A summary of recent evidence suggests:
- In children with initial low calcium intake, an increase in milk/dairy intake is associated with an increase in bone density.
- In adults, milk/dairy consumption is not or only weakly associated with lower risk of bone fractures.
90% of peak bone mineral density (the amount of calcium and phosphorus in a volume of bone) is acquired by age 18 in women and by age 20 in men (NIH.gov). So, by intake of dairy and other foods high in calcium before age 18-20 you may somewhat increase bone density, but high calcium intake after that age will not likely help you decrease the risk of bone fractures (BMJ, 2015) or osteoporosis (BMJ, 2015).
Differences between milk and other dairy:
In the studies, the intake of neither "milk" nor "dairy" (milk + any of other milk product) was associated with increased bone mineral density or decreased risk of fractures, which suggests that other dairy products, such as cheese, are not likely to be more effective, regardless of their calcium, vitamin D, protein or other nutrient content.
Milk/dairy consumption and bone mineral density in CHILDREN and ADOLESCENTS
Milk/dairy consumption may improve bone mineral density in children and adolescents with low bone mineral density and low calcium intake.
Effects of Dairy Products Consumption on Health: Benefits and Beliefs (Calcified Tissue International, 2016):
The beneficial effects of calcium and dairy products on bone mineral
mass during growth in children are supported by meta-analyses of
numerous clinical studies on milk-derived calcium phosphate
supplementation and increased dietary dairy products, with a
statistically and clinically higher gain of bone mineral content in
those with low basal calcium intake [41, 42]. This significant
increase in bone mass following calcium enrichment of the diet
observed in pre-pubertal girls and boys [43, 44] was maintained for
1–3 years after the end of the trial [44, 45], suggesting a possible
optimization of peak bone mass when calcium supply is sufficient.
They have found a similar association in another review: Impact of dairy products and dietary calcium on bone-mineral content in children: results of a meta-analysis (Bone, 2008).
Milk/dairy consumption and bone fractures in ADULTS
Milk/dairy consumption in adults is not or only weakly associated with lower risk of bone fractures.
Dairy product consumption and risk of hip fracture: a systematic review and meta-analysis (BMC Public Health, 2018):
the consumption of total dairy products and cream was not
significantly associated with the risk of hip fracture. There was
insufficient evidence to deduce the association between milk
consumption and risk of hip fracture.
Other systematic reviews in which they have found no or only weak association between milk/dairy consumption and bone fractures:
They have found such an association in another review: Dietary Patterns in Relation to Low Bone Mineral Density and Fracture Risk: A Systematic Review and Meta-Analysis (Advances in Nutrition, 2019)