Back in November I did some sweat loss calculations and concluded that bone loss during cycling
wasn't because of losing calcium in sweat. Turns out I was wrong about that in this post:
https://www.bikeforums.net/21204976-post47.html
and I take it back. Bone loss is due to sweating. It has little or nothing to do with cycling being non-weight bearing, it's just the sweating. There's a good paper on it here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145631/
The good news in that paper and other similar studies is that taking calcium about 2 hours before riding attenuates the bone loss. One study used 1000mg calcium citrate and 1000mg of vitamin D3.
There's also a paper showing that supplementing 1000mg/day calcium also increases cycling performance:
https://pdfs.semanticscholar.org/9d3...2565818304.pdf
It's recommended that if one supplements with calcium to also take magnesium in a 2:1 ratio, but not at the same time, though that wasn't done in these studies.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717874/