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It's a common notion that milk makes bones stronger; milk contains calcium and bones contain calcium. But obviously it's not the case that calcium ingested is immediately deposited into bones. In fact, there seem to be no studies suggesting this at all. On the contrary, here is a study published 2015 that finds no association between milk intake and bone fractures. And here is an excerpt from PCRM:

Research shows that dairy products have little or no benefit for bones. A 2005 review published in Pediatrics showed that drinking milk does not improve bone strength in children. In a more recent study, researchers tracked the diets, exercise, and stress fracture rates of adolescent girls and concluded that dairy products and calcium do not prevent stress fractures.

  • Nowadays you're hearing the exact opposite: milk allegedly causes osteoporosis. There's already a question on here about that. – aross Nov 8 at 13:02
  • Calcium also comes from water, clay and rock, vhesper than milk which has more lobbying power than mineral sources. you dont need much as an adult. Conditions that cause a low pH like lots of sugar and cola are not good for some old people with bone conditions. Magnesium is a more common diffucience. – com.prehensible Nov 8 at 21:12
  • @aross there was actually a large study in Sweden in which, high milk consumption was associated with higher incidence of fractures, especially in women. The authors suggested that one possible explanation is reverse causation: women with higher risk for osteoporosis (for example, due to family history of osteoporosis) drink more milk to prevent osteoporosis but they still develop it - so, it may be not that milk causes osteoporosis. – Jan Nov 9 at 10:02
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    It's not about what effect milk has; we need a source of calcium in a form our bodies can use, in sufficient quantity to meet need. Our needs vary with age and condition. We don't just need calcium, but also other micronutrients including vitamin D so that the body can use the calcium we ingest. Milk happens to offer a supply of calcium, not necessarily useful by itself. Normal processes are also constantly removing calcium from bone because our bodies have other uses for it besides bone structure; it is part of the electrochemical processes involved in nerve signaling. – Anthony X Nov 9 at 18:05
  • Milk also contains protein, which interferes with the absorption of calcium. – WGroleau Nov 10 at 2:44
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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.

Basic explanation:

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):

However, 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)

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    Well, as adults, they might feel better about drinking milk. How much does the placebo effect has on a person is highly debatable... – Nelson Nov 8 at 2:54
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    @Nelson That's not debatable at all. The placebo effect is well known and studied. – Stian Yttervik Nov 8 at 7:05
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    The placebo effect, sure. How about placebo effect of drinking milk on bone growth? I've never heard of that being studied ;) – Nelson Nov 8 at 7:11
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    @Nelson Because that doesn’t really make sense, and relies on a misunderstanding of the term “placebo”. The placebo effect is in general not an actual biological effect, it describes subjective interpretation of an effect. Bone density isn’t subjective, it’s measurable, and thus not affected by a placebo effect. Studies where placebo effect plays a big role always have a highly subjective component: usually it’s pain perception, but it can also affect (appearance of) recovery rate as well as actual effects caused by stress. – Konrad Rudolph Nov 8 at 15:47
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    @KonradRudolph I seem to recall that a person "feeling" positive about their health actually had a positive impact on their health and that "feeling" negative on their health caused negative effects to the health. This had something to do with neuro pathways sending signals to various parts of the body (open & sending good signals means faster healing, closed means slow to no healing, open & sending bad signals means degeneration). If indeed true, the placebo could make a person think they should feel positive, thus they feel positive, thus they have a positive effect on healing & growth – wolfsshield Nov 8 at 17:28

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