Having problems with bone density myself, due to celiac disease, I have been a little concerned about the relationship between a high protein diet and calcium excretion.
As I understand it, the CW take on this is that if you eat more protein, you create a more acid state in your blood, which your body balanced by taking calcium from your bones. (Obviously not good if you're a bit thin in the skeletal department).
This is an eye-opener:
To summarize, the authors found that if you eat more meat, you do not cannibalize more calcium, IF:
You eat less grains! Yee-hah to that, I say! Yep, it's the grains causing all the acidity. What's more, if you eat more veggies at the same time, you improve the picture still further.
Which, for me, gives a great explanation how Grok maintained an impressive skeleton without 2 pints of milk a day plus a handful of calcium capsules. (It never made sense, I just couldn't work out why).
And, as a osteo-challenged celiac, I'm excited about my next Bone Mass Density scan. Can't wait to tell the consultant how I did it