Didn't watch the video! Can imagine what happened though.
Actually calcium has not been found to strengthen bones. It is vitamin D3, and vitamin K2 that work with calcium and other minerals to do this.
A meta-analysis/ study article about that:
"Milk and calcium good for the bones? Don’t think so"
I decided to revisit some of the science in this area recently. I found a quite-recent meta-analysis (amassing of similar studies) which looked at the relationship between milk consumption and risk of hip fracture . I think fracture risk, by the way, is a much better judge of the value of dairy products than bone density. The whole point, supposedly, of having dense bones is to prevent fracture, so it makes sense to look at this (not density).
Neither in women nor men was there any relationship between milk drinking and risk of fracture (higher milk consumption was not associated with reduced risk of hip fracture).
In another meta-analysis, this same group of researchers looked at the relationship between calcium intake and hip fracture . The results were the same – no reduced risk of fracture associated with higher calcium intakes.
This second meta-analysis also looked at intervention studies, in which individuals were treated with calcium. These sorts of study trump the epidemiological studies discussed so far, in that they can actually prove ‘causality’ i.e. that, say, calcium causes few fractures.
Looking at four trials in which risk of hip fracture specifically was assessed, those taking calcium (compared to placebo) turned out to be at 64 per cent increased risk of fracture. Oh. Maybe all this milk and calcium is not such a good idea after all.
1. Bischoff-Ferrari HA, et al. Milk intake and risk of hip fracture in men and women: A meta-analysis of prospective cohort studies. J Bone Miner Res. 2010 Oct 14. [Epub ahead of print]
2. Bischoff-Ferrari HA, et al. Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials. Am J Clin Nutr. 2007;86(6):1780-90.