Bone and Calcium Metabolism: Prevention of Osteoporosis

Bone metabolism in the human body is a veryemphasis has been place on sunscreen, there is less
dynamic process.  There is a constant lying down ofsun effect and a greater need for vitamin D
bone by cells called osteoblasts and resorbtion ofsupplement.  The exact amount of vitamin D
bone by cells called osteoclasts.  Initially therequired is being debated, but the consensus is that
osteoblasts work much harder and faster that theAmericans are generally deficient in vitamin D and
osteoclasts and bone is laid down to facilitate growth.require greater amounts than originally thought.  800
Each person has a genetically determined peak boneinternational units to 1000 international units is the
mass which is attained in their twenties.  By age 17current recommendation for adults.
ninety percent of the bone mass has beenCertain medical conditions may limit the amount of
obtained.  The consequence of bone loss is thecalcium that may be ingested.  As always, consulting
development of very weak and fragile bones, ayour physician is suggested regarding your personal
medical condition known as osteoporosis. specific calcium needs.
Osteoporosis is associated with compression fracture
of the bones of the spine called vertebra(ae) andExercise is Necessary to Maintain Bone Health
fracture of the hip.  While these fractures fromWeight bearing exercise (walking, running, etc.) is an
osteoporosis may be painful and cause shortening ofexcellent stimulus for bone growth.  Current
stature, even difficulty breathing, the majorrecommendations are:
consequence is complications and even death fromAdults: Engage in at least 30 minutes of moderate
surgical repair of the hip fracture.physical activity [on] most, preferably all, days of the
Calcium and Vitamin D Play a Critical Roleweek
Adequate calcium, exercise and vitamin D areChildren: Engage in at least 60 minutes of moderate
required to attain and maintain bone mass. This isphysical activity [on] most, preferably all, days of the
important in the prevention of osteoporosis.  Currentweek
data indicates that the majority of children do notBone Mineral Density
receive adequate amounts of calcium or vitamin D.The evaluation of bone strength, the about of
Recommended amount of calcium vary for individuals.calcium in the bone, is measured by a dual density
Below is a table of adequate intakes as outlined bydensitometer.  The purpose of this is to measure
the National Academy of Science.the exact bone mineral density of the spinal
Recommended Calcium Intakesvertebrae, usually the four lumbar (lower back)
Ages    Amount mg/dayvertebrae, and the femur, the large thigh bone that
Birth–6 months    210connects to the pelvis in the hip socket.  
6 months–1 year    270The bone mineral density (BMD) is usually expressed
1–3    500as a “T” score which is a comparison of the
4–8    800patients BMD to a young person.  A “T”
9–13    1300score that is - 1 or higher is considered normal.  A
14–18    1300“T” score of - 2.5 or lower is considered
19–30    1000osteoporosis.  A “T” score between – 1
31–50    1000and – 2.5 is called osteopenia – a softening of
51–70    1200the bone.
70 or older    1200Bone mineral density testing should be recommended
Pregnant & Lactating    1000to all postmenopausal women aged 65 years or
14–18    1300older.  Bone mineral density testing may be
19–50    1000recommended to postmenopausal women younger
Role of Vitamin Dthan 65 years who have 1 or more risk factors for
Vitamin D also plays an important role in healthy boneosteoporosis (See Below). Bone mineral density
development. Vitamin D helps in the absorption oftesting should be performed on all postmenopausal
calcium (this is why milk is fortified with vitamin D). women with fractures to confirm the diagnosis of
In the past many people depended on the sun’sosteoporosis and determine disease severity.
effect on the skin to make vitamin D.  Since more