Calcium: Benefits and sources

Calcium: Benefits and sources
Woman washing broccoli in the kitchen sink

Calcium is a nutrient required by all living organisms including humans. It is the body’s most abundant mineral and vitally essential for bone health.

People need calcium to build and sustain strong bones, and 99 percent of calcium in the bones and teeth is in the blood. The preservation of healthy contact between the brain and other parts of the body is also important. It plays a part in cardiovascular and muscle movement.

Calcium occurs naturally in many foods, and is added to other items by food manufacturers. Supplements are available too.

People do need vitamin D alongside calcium, as this vitamin allows the body to absorb calcium. Vitamin D originates from fish oil, fortified dairy products and sunlight exposure.

This article explores why the body needs calcium, the foods are high in calcium, what happens if the body doesn’t have enough, and what the pros and cons of taking supplements are.

Why we need calcium

broccoli un the pot
Green leafy vegetables, such as broccoli, are a good source of calcium.

Calcium plays various roles in the body. These include the following:

Bone health

In the human body, about 99 per cent of calcium is in the bones and teeth. Calcium is indispensable for bone production, growth, and maintenance.

As the children grow, calcium allows their bones to develop. Calcium helps to help stabilize the bones and slow down the loss of bone density which is a normal part of the aging process when a person stops developing.

Females who have had menopause already can lose bone density at a higher rate than males or younger people. They are more likely to develop osteoporosis, and a doctor can prescribe calcium supplements.

Muscle contraction

Calcium helps to control contracting muscles. As a nerve activates a muscle, calcium is released into the body. The calcium helps the muscle proteins conduct contraction work.

As the calcium is drained out of the muscle by the body the muscle can relax.

Cardiovascular system

Calcium plays a vital function in clotting the blood. The clotting mechanism is complex, and it has many phases. These contain a number of chemical substances like calcium.

The role of calcium in muscle function involves the maintenance of heart muscle activity. Calcium loosens the smooth tissue covering the blood vessels. Various research suggested a potential link between high calcium intake and lower blood pressure.

Vitamin D is also important to bone health, and helps to absorb calcium in the body. Find out more on and why we need vitamin D.

Other roles

Calcium is a co-factor of a variety of enzymes. Some primary enzymes can’t function efficiently without calcium.

Studies have also indicated that adequate calcium intake will lead to:

  • a lower risk of developing conditions involving high blood pressure during pregnancy
  • lower blood pressure in young people
  • lower blood pressure in those whose mothers who consumed enough calcium during pregnancy
  • improved cholesterol values
  • a lower risk of colorectal adenomas, a type of non-cancerous tumor

Calcium-rich foods

People can obtain calcium from a range of foods and drinks.

The following are good sources:

  • yogurt
  • milk
  • fortified dairy alternatives, such as soy milk
  • sardines and salmon
  • cheese
  • tofu
  • green leafy vegetables, such as broccoli, turnip leaves, watercress, and kale
  • many fortified breakfast cereals
  • fortified fruit juices
  • nuts and seeds, especially almonds, sesame, and chia
  • legumes and grains
  • cornmeal and corn tortillas

Some dark green vegetables, including spinach, have calcium in it. They contain even high levels of oxalic acid, however. According to research, oxalic acid reduces the body’s ability to consume calcium.

How much do I need?

According to the Office of Dietary Supplements (ODS), people need the following amounts of calcium:

  • 0–6 months: 200 milligrams (mg)
  • 7–12 months: 260 mg
  • 1–3 years: 700 mg
  • 4–8 years: 1,000 mg
  • 9–18 years: 1,300 mg
  • 19–50 years: 1,000 mg
  • 51–70 years: 1,000 mg for males and 1,200 mg for females
  • 71 years and above: 1,200 mg

Pregnant and breastfeeding women require 1,000–1,300 mg depending on age.

A doctor may recommend additional calcium for people who:

  • have started menopause
  • stop menstruating due to anorexia nervosa or excessive exercise
  • have lactose intolerance or a cow’s milk allergy
  • follow a vegan diet

Calcium deficiency

The following conditions or lifestyle behaviors may lead to low levels of calcium also known as hypokalemia:

  • bulimia, anorexia, and some other eating disorders.
  • mercury exposure
  • overconsumption of magnesium
  • long-term use of laxatives
  • prolonged use of some medicines, such as chemotherapy or corticosteroids
  • chelation therapy used for metal exposure
  • lack of parathyroid hormone
  • people who eat a lot of protein or sodium may excrete calcium.
  • some cancers
  • high consumption of caffeine, soda, or alcohol
  • some conditions, such as celiac disease, inflammatory bowel disease, Crohn’s disease, and some other digestive diseases
  • some surgical procedures, including removing the stomach
  • kidney failure
  • pancreatitis
  • vitamin D deficiency
  • phosphate deficiency

Calcium is absorbed by the body in sweat, urine, and feces. Foods and activities which promote these functions may reduce calcium levels in the body.

Calcium supplements

For people who have a calcium deficiency, a doctor may prescribe calcium supplements.

Individuals using calcium supplements should:

  • check first with their doctor whether they need supplements
  • follow the dosage the doctor recommends
  • take the supplement with food for best absorption and to minimize possible adverse effects
  • consume the supplements at intervals, usually two or three times a day

Around 43 percent of all adults in the US take calcium supplements, including 70 percent of older females, according to the ODS. On average, taking supplements will increase the daily calcium intake by about 300 mg of calcium a day.

There are also several calcium supplements which contain vitamin D. Vitamin D stimulates protein synthesis in the body, and helps to digest calcium in the body. Magnesium also plays a part in strengthening the bones, and can also include magnesium in calcium supplements.

Types of supplement

Supplements are of different types. A doctor may prescribe the optimum alternative. This will depend on the needs and desires of the patient, any medical problems that they have and whether they are taking any medicines.

Elemental calcium is the only mineral but with other substances, calcium occurs in its natural form.

Supplements that contain varying proportions of calcium compounds and calcium elementals. For instance:

Calcium carbonate: This contains an elemental calcium of 40 per cent. This type is widely available, and fairly inexpensive and convenient. A individual should take it with food, as it helps the body absorb stomach acid.

Calcium lactate: This contains an elemental calcium of 13 percent.

Calcium gluconate: contains an elemental calcium of 9 percent.

Calcium citrate: It contains an elemental calcium of 21 per cent. A person can take it with or without food. It is useful for people with inflammatory bowel disease, achlorhydria, and some absorption disorders.

Risks of supplements

Analysis has found contradictory data about the benefits and drawbacks of using supplements.

Most experts believe that it is easier to get nutrients from natural food sources, although this can often not get enough.

However, some reports have indicated that the introduction of calcium may be harmful.

Side effects

Some people experience gastrointestinal symptoms when using calcium supplements, such as bloating, constipation, gas or a combination of all three.

Calcium citrate usually has fewer and less pronounced side effects relative to calcium carbonate. Taking the food supplements or spreading their consumption across the day can help to minimize side effects incidence or severity.


Very high levels of calcium can lead to:

  • kidney problems
  • calcification of soft tissues and blood vessels
  • kidney stones
  • constipation

While high levels of calcium due to taking too many supplements can cause these serious side effects, according to the ODS, they are more likely the result of cancer and thyroid problems.

Possible complications

Past studies have raised concerns that taking calcium supplements may increase the risk of:

  • kidney stones
  • a reduction in iron absorption
  • a higher risk of a heart attack

Newer research, however, have shown that those fears might be unfounded.

Calcium may interfere with other medications. Experts offer advice as follows:

  • Take calcium supplements separately from some antibiotics.
  • Avoid supplement use while taking calcium channel blockers, which are a common type of medication for lowering blood pressure.


Calcium is important for the development and maintenance of healthy bones and teeth. It can also help to control the blood pressure, among other functions.

Adequate calcium is best obtained from dietary sources, such as dairy products, green leafy vegetables and tofu. And for some people, a doctor might prescribe supplementation.

Experts do not recommend calcium supplementation for all, due to individual requirement variations. Anyone who is considering taking supplements should get advice from their health care provider.


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