?? Why not? the two are very often combined (not that that in itself means it's good) and my chiro and my natural health practitioner both recommended that I take both with no mention of not taking them at the same time. In this case it is calcium citrate and magnesium glycinate.
No supplementing calcium?
This is probably a matter of conventional thinking (to supplement it) vs. (some) functional thinking that magnesium (and vitamin D) are far more important.
I've had another look why exactly, and same as the first time I at least for myself am fairly convinced
not to take calcium, that what I get via veggies is enough, and specifically for fibro that it is only magnesium I (we?) need.
The main problem seems to me to be that quite a few people say that most of us already get enough, praps too much, calcium from our normal diets, which are geared to that (e.g. calcium-fortified or dairy), whilst we don't get enough magnesium from our normal diets.
Specifically for fibro: Too low magnesium and high calcium leads to our sleep problems (too high cortisol), muscle problems (calcium is for tension, magnesium is for relaxation) and constipation.
Stress lowers magnesium, which increases cortisol, which again causes stress.
It is correct that calcium and magnesium need to be in a certain balance to one another, 2:1, but if the calcium is already in the diet then it doesn't need to be supplemented as much as magnesium.
Both are good for brain, bones, sleep, muscles, gut, skin, heart, joints, but in different, often opposite complementary ways.
At high doses they can interfere with one another, in lower doses probably not much.
Excess calcium can praps cause cardiovascular issues (inconsistent evidence), but this may be due to
low magnesium causing lower absorption calcium in the bones etc. so that it creates problems in our blood.
Calcium should if at all be supplemented less than 500mg elemental and <1000mg gross calcium, some say 400 max. in diet, less the older you get. The US and German recommendations are higher.
Getting calcium via diet is better due to it being spread over the day. To uptake calcium better vitamin D is necessary, esp. with K2 in the MK7 form.
An aside: As opposed to calcium carbonate, calcium citrate can be taken without food. But calcium is normally best with food.
These are examples of sources seem to be mainly functional/neuropathic and contradicting established views.
1) hcfricke (German) referencing Dr. Thomas E. Levy "Death By Calcium", which is probably exaggerating it.
2) drnewtons connection-calcium-magnesium
3) globalhealing calcium-and-magnesium