Minerals are needed in tiny amounts, but the gap between what’s on the plate and what your body actually takes up is where the real story lives. Calk reads the food, not your blood — so treat this as a map of sources, not a diagnosis.
Schematic mineral coverage from food
Illustrative — schematic coverage, not your real intake.
Sources matter more than totals#
A mineral number on its own can mislead, because the body doesn’t absorb every form equally. Iron from meat (heme) is taken up far more readily than iron from plants (non-heme), and the same plant-based iron rises or falls with what sits beside it — vitamin C lifts it, while the tannins in tea and coffee and the phytates in whole grains hold it back (Hurrell 2010). Calcium tells a similar story: it’s absorbed best in modest doses, so it lands better spread across the day than poured into one serving (NIH 2024). Calk’s job is to surface these patterns in the foods you already log, calmly and without alarm.
A few are easy to undershoot#
Some minerals quietly fall short even when you eat with variety. Magnesium sits behind hundreds of enzyme reactions, yet typical intakes often land below the everyday range of 310–420 mg (NIH 2022). Zinc has no real store in the body, so it leans on regular intake from food (NIH 2024). And iodine and selenium work as a thyroid pair, usually arriving from different food groups. None of this is a deficiency call — a low day is weak evidence, not a verdict. It’s a nudge worth checking, one option among many, and never a substitute for a clinician.
Iron Sources#
What Calk looks at. Calk totals your iron and weighs the type, because the two forms behave differently: heme iron from meat, seafood and poultry is absorbed several times more readily than the non-heme iron in plants and fortified foods (NIH 2024). On a plant-leaning plate the same milligrams land softer, so the total often needs to run higher to deliver the same usable amount — and what shares the meal matters as much as the number (Hurrell 2010). Iron deficiency is the most common nutritional shortfall worldwide, and people who menstruate and those eating mostly plants sit at higher risk (NIH 2024).
What you could try. Pair plant iron — lentils, tofu, spinach, beans — with a hit of vitamin C from peppers, citrus or tomatoes at the same meal, which measurably lifts uptake. Some people find it helps to keep tea and coffee for between meals rather than alongside the iron-rich plate, since their polyphenols tend to blunt absorption. If meat is on the plate even occasionally, it does double duty: it carries heme iron and helps you absorb the non-heme iron around it.
Calcium Sources#
What Calk looks at. Calk tracks calcium across every source you log — dairy, fortified plant milks, leafy greens, tofu set with calcium, and canned fish eaten with the bones — against a typical adult mark near 1,000 mg a day (NIH 2024). It also watches how it arrives, because the gut absorbs calcium best in doses around 500 mg or less; a single large serving is used less efficiently than the same amount spread over the day (NIH 2024). Chronically low intake is a slow story — low calcium over decades is associated with weaker bones rather than anything you’d notice in a day.
One serving vs. two — same calcium, more absorbed
Illustrative. Spreading the same calcium across two smaller doses tends to land more of it.
What you could try. If you eat dairy, two to three servings across the day usually cover the need without thinking about it. If you don’t, lean on fortified plant milks, tofu set with calcium, sesame and tahini, almonds, and canned sardines with the bones — and spread them across meals rather than stacking them into one.
Magnesium Sources#
Magnesium runs quietly behind hundreds of enzyme reactions, yet everyday intakes often sit below the 310–420 mg range, and it’s an easy one to miss without noticing (NIH 2022). Calk reads it from the whole-food sources that carry it — nuts, seeds, whole grains, beans and dark leafy greens. A small handful of pumpkin seeds covers a meaningful share of a day; almonds, spinach, black beans and even dark chocolate quietly add up alongside.
Zinc Sources#
What Calk looks at. Calk checks zinc across meat, shellfish, legumes, seeds and dairy. Two things make it worth a look: the body keeps no dedicated zinc store, so it relies on a steady supply from food, and — as with iron — plant zinc is less available because phytates bind it, so mostly-plant eaters may need meaningfully more to land the same amount (NIH 2024).
What you could try. Oysters are the richest source by a wide margin, but the everyday workhorses are beef, pumpkin seeds, chickpeas, lentils and yogurt. On a plant-leaning plate, soaking or sprouting legumes and grains, or leaning on fermented and leavened forms, frees up more of the zinc that’s already there.
Iodine & Selenium#
What Calk looks at. These two work as a thyroid pair: iodine is the raw material your body builds thyroid hormone from, and selenium powers the enzymes that switch the stored form (T4) into the active one (T3) (NIH 2024, NIH 2024). They tend to arrive from different foods, so Calk checks for both rather than assuming one stands in for the other.
What you could try. For iodine, iodized salt, dairy and the occasional bit of seaweed are the reliable anchors; for selenium, a Brazil nut or two a day is plenty, with fish, eggs and sunflower seeds backing it up. A note of caution on Brazil nuts — they’re so concentrated in selenium that a small handful daily can easily overshoot, so a single nut goes a long way and tends to be plenty rather than a full serving.