Calcium
Calcium is the body's most abundant mineral. Most is stored in bones and teeth, while a smaller circulating pool supports muscle function, nerve transmission, blood clotting and cell signalling.
What it does in the body
- Builds and maintains bone and teeth structure
- Supports normal muscle contraction
- Participates in nerve transmission and blood clotting
- Involved in cell signalling and hormone secretion
Daily reference intake
In the U.S. DRI system, most adults 19–50 need 1,000 mg/day. Women 51–70 and adults over 70 generally need 1,200 mg/day.
What can deficiency look like?
- Chronically low intake can contribute to reduced bone mineral density
- Severe low blood calcium can cause muscle spasms or tingling but usually reflects medical causes rather than diet alone
Who may be at higher risk?
- People who avoid dairy without suitable alternatives
- Postmenopausal women
- People with certain malabsorption disorders
- People with long-term very low calcium intake
Food sources
A varied diet is the first place to look for nutrients. Availability and nutrient content can vary by food, preparation and country.
Food-source note: Calcium absorption varies by food. Oxalates in some greens can reduce absorption, while fortified foods can be important alternatives to dairy.
Absorption & practical context
Active calcium absorption is regulated partly by vitamin D. Fractional absorption is generally higher at lower doses, so large supplemental doses are often divided.
Important interactions
- Calcium can reduce absorption of levothyroxine and some antibiotics when taken together
- High supplemental calcium can interfere with iron absorption in some situations
Safety and context
The adult UL is 2,500 mg/day for ages 19–50 and 2,000 mg/day for older adults in the U.S. DRI system. Excess supplement intake can cause gastrointestinal effects and may raise kidney-stone risk in susceptible people.
Scientific sources
NIH Office of Dietary Supplements — Calcium ↗ EU Register of Nutrition and Health Claims ↗Products whose current label lists this nutrient
The entries below are based on current manufacturer label information for the selected market. Compare the stated amount per daily serving and read the official product page before purchasing.