Single Calcium Citrate has the absorption rate of almost 60-70%. Calcitriol or the active form of vitamin D3 is added to any calcium supplement to increase the absorption of calcium. So, in the case of Ca-citrate+Calcitriol combination what will be the absorption rate?
Giving calcitriol should only be done under special circumstances. Define those first, as one would never add calcitriol to a calcium supplement only to improve calcium absorption in an otherwise healthy person. There is a misconception that one must add the "active" form of vitamin D and bypass vitamin D itself, but vitamin D works just fine being converted to 25-OHD and then to 1,25. All of this is done in a safe and controlled way.
Though in few cases it matters what amount calcitriol is added and what the outcome of that combination is.
Combining calcitriol and a calcium supplement needs to be conducted in very special cases. BEC Nordin published data that calcium carbonate (1 gm) with 250 nanogms of calcitriol reduced bone resorption in postmenopausal women with malabsorption of calcium. For these patients 1 gm calcium carbonate was ineffective to modulate bone resorption. Calcium citrate (500 mgms) generates approximately the same level of inhibition of bone resorption as 1 gm calcium carbonate. These data are available in the literature.
I doubt that in humans many indications exist where calcium citrate should be given in combination with cacltriol. In almost all circumstances it seems to be preferable to offer either vitamin D or calcidiol together with calcium. In general, renal calcitriol prduction is closely regulated by the calcium homeostatic system (i.e. concentration of ionized calcium in blood, the Ca (++) X Pi product, the concentration parathyroid hormone, sex hormones ect.). When calcitriol is added, the protective function of this homeostatic calcium control system is circumvented. This requires careful medical control in order to avoid hypercalcaemia.
The absorption rate of the calcium ion from calcium citrate depends among other factors on the age of the individual (e.g.growing or adult), on the reproductive state (e.g. non-pregnant, pregnant, lactating) on the acidity of the diet (acid/base balance) and last not least on the hormonal status of the individual (e.g. parathyroid function, postmenopausal period etc.). Depending on these conditions intestinal calcium absorption rates may vary from 2 to 30 % of the administered oral dose.
Dear Johein Harmeyer,
so what do your prefer in case of using it as supplementation or not?
The information by Johein Harmeyer is consistent with my information. I personally prefer to suggest exposition of skin to sun. One day full exposition promotes absorption for 20 days.
Skin tumors develop sfter skin burnings, mainly in children or young adults
For an adult, living in the northern hemisphere with normal sun exposure, I would prefer a vitamin D3 supplement of about 1000 iU/d during the winter season. If such a person is consuming a reasonable amout of milk products e.g. milk or yoghurt or cottage cheese ect.,he will probably need no extra Ca-supplement. In case he needs extra calcium by some unkowns reasons, it makes probably not much of a difference what sort of formulation is chosen as a calcium supplement. Calcium salts are reasonably soluble and calcium is being absorbed as an free calcium ion. The concentration of the calcium ions in the intestinal digesta is determined by the pH and by the presence of many other anions which are simultanously present in the intestinal content and which will all interact with each other. In the gut the citrate ion may be far away from the calcium ion when it is being absorbed at the brush border.
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