After a long argument with the same fundamentalist vegan, I dug up a couple of summaries for the entirety of the studies on bone density and dairy. There are about 100 plus studies, so I’m restraining myself and simply posting the papers that provide a statistical overview… This one has the clearest summary.
Dairy and Bone Health
About half of the volume of bone material is protein. Bone remodeling involves the synthesis of new protein matrix and requires an ongoing supply of fresh dietary protein if bone removed during resorption is to be replaced. Dietary protein has been shown in some studies to increase urinary calcium excretion; however this may be problematic only in those with low calcium intakes . Most studies indicate that dietary calcium and protein interact constructively on bone so long as the intake of each is at least adequate [31–33]. Studies have reported a positive relationship between protein intake and BMD , reduced incidence of fracture [35–38], and reduced rate of bone loss [35,39]. Dietary protein stimulates insulin-like growth factor I (IGF-I) production, which is important in bone growth [31,32]. Elderly patients with hip fractures were shown to have low serum protein levels, with improvements in outcomes seen with protein supplementation [40,41]. A study by Dawson-Hughes and Harris in 342 healthy men and women aged 65 and older found that, in participants supplemented with calcium and vitamin D over three years, those with higher protein intakes had improved total body and femoral neck BMD compared to unsupplemented subjects . The interaction of protein and calcium has been discussed in greater detail elsewhere , and the role of protein itself has been recently reviewed by Conigrave et al. [33
Heaney also reported that of 86 observational studies, 64 reported relationships in favor of increased calcium intakes, with reduced fracture risk, bone loss or improved bone mass. Additionally, of those studies specifically evaluating dairy sources of calcium, approximately 75% supported the conclusion that increased calcium from dairy foods is protective of the skeleton. After submission, but before publication, 13 additional studies were published, all 13 reported positive effects of calcium on bone health . Since then, more than 100 additional studies have been published, with the proportions of positive and null studies remaining at about 75–80% and 20–25%, respectively.
And that, is basically it. 80% of studies find dairy strengthens bones. The raving vegans can screech all they like about calcium loss in urine, but it doesn’t seem to have any meaningful effect on bone density. And to prove this is not a fluke publication.
Dairy foods and bone health: examination of the evidence
It is unclear whether dairy foods promote bone health in all populations and whether all dairy foods are equally beneficial. The objective of this review was to determine whether scientific evidence supports the recommendation that dairy foods be consumed daily for improved bone health in the general US population. Studies were reviewed that examined the relation of dairy foods to bone health in all age, sex, and race groups. Outcomes were classified according to the strength of the evidence by using a priori guidelines and were categorized as favorable, unfavorable, or not statistically significant. Of 57 outcomes of the effects of dairy foods on bone health, 53% were not significant, 42% were favorable, and 5% were unfavorable. Of 21 stronger-evidence studies, 57% were not significant, 29% were favorable, and 14% were unfavorable. The overall ratio of favorable to unfavorable effects in the stronger studies was 2.0 (4.0 in <30-y-olds, 1.0 in 30–50-y-olds, and 1.0 in >50-y-olds). Males and ethnic minorities were severely underrepresented. Dairy foods varied widely in their content of nutrients known to affect calcium excretion and skeletal mass. Foods such as milk and yogurt are likely to be beneficial; others, such as cottage cheese, may adversely affect bone health. Of the few stronger-evidence studies of dairy foods and bone health, most had outcomes that were not significant. However, white women <30 y old are most likely to benefit. There are too few studies in males and minority ethnic groups to determine whether dairy foods promote bone health in most of the US population.
This one has a different data set, hence the different numbers. So the next time someone waves a ‘dairy causes osteoporosis’ study at you, ask them ‘where the masses of other studies are that show the opposite?‘. I’ve found that many vegans are effectively ‘fundamentalist’ in mindset, anything that doesn’t agree with them doesn’t exist. Which in this case is the majority of dairy/BMD studies.