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Caucasian women (termed a T-score ment; that is, such individuals did approximately 30 years old, the WHO
of -2.5).4 This was a milestone in not achieve an average or “normal” terms osteopenia or osteoporosis
prevention because it allowed diag- bone mass at skeletal maturity. The should not be applied; doing so
nosis in an asymptomatic state prior maximal mass of bone achieved is simply leads to unnecessary anxiety
to fracture. Subsequently, a number important because the amount of and potentially to unnecessary diag-
of pharmaceutical agents including bone at any age reflects all events, nostic evaluation. Instead, the correct
estrogen, raloxifene, bisphosphonates, both positive and negative, that have interpretation of lower-than-normal
and calcitonin have proven efficacy happened during a person’s life. This bone mass in young individuals is
in reducing future fracture risk among phenomenon is depicted in Figure 1, “failure to attain average bone mass.”
individuals diagnosed with osteo- which shows that the great majority
porosis on the basis of low BMD.5 of skeletal mass is attained prior to age Role of Nutrition in Bone Mass
20, with a subsequent small increase
Pathophysiology until approximately age 30. Many of Approximately 70 percent of peak
the above noted factors may impair bone mass is genetically determined.
In most people, there is no one “cause” accrual of an individual’s full genetic However, environmental factors may
of osteoporosis, because this is a potential. As such, less bone loss adversely affect whether this inherited
multifactorial disease caused by a needs to occur before skeletal fragility peak is attained. One such factor is
combination of nutritional insuffi- manifests. This underscores the criti- low calcium intake. Unfortunately,
ciencies (classically, low calcium and cal importance of childhood and the median daily intake for girls (9–
vitamin D intake), inactivity, skeletal adolescence on future risk for low 17 years old) is 681–801 mg and for
toxins such as tobacco and excess trauma fracture; in fact, osteoporosis boys (9–17 years old) is 996–1,026
alcohol, sex steroid deficiency, advanc- has been called a pediatric disorder mg, whereas the recommended intake
ing age, and certain prescription that manifests itself in old age.6 is 1,200–1,500 mg. The magnitude
medications, notably corticosteroids. of this calcium insufficiency is made
Additionally, female sex and a family It should be noted that the WHO clear when one considers that ~90
history of low-trauma fracture are osteoporosis criteria were designed for percent of girls age 9 to 18 years fail
often cited as osteoporosis risk factors. individuals who have attained peak to ingest three fourths of the recom-
In reality, these last two factors likely skeletal mass. As such, if BMD is mended intake.7 Furthermore, adoles-
reflect low peak bone mass attain- measured in individuals younger than cent athletes sometimes deliberately

Figure 1: Diagrammatic repre- Full Genetic Potential Menopause
sentation of the bone mass life-
line in individuals who achieve Inadequate High
their full genetic potential for Environmental Fracture
skeletal mass and those who do Factors Risk
not. Note that the magnitude of
the difference between curves BONE MASS
is not intended to be to scale.
Along the bottom are several
of the factors known to be of
particular importance. Reprinted
with permission of Robert P.
Heaney, Copyright 1999.

0 10 20 30 40 50 60 70
AGE

HEREDITY
EXERCISE/LOADING

CALCIUM & VITAMIN D INTAKE

THE ROLE OF BONE MASS IN OSTEOPOROSIS 135
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