Calcium
The primary mineral in bone, best obtained from food first.
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What it is
Calcium is the most abundant mineral in the body and the main structural element of bone and teeth. It also supports muscle and nerve function. Dairy, fortified foods, and leafy greens are dietary sources.
How it works
Calcium is the most abundant mineral in the body, and about 99% of it is stored in bones and teeth, giving them structure. The rest is essential for muscle contraction, nerve signaling, and blood clotting. Your body keeps blood calcium in a tight range — if your diet falls short, it pulls calcium from bone to compensate, which over years can weaken the skeleton.
What it's been studied for
Used to support bone health, usually alongside vitamin D, when dietary intake falls short.
What the evidence shows
A National Osteoporosis Foundation meta-analysis found calcium plus vitamin D reduced fracture risk. The benefit is clearest when you're not already getting enough from food.
Who should consider it
Calcium matters most for people not meeting their needs from food — including those who avoid dairy, postmenopausal women (who lose bone faster), older adults, and people on long-term steroids. The goal is to reach your total daily target from food first and supplement only the gap. Adequate vitamin D is needed alongside it for absorption.
Amounts commonly studied
Aim to meet total needs (around 1,000-1,200 mg per day for most adults) from food first; supplement only the gap. Doses above ~500 mg are best absorbed split through the day.
How to take it
Aim for the total daily target (about 1,000-1,200 mg for most adults) from food plus supplements combined — not a full dose on top of a good diet. Your body absorbs calcium best in doses of 500 mg or less, so split larger amounts across the day. Citrate can be taken any time; carbonate needs food. Pair with vitamin D, and separate high-dose calcium from iron and certain medications.
Forms & absorption
Citrate absorbs well with or without food and suits people on acid-reducing medication; carbonate is cheaper but needs food. Often paired with vitamin D and magnesium.
Food sources
Dairy (milk, yogurt, cheese) is the classic source; also fortified plant milks and juices, calcium-set tofu, canned sardines and salmon (with bones), and leafy greens like kale and bok choy.
Safety & interactions
Meeting needs from food is preferable — very high supplemental calcium hasn't shown added benefit and may carry cardiovascular and kidney-stone concerns in some people. Don't overshoot.
Myths & what it won't do
Myth: more calcium means stronger bones. Reality: beyond meeting your needs, extra calcium adds no benefit, and very high supplemental doses have raised concerns about kidney stones and, in some studies, heart health. Myth: supplements are the best source. Reality: food calcium comes with other bone nutrients and appears safer — supplements are for filling a genuine gap.
Common questions
- Citrate or carbonate?
- Citrate absorbs well with or without food and suits people on acid-reducing medication; carbonate is cheaper but needs food. Both work if used correctly.
- Do I need vitamin D with it?
- Yes — vitamin D is required to absorb calcium, which is why the two are studied and sold together for bone health.
- Is too much calcium harmful?
- Very high supplemental calcium hasn't shown added bone benefit and may raise kidney-stone risk, so meeting needs mostly from food and filling only the gap is the safer approach.
The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.
Related goals
Guides that cover Calcium
Research on Calcium
Recommendations on this page are informed by published research. This is educational information, not medical advice.
- Weaver CM, Alexander DD, Boushey CJ, et al. Calcium plus vitamin D supplementation and risk of fractures: an updated meta-analysis from the National Osteoporosis Foundation. Osteoporos Int. 2016;27(1):367-376. View study →Note: Supports calcium and vitamin D taken together; more recent trials of vitamin D alone in general populations show little benefit, so the effect is clearest for the combination in older or at-risk adults.