Calcium only helps if it reaches bone

Vitamin D's active form is the principal hormonal regulator of calcium absorption in the intestine. It drives the transport machinery that moves calcium from the gut into the bloodstream. Without enough of it, much of the calcium you swallow is not absorbed.

This is a high dose. The Recommended Dietary Allowance for adults is 600 IU a day, rising to 800 IU after age 70, and the Institute of Medicine set a Tolerable Upper Intake Level of 4,000 IU a day for adults. At 5,000 IU, one Truina capsule is above that upper level. Many clinicians do prescribe doses in this range, particularly for people with low vitamin D status — but that is a decision to make with your own clinician, especially if you already take a vitamin D supplement or a multivitamin containing one. Please check before adding this.

Vitamin K is the cofactor that carboxylates osteocalcin and matrix Gla protein — the step that switches those proteins into their calcium-binding form. Osteocalcin is made by bone-building cells and is involved in bone mineralisation.

We should be straightforward about the trials. A 3-year study in 244 healthy postmenopausal women found that 180 mcg of MK-7 daily slowed the age-related decline in bone mineral density. A later 3-year study in 142 postmenopausal women with osteopenia used 375 mcg daily, on top of calcium and vitamin D, and found no effect on bone mineral density, bone microarchitecture, or turnover markers — even though carboxylation improved. So the evidence is genuinely mixed, and our 100 mcg is below the dose used in the trial that found a benefit. We include K2 because the mechanism is well established and the safety profile is good, not because the outcome data are settled.

In a double-blind study, 5 mg of piperine taken alongside coenzyme Q10 produced roughly 30% higher plasma levels of CoQ10 than CoQ10 alone. Piperine has also been shown to increase serum response to beta-carotene.

Two honest caveats. First, that research tested piperine with coenzyme Q10 and beta-carotene — not with vitamin D3 or K2. We are reasoning from the same fat-soluble absorption pathway, which is a reasonable inference, not a demonstrated result for these specific nutrients. Second, the authors of the coenzyme Q10 study were affiliated with the company that manufactures BioPerine®. We think the finding is still worth citing; you should know who ran it.

Calcium is the primary mineral in bone tissue, and adequate intake supports the maintenance of normal bones.

210 mg is a fraction of a full day's calcium requirement, and that is deliberate. Truina tops up a diet that already contains calcium; it does not replace it. High-dose calcium carbonate is also a common cause of constipation, which matters more when digestion is already slowed. And carbonate depends on stomach acid, which is why the directions say to take it with your largest meal rather than whenever you remember.