Interestingly, I have been thinking about the same question, from another perspective.
For quite some time (independently of any fasting ), I’ve been taking vitamin C, vitamin D3, vitamin K2,magnesium, zinc & selenium, for general, and some specific health benefits.
I also take Lugol’s solution (iodine dissolved in potassium iodide), so I get some potassium from that.
And I get plenty of sea salt, so sodium isn’t a problem.
Now, I’ve never taken a calcium supplement (except when I went through a phase of grinding up eggshells and dissolving them in lemon juice), but I stopped doing that ages ago.
If you’ve heard of Dr Thomas Levy, he’s 100% against calcium supplements, and has written a whole book condemning them. He reckons most people already get far too much calcium in their diet. This always sounds like a pretty big assumption to me. How does he know? If you don’t consume any milk (which people tend not to while fasting or on VLC), or cream (which I personally don’t consume while fasting or on VLC), or cheese or yoghurt (which I certainly don’t consume while fasting), then where is all this calcium coming from?
True, if you live in a hard water area, you’d be getting calcium carbonate in your water, but personally, I try to drink mostly mineral water, and I doubt if I’d be getting very much calcium out of it.
True also, that you might be getting it from bone broth, but I’ve read that you don’t actually get much. And personally, I discontinued bone broth after the 2nd week of fasting (although I might resume it occasionally later).
But the different perspective I mentioned was by reading “The Miraculous Results of Vitamin D3” by Jeff Bowles, which I have mentioned in another thread. In short, JB recommends higher than normally recommended doses of D3 together with (most important) sufficient doses of K2. (he recommends 1 capsule of LEF “Super K” for each 10,000 IU of D3; this is 1000 mcg of vitamin K2 MK-4).
Let’s not get into whether high doses of D3 are good or bad here. What’s important is that nowadays vitamin D experts agree that if you take significant doses of D3, you must also take K2, as it helps to make sure your calcium goes into or stays in your bones, where it belongs, and not in your soft tissue, where it doesn’t.
But interestingly he talks about some users of K2 having too low blood levels of calcium, because the K2 has put it all into their bones; too much of a good thing. How do you know if you are taking too much K2? I’m not sure, and I can’t find the right place in the book just now. He recommends that if people have problems, they back off the K2 a little.
My thought was: why not add a calcium supplement?
I looked for what might be a good one, and found it was possible to get calcium ascorbate in powder form, quite cheaply, and ordered some; it happened to arrive today.
Since I like to take vitamin C anyway, the ascorbate form is perfect. The Ca and the ascorbate ions should disassociate, and go off separately and do their own good things.
I’m going to look up what is supposed to be the correct daily intake of calcium, then look on the Calcium ascorbate packet to work out how much of that I need to take to get the “official” dose of calcium, and work from there.
Sorry, that probably doesn’t really answer your question, but I thought you might be interested.