Yes. A membrane does not sort what it rejects into wanted and unwanted; it separates by size and charge, so calcium and magnesium leave with everything else dissolved. That is the honest answer, and the useful part of the discussion starts after it.
How much of your intake was in the water
For most people on a normal diet, the great majority of mineral intake comes from food rather than from tap water. That is why national health guidance is written around diet. It is also why the answer is different for someone who drinks several litres a day of a particular mineral-rich supply — the general case and the individual case are not the same case.
Taste is the real complaint
Water with very little dissolved in it tastes flat to many people. This is a preference, not a health finding, and it is what remineralisation stages are actually selling: a small, controlled addition after the membrane to put body back into the water. A post-carbon stage does something adjacent — it finishes taste rather than restoring minerals.
What to ask before buying a remineralising stage
- What does it add, and roughly how much?
- How often is that stage replaced, and at what cost?
- Does it change the system's rated output or its pressure requirement?
Whether a given KomiBright model offers a post-carbon or mineral stage is a per-model question — the KB-C25RP, for one, is the C25R platform with a post-carbon option — and belongs on the model's own page rather than in a general article.
