Lecture 12 - Nutrients for Bone Health Flashcards
What are the nutrients involved in bone health?
Ca, P, Vit D, Mg, F, Vit K
What is the breakdown of bone material?
65% Mineral crystals
35% Organic substances
What is the difference between mineral crystals and organic substances in bone?
Mineral is for strength and structural support
Organic made of collagen and hydroxyapatite
What is the purpose of hydroxyapatite?
For flexibility
Ca and mineral reserve
High turnover
What are bones made of?
Cortical: dense outer wall of larger bones and 100% of small bones
Trabecular: lattice inside the bone adding strength without weight. Influenced by hormones and environment
What are some bone functions related to the metabolic process?
Bone tissue acts as storage reservoirs for m minerals
Most blood cells are produced I the bone marrow
What are the 3 stages of bone growth?
Bone growth
Bone modelling
Bone remodelling
When does bone growth stage start and stop?
Increasing length of bones starts in conception and stops at 14yr (girls) and 17yr(boys)
When does bone remodelling start and stop?
Starts at conception with laying down additional bone density
-density accrues at the same time into young adulthood
When does bone remodelling start and stop?
It is a life long process involving osteoclasts and osteoblasts
What is the age of peak bone density?
Age 20-30
What are the 3 processes that bone remodelling entails?
Resorption: surface bone is broken down
–> osteoclasts are cells that erode surface of bones
Formation of new bone by osteoblasts
–> osteoblasts produce collagen containing component of bone
What do osteoclasts resemble when they are doing their job?
They act as scrubbers and scrub the bone down releasing minerals into the blood
What is the most abundant mineral in the body?
Ca
Where is most Ca found in the body?
99% in bones
-forms a matrix on collagen
strength and rigidity
-continuous remodelling
1% body fluids
- extra and intracellular compartments
- different functions
What tool do we use to assess bone health?
Dual-energy x ray absorptiometry (DXA or DEXA)
-most accurate way to measure bone density
How does the DEXA work?
- Uses very low level x ray energy
- Full body scan but can be used for specific areas
- noninvasive
How do you interoperate DEXA results?
T score obtained is compared to that of a 30yo woman
- within 1 standard deviation is normal
- between 1-2 at risk
- between 2-3 osteoperosis
What are the other roles of Ca?
- Forms and maintains bone and teeth
- Acid-base balance
- Transmission of nerve impulses
- assists in muscle contraction
How does the body deal with high levels of blood Ca?
Thyroid releases calcitonin which functions to:
- Inhibits activation of vit D
- Prevents Ca reabsorption in kidneys
- Limits Ca absorption in intestines
- Inhibits osteoclasts cells from breaking down bone preventing the release of Ca
How does the body deal with low levels of Ca?
Parathyroid Hormone is released to stimulate the activation of vitamin D which:
- Causes kidneys to retain more Ca
- Osteoclasts to break down bone and release Ca
- Stimulation of Ca absorption from intestines
What is the RDA for Ca?
Varies with age and life cycle stages
- 1300mg/day (9-18)
- 1000mg/day (19-50)
- 1200mg/day females (51-70)
- 1200mg/day (71+)
Why do Ca requirements increase with age?
Reabsorption decreases as you get older so need to increase intake to make sure you absorb enough
How well do we absorb Ca?
Adults 30%
Pregnancy 50%
Children 50-60%
What does Ca absorption depend on?
-bioavailability of Ca
Enhancers: Stomach acid, vit D
Inhibitors: Lack of enhancers, high P, phytates, oxalates, fibre
What is the down fall of having Ca, phytates and oxalates together?
Phytates and oxalates inhibit Ca absorption
-mostly found in plants
What happens when you are deficient in Ca?
Low bone mineral density
Osteoperosis
What are sources of Ca?
Dairy
Tiny fish with bones
Soy
Is spinach a good source of Ca?
It is, but it also has a lot of oxalates(binders) as well which inhibits the absorption of Ca
What happens when you consume too much Ca?
- Excreted from the body
- Supplements lead to mineral imbalances
- Hypercalcemia–> can be casted by cancer or overproduction of PTH
What happens when you don’t consume enough Ca?
Hypocalcemia
-caused by kidney disease or overproduction of PTH
What kind of solubility Is Vitamin D and where is it stored?
Fat soluble
Excess stored in liver and fat tissue
How is vitamin D made?
Made by the body by exposure to UV light from the sun
What is vitamin D also considered?
A hormones because it is made in one place and acts in another location
What is vitamin D’s role in the body?
PTH stimulates activation of vitamin D which stimulates:
- Ca reabsorption in kidneys
- Enhances Ca absorption in intestines
- Osteoclast cell
How is vitamin D made?
In specialized skin cells on the top layer
-proper skin, UV sun, body heat, liver and kidneys all need to be functioning properly to mad vitamin D
How is vitamin D transformed in the body?
Vitamin D from sun or food, transformed to Calcidiol in liver, transformed to Calcitriol in the kidneys
What is the RDA for Ca?
Recommendations are based on no Vitamin D synthesis from the sun
- RDA= 600IU/day adults
- 800IU fro 70+
What is the Ca recommendation through sun?
Exposure 5-10 min 3x/wk
What does a vitamin D deficiency look like?
Rare but when it happens common among dark skin, breastfeeding without supplementation, consuming non-fortified milk, fat malabsorption
Rickets in children
What is Rickets?
Growth retardation, bone abnormalities. Bowed legs and beaded ribs
Who is at risk for vitamin D deficiency?
Elderly because they have a low intake, reduced ability to convert, reduced sun exposure
What is the diffrerence between osteoporosis and osteomalacia?
Osteomalacia is the softening of the bone, also painful and is also a decrease in bone mass
What is the Ca intake of Canadians like?
Inefficiency is common but deficiencies are still rare
What is the most likely nutrient to get a toxic rxn from?
Vitamin D
What are the toxic effects of vitamin D?
- Hypercalcemia
- Calcification of other tissues
- Kidney stones
- Hardening of blood vessels
What is the second most abundant mineral in the body?
Phosphorus in the form of phosphate
-intracellular electrolyte
What is the functions go phosphorus?
- Combines with Ca to form hydroxyapatite in bones
- Fluid balance
- Membranes
Why does P bind Ca?
To add strength to bones
What is the RDA for P?
700mg/day
-Most people get too much
What are food sources of P?
Found in protein containing foods
Can you be deficient or become toxic from P?
Deficiency is rare
UL is set to prevent kidney disease (antacid overconsumption)
What is the downfall of having too much P in the body?
It causes a decrease in Ca absorption
Where is Magnesium found in the body?
50-60% forund in bones
-also in muscle and soft tissue
What is Mg purpose in the body?
Acts as a reservoir for blood
-involved in immune system, energy metabolism, muscle contraction and blood clotting
What is Mg role in heart function?
Deficiency in Mg can result in vessel wall constriction
-increase in hard water = low rates of heart disease
What is the RDA for Mg?
Varies with age and gender due to reduced absorption with aging
What are some Mg sources?
Usually found with protein
Pumpkin seeds
Whole grains (before processed)
How might Mg be absorbed better?
when consuming Mg and protein together
What happens when you consume too much Mg?
No toxicity from Mg in foods (only through people taking supplements)
Mg supplements can cause diarrhea, nauseas, cramp, dehydration, C cardiac arrest
What happens when you do not consume enough Mg?
Hypomagnesemia: can result in low blood Ca and osteoporosis
Where do we find Fluoride in the body?
99% is in teeth and bones
trace mineral
How does F work in bone mineralization?
Replaces OH group in hydroxyapatite to make fluoroapatite. Making bones stronger and teeth more resistance to decay
What is the RDA for F?
No RDA
AI varies with gender and increases with age
- 1-4mg/day
What are sources of F?
Fluoridated dental products and water (city)
What is vitamin K used in the body for?
Blood clotting Anti-coagulation Bone health -metabolizes osteocalcin -binding Ca to bone
Where is Vitamin K made and stored?
Made in the Large intestine by bacterial and stored in the liver because it is a fat soluble molecule
Can you become deficient or toxic from vitamin K?
Deficiencies are rare
-Newborns need vitamin K shot because breastmilk doesn’t have it and their gut bacteria haven’t developed enough to make it
What are sources of vitamin K?
green veggies
vegetable oil
Which nutrients do we consume too much and too little of?
Too much: P
Too little: Ca, Mg, Vit D
