Mineral
Calcium
Almost all of it is in your skeleton, and the skeleton stops accepting deposits somewhere in your late twenties. What you build before then is what you spend for the rest of your life.
What it does
Around 99% of the calcium in your body is structural — it is the mineral that makes bone and teeth rigid. The other 1% is doing something more urgent: every muscle contraction, every nerve signal and every step of blood clotting needs calcium ions at a very precise concentration.
That 1% is defended absolutely. If blood calcium starts to fall, parathyroid hormone rises and the body dissolves bone to restore it. This is why a blood test tells you almost nothing about calcium intake: the number stays normal right up until the skeleton has been paying for it for years.
Bone mass accumulates through childhood and adolescence, peaks somewhere between the mid-twenties and thirty, and declines slowly afterwards. The teenage years are the single largest deposit anyone makes, which is why the recommendation for a fourteen-year- old is higher than for their parents.
How much you need
| Who | Per day | Note |
|---|---|---|
| Infants, 0–6 months | 200 mg | Adequate Intake |
| Infants, 7–12 months | 260 mg | Adequate Intake |
| Children, 1–3 years | 700 mg | — |
| Children, 4–8 years | 1,000 mg | — |
| Ages 9–18 | 1,300 mg | The highest figure in the table, and not by accident |
| Adults, 19–50 | 1,000 mg | — |
| Women, 51 and over | 1,200 mg | Bone loss accelerates after menopause |
| Men, 51–70 | 1,000 mg | — |
| Adults, 71 and over | 1,200 mg | — |
More is not better. Above roughly 2,000–2,500 mg a day from food and supplements combined, the evidence for benefit disappears and the risk of kidney stones rises. Calcium is a nutrient where the useful range has a ceiling as well as a floor.
From our own data
The foods highest in calcium
Dairy dominates by amount, but not by absorption: the calcium in low-oxalate greens such as kale and bok choy is taken up at roughly twice the rate of the calcium in milk. Spinach is the famous exception — it is rich in calcium and almost none of it is available.
- 1
Poppy seeds111% · DV - 2
Sesame seeds, toasted97% · DV - 3
Parmesan, grated96% · DV - 4
Fermented tofu (fuyu), set with calcium95% · DV - 5
Wholegrain white bread, toasted58% · DV - 6
Cotija cheese54% · DV - 7
Chia seeds49% · DV - 8
Nettles, blanched37% · DV - 9
Agave, cooked35% · DV - 10
Winged beans, dry34% · DV - 11
Fireweed leaves, raw33% · DV - 12
Sardines, canned29% · DV
Per 100 g, from our copy of USDA FoodData Central, against a Daily Value of 1,300mg. Ranked by amount, not by how much of it your body actually takes up — read the next section before you act on the order.
The table above is per 100 g. The app weighs the portion you actually ate.
What helps, and what gets in the way
Helps
- Vitamin D, without which the gut absorbs a fraction of what arrives
- Splitting intake — absorption is most efficient in doses of about 500 mg or less
- Low-oxalate greens: kale, bok choy, broccoli, watercress
- Fermentation and soaking, which reduce the phytate in beans and grains
Gets in the way
- Oxalate, which is why spinach, rhubarb and beet greens give up very little of theirs
- Very high sodium intake, which increases calcium lost in urine
- Excess caffeine and alcohol, modestly
- Taking it at the same time as an iron supplement — each blocks the other
Absorption sits around 30% from most foods and falls as the dose rises, which is the argument for spreading it across meals rather than taking one large supplement. It also falls with age: an older adult absorbs materially less than a teenager from the same glass of milk, which is part of why the recommendation goes back up after seventy.
Who tends to fall short
Groups where intake or absorption is commonly lower than the reference. It is a list of populations, not a list of symptoms — it cannot tell you anything about yourself.
- Teenagers, who need the most and often drink the least milk
- Postmenopausal women, through falling oestrogen and faster bone turnover
- People avoiding dairy without replacing it with fortified or high-calcium alternatives
- People with lactose intolerance who have cut dairy rather than switched form
- Anyone on long-term corticosteroids
Cook it
Braised kale and white beans with lemon
Two, as a side; about twenty minutes
Ingredients
- 250 g kale, stems stripped, leaves torn
- 1 tin white beans, drained and rinsed
- 2 cloves garlic, sliced
- 2 tbsp olive oil
- 100 ml water or stock
- Zest and juice of half a lemon
- Black pepper
Method
- 1Strip the stemsHold the base of the stem and pull the leaf away with the other hand. The stems are edible but take three times as long to soften, and this dish is short.
- 2Soften the garlicOlive oil in a wide pan over low heat, garlic in for two minutes until fragrant and barely coloured. Browned garlic turns bitter and there is nothing here to hide it.
- 3Braise the kaleLeaves and the water in, lid on, eight to ten minutes over medium-low until the kale is tender but still green. Kale that has gone olive has lost the texture that made it worth cooking.
- 4FinishBeans in to warm through, then the lemon zest and juice off the heat. Pepper, and no salt until you have tasted it — tinned beans bring their own.
Kale is a low-oxalate green, which is the point: its calcium is absorbed at roughly twice the rate of the calcium in spinach. The lemon is not only for flavour — the acid also helps the iron in the beans.
Sources
- NIH Office of Dietary Supplements — Calcium
- Dietary Reference Intakes for Calcium and Vitamin D
- USDA FoodData Central
This page is education, not medical advice. It does not diagnose anything and it is not a substitute for a clinician who knows your history. If you think you are short of calcium, the answer is a blood test and a conversation, not a supplement bought on the strength of an article.
Every food above, and 12,601 more, with the full panel — in the app.