NUTRITION WEEK 10 – BONE HEALTH
Bones are dynamic, living organs; they have many important roles in the body and it is important to maintain them.
FUNCTION OF BONES
Structure and Support Metabolic Processes
• Structural support for organs and body • Bone tissue acts as a storage reservoir for
segments many minerals including calcium,
phosphorus and fluoride; the body draws
• Bones protect our vital organs ex. the rib • Production of blood cells in bone marrow
cage protects our lungs
• Muscle support for movement; muscles
attach to bones via tendons
Minerals 65%; provides hardness; mostly calcium and phosphorus.
Organic substances 35%; provides strength, durability and flexibility; collagen (a fibrous protein)
Major roles: calcium, vitamin d, Vitamin K Minor roles: magnesium, phosphorus, vitamin A, protein, fluoride
Growth: determines bone size; begins in womb and continues until early adulthood
Modelling: determines bone shape; longitudinal growth, continues into early adulthood
Remodelling: maintains bone balance between breakdown and repair; recycling the bones; bone resorption and
Resorption: breaking down of the bone; osteoclasts – cells that erode the bone surface by secreting enzymes
and acids that dig grooves into the bone matrix; minerals become released into the bloodstream.
Bone formation: new bone is formed; osteoblasts – “bone builders”; synthesize new bone matrix by laying down
the collagen containing organic components of bone; new bone is created where it is needed.
Peak bone mass: highest amount attained during the years of normal bone growth; ends during adolescence or late 20’s;
influenced by nutrition, exercise, disease, drugs.
MEASURING BONE STATUS
Dual Energy X-ray Absorptiometry (DXA)
Measures bone density; or BMD; can determine risk for osteoporosis and monitor changes in BMD; use T-score and
compare to average person.
+1.0 normal bone density -2.0 low bone mass (osteopenia) -4.0 presence of osteoporosis Osteoporosis
Most prevalent bone disease in North America; characterized by low bone mass and deterioration of bone tissue;
leading to enhanced bone fragility and increased fracture risk; weaken the bone and reduce ability to bear weight.
Modifiable: nutrition, medications, physical activity; smoking, low body weight, alcohol abuse, repeated falls, hormone
deficiencies; medications; estrogen/testosterone deficiency; low sun exposure
Non-modifiable: age, gender, genetics, Caucasian or Asian race; histories of falls; amenorrhea (failing to menstruate).
Age risk increases with age; BMD gradually decreases with age and creates imbalance in remodelling;
Gender women have a higher risk than men; lower bone density and longer life expectancy; low estrogen
causes more bone resorption and less bone formation; without estrogen, bone remodelling is uneven; lower bone
MINERALS AND BONE HEALTH
- A major mineral we need 100mg per day; most abundant mineral in the body and it makes up 2% of our body
- 99% of calcium in stored in bones; critical part of hydroxyapatite crystals that provide strength to the bones.
Electrolyte: other 1% of calcium is in the blood as an electrolyte; it regulates heartbeat, blood clotting, normal
functioning of nervous system, muscle contraction and relaxation; the body controls blood levels of calcium closely.
Your body will take what it needs from your bones and the blood level will not change but your bones will weaken.
RDA’s from DRI’s for Calcium:
Age Men Women
13-18 1300mg/d 1300mg/d
19-50 1000mg/d 1000mg/d
51-70 1000mg/d 1200mg/d
70+ 1200mg/d 1200mg/d Sources of Calcium
- Milk and milk products are number one source of
calcium in Canadian diet (calcium fortified orange juice, soy
- fish eaten with bones (canned salmon, sardines)
- Some nuts (almonds) and seeds (sesame)
- Dark green veggies (kale, bok choy, broccoli)
Food Serving Calcium Absorption Amount
per rate (%) of calcium
Yogurt 1 cup 452mg 32 145
Milk 1 cup 300mg 32 95
Kale 1cup 179mg 59 106
Broccoli 1 cup 61mg 61 37
Spinach 1 cup 290 mg 5 15
Best vegetable: Kale; you need three cups of cooked broccoli (6 servings) to get as much calcium as in 1 cup of milk.
- Your intestines only absorb 1 cup of milk’s worth of calcium at one time; spread out your calcium throughout
the day; oxylates (spinach), phytates (whole grains) and tannins (tea) decrease absorption.
- Avoid taking zinc, iron or magnesium supplements when you’re eating a source of calcium.
DRI’s take absorption into account*
Vegans and dairy free people
Best dairy free sources: milk alternative (soy, rice, almond or coconut milk, yogurt or cheese); high calcium leafy greens;
tofu; almonds and sesame seeds; consume everyday.
What to do if deficient
Things to consider in selecting a supplement:
- Amount: you cannot absorb more than 500 mg at a time
- Form of supplemen