CHAPTER 9Nutirent Involved in Bone Health
How Does the Body Maintain Bone Health?
Bones are living organs that contain:
o Several tissues (including bone tissue)
o Connective tissue
Bone Composition and Structure Provide Strength and Flexibility
65% of bone tissue is make up of many minerals (mostly calcium and phosphorus)
that provide hardness
35% of bone is a mixture of organic substances that provide strength, durability, and
o The most important substance is collagen
Minerals form around the collagen fibresthis design enables bones to
bear weight while responding to movement
CORTICAL BONE (COMPACT BONE) - a dense bone tissue that makes up the outer
surface of all bones, as well as the entirety of most small bones of the body.
o Makes up 80% of our skeleton, contains microscopic openings that serve as
passageways for blood vessels and nerves.
o The outer surface of all bones is cortical
o Small bones (wrist, hands, and feet) are made of cortical
TRABECULAR BONE (SPONGY or CANCELLOUS BONE) - a porous bone tissue
that makes up only 20% of our skeleton and is found within the ends of the long
bones, inside the spinal vertebrae, inside the flat bones (breastbone, ribs, and most
bones of the skull and inside the bones of the pelvis.
o Makes up 20% of our skeleton
o Found within:
The ends of long bones (arms and legs)
Inside the spinal vertebrae
Inside flat bones (breastbone, ribs and most bones of the skull)
Inside the bones of the pelvis
o The bones is aligned in a precise network of columns that protects the bone of
o Has a faster turnover rate than cortical bonemore trabecular bone is being
broken down and replenished at any given time
o More sensitive to changes in hormones and nutritional factors
The Constant Activity of Bone Tissue Promotes Bone Health
Bone develops in a series of three processes
o Bone growth
Determines bone size
Begins in the womb
Continues until early adulthood
o Bone modelling
Determines bone shape
Begins in the womb
Continues until early adulthood
o Bone remodelling NUTR*1010FINAL
Maintains integrity of bone
Replaces old bone with new bone to maintain mineral balance
Involves bone resorption and formation
Occurs predominantly during adulthood
Bone Remodelling Maintains a Balance Between Breakdown and Repair
BONE DENSITY- the degree of compactness of bone tissue, reflecting the strength
of the bones. Peak bone density is the point at which a bone is strongest.
o Peak bone density occurs when boys are 14, and girls are 12.5 years old.
REMODELLING- the two-step process by which bone tissue is recycled; includes the
breakdown of existing bone and the formation of new bone.
o Repairs bones that have been broken or damaged
o Strengthen bone regions that are exposed to higher physical stress
RESORPTION- the process by which the surface of bone is broken down by cells
o OSTEOCLASTS- cells that erode the surface of bones by secreting enzymes
and acids that dig grooves into the bone matrix.
o Bones are broken down to:
Release calcium into the bloodstream
To help smooth rough edges from a break in the bone
OSTEOBLASTS- cells that prompt the formation of new bone matrix by laying down
the collagen-containing component of bone that is then mineralized.
Around 40 years of age, bone resorption beings to occur more rapidly than bone
formationresults in overall loss in bone density
How Do We Assess Bone Health?
Dual Energy X-Ray Absorptiometry Provides a Measure of Bone Density
DUAL ENERGY X-RAY ABSORPTION (DXA or DEXA)- currently the most accurate
tool for measuring bone density.
o 15mins for a scan of the hip and lower spine
o 30mins for a full body scan
o Recommended for postmenopausal women
T-SCORE- a composition of individuals bone density to the average peak bone
density of a 30-year-old healthy adult of the same sex and race. If bone density is
normal, the T-score will be between +1 and -1.
o Score between -1 and -2.5, person has osteopenia (increased risk of fractures)
o More than -2.5, person has osteoporosis
o +1 and -1, is normal
o More then +1, better than normal bone mass
Other Bone Density Measurement Tools
Quantitative ultrasound technique
o Uses sounds waves to measure the density of bone in heel, skin, and kneecap
Peripheral dual energy x-ray absorptiometry (pDXA)
o Measures bone in peripheral regions of the body including wrist, heel or finger
Single energy x-ray absorptiometry
o Measure bone density at the wrist or heel
A Profile of Nutrients That Maintain Bone Health
Calcium composes 2% of our entire body weightNUTR*1010FINAL
Functions of Calcium
99% of calcium is stored in our bones
1% is found in the blood and soft tissues
Calcium and phosphorus crystallize to form hydroxyapatite
The skeleton not only provides physical support to our bodiesit also acts as a
storehouse for calcium to assist in the regulation of blood calcium
Calcium is critical for the normal transmission of nerve impulses
o Calcium flows into nerve cells and stimulates the release of molecules called
neurotransmitters, which transfer the nerve impulses from one nerve cell to
When blood calcium level dangerously fall, one can experience
Table 9.2 Nutrients Essential to Bone Health
How Much Calcium Should We Consume?
The Adequate Intake (AI) for Calcium is:
o Adults 19-50 years: 1000mg/day
o Adults over 50 years: 1200mg/day
o Boys and Girls 15-18 years: 1300mg/day
The upper level (UL) for calcium is 2500mg/day for all ages and gender groups
BIOAVAILABILITY- the degree to which our bodies can absorb and use any given
The ability to absorb calcium diminishes with age, can be as low as 25%