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

Chapter 4 – Milk and dairy products as part of the diet 133
cium intake can also have a positive effect on bone mass in premenopausal women
and reduce bone mineral density loss. In older adults, the effectiveness of dairy/calcium
supplementation depends on various factors. BMD is used to define peak bone
mass in young adults and it is generally accepted to be a strong predictor of fractures
in the elderly. One limitation of BMD trials is that although a short-term increase in
BMD may be seen, effects may be transitory. Although the majority of clinical trials
with calcium or dairy-product supplementation in children and adolescents show a
positive effect of intervention on bone mass, they are generally too short to address
the question of whether it is the adaptation of bone tissue to nutritional challenge
that leads to peak bone mass. There is some evidence to suggest that advantages in
bone gains due to interventions may remain when the intervention is discontinued
if the intervention is dairy.
Osteoporosis is a condition of low bone mass with increased risk of fracture.
According to the 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. Diets with low dairy product intake have been associated
with increased risk of osteoporosis. The results from two studies suggest that milk
avoidance is associated with increased risk of fracture in children. Milk consumption
in childhood may also protect against the risk of osteoporotic fractures in
postmenopausal women. However, milk consumption during adult life does not
appear to be associated with reduced risk of fracture. Milk-product intervention in
postmenopausal women and older men who have habitually low calcium intakes
appears to protect against bone loss. Meta-analysis of RCTs of calcium with or
without vitamin D show mixed results for fracture prevention: some studies suggest
an improvement in fracture outcome with calcium (Boonen et al., 2007; Tang et al.,
2007), some show no effect (Bischoff-Ferrari et al., 2007, for nonvertebral fractures)
and some even show an increase in fractures (Bischoff-Ferrari et al., 2007, for hip
fractures). Meta-analyses of pooled prospective epidemiologic studies suggest that
calcium intake is not significantly associated with hip fracture risk in men and
women (Bischoff-Ferrari et al., 2007, 2011), although a possible benefit for men
of a higher milk intake could not be excluded (Bischoff-Ferrari et al., 2011). Most
of the evidence suggests that adequate supplies of both vitamin D and calcium are
necessary to see significant reductions in nonvertebral fractures, and those effects
may be seen only in people who have too little vitamin D or calcium (or both)
in their diets. Other lifestyle recommendations for reducing osteoporosis include
increasing physical activity; reducing sodium intake; increasing consumption of
fruits and vegetables; maintaining a healthy body weight; avoiding smoking; and
limiting alcohol intake. There is no satisfactorily answer to the question behind the
“calcium paradox”, i.e. why the vast majority of the world’s population consumes
500 mg of calcium or less per day and little or no dairy products and yet still has low
fracture rates. An overall healthy lifestyle and diet that includes adequate calcium
and vitamin D is perhaps the most appropriate recommendation. And we need
to keep in mind, as aptly stated by Nieves and Lindsay (2007), “Bone is not just
calcium, and calcium does not function in isolation”.
Calcium and/or vitamin D-deficient rickets have been reported in young children
in 59 countries. Nutritional rickets may be caused by either vitamin D or calcium
deficiency, or more often, by a variable combination of both. The final common