Milk-and-Dairy-Products-in-Human-Nutrition-FAO

Chapter 4 – Milk and dairy products as part of the diet 129
variation in the incidence and prevalence of osteoporosis is difficult to determine
because of problems with definition and diagnosis; the most useful way of comparing
osteoporosis prevalence between populations is to use fracture rates in older
people (WHO and FAO, 2003). Since osteoporosis is usually not life-threatening,
quantitative data from developing countries are scarce (WHO and FAO, 2003).
However, the consensus is that rates are many times higher in affluent developed
countries than in sub-Saharan Africa and Asia. Osteoporosis is most common
in Caucasian women living in temperate climates and least common in Africans
(WHO and FAO, 2003).
Diet appears to have only a moderate relationship to osteoporosis, but calcium
and vitamin D are both important, at least in older populations (WHO and FAO,
2003). Diets low in dairy products have been associated with increased risk of
osteoporosis: bone resorption rates increased after just six weeks of an intervention
designed to protect heart health by increasing fruit, vegetable and grain consumption
while decreasing meat and dairy consumption (which recorded significant
decreases in dairy servings per day and calcium and vitamin D from food) (Merrill
and Aldana, 2009). A meta-analysis of nine studies reported lower BMD of the
spine and hip in vegans than in those who consume milk (Ho-Pham, Nguyen,
and Nguyen, 2009). Retrospective studies show that low milk consumption (less
than one serving of milk/week) in childhood was associated with a doubling of
hip fracture in American postmenopausal women, independent of current milk or
calcium intake (Kalkwarf, Khoury, and Lanphear, 2003). However, no association
was found between adolescent milk intake and the risk of osteoporotic fractures
in these women. Higher calcium intakes throughout life (more than 800 mg/day)
were found to significantly reduce the odds of osteoporosis defined by BMD by
25 percent in relatively healthy postmenopausal Caucasian women, as did higher
current calcium and vitamin D intakes (Nieves et al., 2008). However, calcium and
vitamin D intake did not significantly reduce the odds of any fracture. The authors
ascribe a number of different reasons for this result, including insufficient power
(despite large sample of 76 507 and 2 056 new fractures in three years, there were
only 337 hip fractures), the multifactorial etiology of falls and fracture or the need
for even higher levels of vitamin D or calcium in postmenopausal women (Nieves et
al., 2008). Regular consumption of cheese and milk as well as chicken, egg, fruit and
tea was protective against osteoporosis risk in Iranian women (Keramet et al., 2008).
Milk avoidance is also associated with increased risk of fracture in children
(Goulding et al., 2004; Konstantynowicz et al., 2007). A milk-free diet (to avoid
cow-milk allergy) has been associated with increased fracture risk in girls (Konstantynowicz
et al., 2007), although the authors reported that it is unclear if this
association is due to the illness, calcium deficit or a deficit in other milk nutrients.
Based on their results, the authors concluded that the contribution of milk-free diet
to fracture liability among children and adolescents is modest. In another study, 50
children (3–13 years) who had avoided drinking cow milk for prolonged periods
were compared with those in a birth cohort of more than 1 000 children from the
same city (Goulding et al., 2004). Children who avoided milk did not use calciumrich
food substitutes appropriately and had low dietary calcium intakes and low
BMD values, and many were overweight. Significantly more of the milk avoiders
experienced more total fractures than the birth cohort population, all of the frac-