What is calcium?
Calcium is a mineral and electrolyte that the body cannot
make; it must come from food or supplements. Around 99% of body calcium is
stored in bones and teeth as hydroxyapatite, giving them strength and acting as
a reservoir to keep blood calcium stable.
Main functions in daily life
- Structural:
Builds and maintains strong bones and teeth throughout life.
- Muscle
action: Allows muscles (including the heart) to contract and relax.
- Nerve
signaling: Helps nerves send messages between brain and body.
- Blood
clotting: Essential for normal clot formation when you bleed.
- Hormone
and enzyme activity: Acts as a messenger for many hormones and enzymes in
cells.
Because calcium is needed every second, the body tightly
controls blood levels; when intake is low, it pulls calcium out of bones to
keep blood calcium normal.
Who needs calcium most, and why?
Everyone needs calcium, but some groups are at higher risk
if intake is low:
- Children
and teenagers: Rapid bone growth and peak bone mass building years.
- Pregnant
and breastfeeding women: Extra demand for baby’s bone development.
- Women
after menopause: Falling estrogen speeds bone loss, raising osteoporosis
risk.
- Older
adults (men and women): Absorption falls with age; bone density declines.
- People
with vitamin D deficiency, gut disease, or on certain medicines: Absorb
less calcium and may develop hypocalcemia and weak bones.
Average recommended intake for most adults is about 1,000
mg/day; it increases to about 1,200 mg/day for women 50+ and men 71+.
Where is calcium found in food?
Dairy is famous for calcium, but many non‑dairy foods also
provide it.
Dairy sources (approximate mg per serving):
- Milk
(any type), 8 oz: about 300 mg
- Plain
low‑fat yogurt, 6 oz: about 310 mg
- Cheddar
cheese, 1 oz: about 205 mg
- Part‑skim
ricotta, 4 oz: about 335 mg
Non‑dairy animal sources:
- Sardines
with bones, 3 oz: about 325 mg
- Canned
salmon with bones, 3 oz: about 180 mg
Plant and vegetable sources:
- Collard
greens, cooked 1 cup: about 266 mg
- Kale,
cooked 1 cup: about 179 mg
- Soybeans
(edamame), cooked 1 cup: about 175 mg
- Bok
choy, cooked 1 cup: about 160 mg
- Broccoli,
cooked 1 cup: about 60 mg
- Dried
figs, 2 pieces: about 65 mg
- Orange,
1 medium: about 55 mg
Fortified foods and others:
- Fortified
soy/almond/rice milk, 8 oz: about 300–450 mg
- Fortified
orange juice, 8 oz: about 300 mg
- Tofu
made with calcium salts, 4 oz: about 205 mg
- Fortified
breakfast cereals, oatmeal, and breads: 100–200 mg per serving (check
label)
These values are approximate and vary by brand and
preparation, so nutrition labels give the most accurate figures.
Calcium content of some common foods is illustrated in this
bar chart.
Calcium content of common foods per typical serving.
How calcium is absorbed and regulated
Calcium absorption happens mainly in the small intestine and
depends heavily on vitamin D.
- Vitamin
D (as active 1,25‑dihydroxyvitamin D3) increases production of calcium
transport proteins in intestinal cells, boosting active absorption.
- Some
calcium also moves passively between cells; this works better when intake
is higher.
- The
parathyroid hormone (PTH) and calcitonin hormones keep blood calcium in a
narrow range.
- Low
blood calcium → PTH rises → kidneys save calcium, make more active
vitamin D, and bones release stored calcium.
- High
blood calcium → calcitonin helps move calcium into bone and increases its
loss in urine and reduces gut absorption.
Calcium is a vital mineral that builds bones and teeth, supports muscles and nerves, and helps blood clot properly. Without enough calcium (and vitamin D), bones become weak and the risk of fractures and osteoporosis rises, especially with age.
Calcium absorption and what reduces it
If vitamin D is low, even a calcium‑rich diet will not be
fully absorbed, so both nutrients must be adequate. Several factors influence
absorption:
- Helps
absorption:
- Sufficient
vitamin D from sunlight, food, or supplements.
- Eating
calcium in smaller doses (≤500 mg) several times per day rather than a
single very large dose.
- Slightly
acidic stomach environment (normal digestion).
- Reduces
absorption or increases loss:
- Very
high sodium (লবণ)
intake increases calcium loss in urine.
- Excess
caffeine and soft drinks may slightly increase urinary calcium loss.
- Large
amounts of oxalates (in spinach, beet greens) or phytates (in unsoaked
bran) can bind calcium and reduce absorption from that meal.
- Some
gut conditions (celiac disease, inflammatory bowel disease, bariatric
surgery) and some medicines (certain anticonvulsants, steroids, PPIs)
impair absorption or accelerate bone loss.
Because of these interactions, NewsWebFit often recommends
focusing first on food sources, vitamin D status, and overall diet quality
before jumping to high‑dose supplements.
How much calcium is “too much”?
While deficiency damages bones, chronic excessive intake
(especially from supplements) can also be harmful.
- Many
experts suggest staying below about 2,000–2,500 mg/day total calcium from
food + supplements for adults unless a specialist advises otherwise.
- Very
high supplemental doses have been linked in some studies to kidney stones
and possibly cardiovascular issues, though data are mixed.
The general principle from NewsWebFit:
Get most of your calcium from food, use supplements only to cover the gap, and
stay within recommended daily totals.
Who should pay special attention to calcium?
- Women
after 50 and men after 70: Highest risk for osteoporosis; adequate
calcium plus vitamin D and exercise are critical.
- People
with family history of osteoporosis or fragility fractures.
- People
with lactose intolerance or dairy allergy: Need planned non‑dairy and
fortified sources, or guided supplementation.
- Those
on long‑term steroids or certain other medicines: These can
accelerate bone loss, so bone‑protective nutrition is essential.
Regular bone‑density testing (DEXA scan) is often advised in
these groups, depending on age and risk factors.
How calcium, vitamin D, and lifestyle work together
Calcium alone is not enough; bone health is a whole‑body
project.
- Calcium provides
the raw material for bones and teeth.
- Vitamin
D ensures calcium is absorbed efficiently and helps place it in bone.
- Protein supports
the bone matrix but should be balanced with enough calcium.
- Exercise—especially
weight‑bearing (walking, jogging) and resistance training—signals bones to
stay dense and strong.
- Avoiding
smoking and limiting alcohol reduces bone loss and fracture risk.
NewsWebFit emphasizes this “nutrient + hormone + lifestyle”
triangle whenever discussing calcium and bone protection.
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Visual: Calcium in common foods
The chart below shows approximate calcium content per usual
serving of several foods, including dairy and non‑dairy options.
Calcium content of common foods per typical serving
These values highlight that people who do not drink milk can
still reach daily targets using greens, fortified plant milks, tofu, canned
fish with bones, and yogurt or cheese if tolerated.
Conclusion
Calcium is much more than a “bone mineral”—it is a 24‑hour
worker in muscles, nerves, blood clotting, and cell signaling. NewsWebFit
stresses that lifelong, steady intake of calcium‑rich foods, adequate vitamin
D, and an active lifestyle are the safest way to protect bones and overall
health. Children, teens, post‑menopausal women, older adults, and people with
digestive or hormonal issues need to be especially careful, as unrecognized
calcium and vitamin D shortages silently weaken bones for years before fractures
appear.
Anyone considering supplements, or worried about bone pain,
frequent fractures, kidney stones, or abnormal calcium blood tests, should
consult a qualified healthcare professional for personalized testing and advice
rather than self‑treating.
Disclaimer
This NewsWebFit article is for educational purposes only and
does not replace professional medical advice, diagnosis, or treatment. Always
consult your doctor or a registered dietitian before changing medicines,
starting supplements, or making major diet or lifestyle changes, especially if
you have kidney disease, heart disease, hormonal problems, or are pregnant or
breastfeeding.
Article sources
- StatPearls:
Physiology, Calcium.
- Merck
Manuals: Overview of Calcium’s Role in the Body.
- MyHealthfinder
(US HHS): Get Enough Calcium; Calcium Shopping List.
- National
Osteoporosis Foundation: Guide to Calcium‑Rich Foods.
- “Calcium
and Vitamin D: Skeletal and Extraskeletal Health.”
- Review:
Vitamin D and Intestinal Calcium Absorption.
- Hypocalcemia
overview and complications.
- Research
on hypocalcemia as a risk factor for osteoporosis.
- Clinical
guidance on calcium supplements and safe upper limits.