Lecture 12 - Nutrients for Bone Health Flashcards Preview

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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?



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


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:
1. Inhibits activation of vit D
2. Prevents Ca reabsorption in kidneys
3. Limits Ca absorption in intestines
4. 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:
1. Causes kidneys to retain more Ca
2. Osteoclasts to break down bone and release Ca
3. 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


What are sources of Ca?

Tiny fish with bones


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