins D2 and D3: converted to 25-hydroxyvitamin D3 (calcidiol) (main form found in blood)
Kidney:
- calcidiol: chemically converted to 1.25-dihydroxyvitamin D3 (calcitriol)
List signs and symptoms of vitamin D deficiency.
Risk in:
- dark-skinned
- low vitamin D diet
- exclusively breastfed infants
- elderly
- insufficient sun exposure
- diet without fortified foods
With lower levels of vitamin D:
- osteomalacia
- intestinal calcium absorption decreases
- rickets
List the functions and sources of magnesium.
Functions:
- provides bone rigidity
- nerve and heart function
- muscle relaxation after contraction
- assits in 300+ enzymatic reactions
- resistance to tooth decay
- lower risk of type 2 diabetes
Sources:
- chlorophyll
- vegetables
- milk and meats
- chocolate
- tap water
Describe the role of fluoride in tooth development and bone health.
List some primary sources of fluoride.
- marine fish, clams, lobster, shrimp
- tea
- seaweed
- some natural water sources
- dental products
List other nutrients involves in bone health and describe their primary functions.
Vitamin C:
- promotes bone health through its antioxidant activity
Iron:
- required by enzyme that converts vitamin D to active form
Zinc:
- cofactor for enzymes of bone remodelling
Copper and Silicon:
- contribute to collagen synthesis
Vitamin K:
- calcium-binding ability to bone proteins
Boron:
- bone structure and strength
Describe the process of osteoporosis development and prevention.
- low bone mass
- deterioration of bone tissue
- fragile bones leading to bone fractures
- shortening and hunching of the spine
Prevention:
- build maximally dense bones
- age
- gender
- physical activity
- diet
- lifestyle factors
Describe current methods used to assess bone health.
Dual energy x-ray absorptiometry (DEXA):
- takes less than 15 minutes
- bone blocks path of low-level x-ray
- normal bone density is 0 to -1 score
- low bone density is -1 to -2.4
- osteoporosis is -2.5 or lower
Fracture risk assessment tool (FRAX):
- less expensive online tool to test risk of fracture
List causes of calcium deficiency.
- kidney diseases, hormonal abnormality, or medications
- if blood calcium falls below a critical point, muscle cannot relax after contraction and nerve function is disrupted
- result is tetany which muscles become stiff or twitch involuntary
