Calcium: benefits, side effects, dosage and interactions


Calcium is the most abundant mineral in the body. 99% of the body's calcium is stored in bones and teeth, where it supports their structure and function. We get calcium from foods such as dairy products, green leafy vegetables, and fortified foods (such as non-dairy milk , juices, and cereals ).

We can also find calcium in certain medications, such as antacids, as well as in supplements . However, it is best to get your daily calcium intake from naturally calcium-rich foods whenever possible.

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Health benefits

Calcium is an essential mineral that helps your body:

  • helps in the formation of bones and teeth
  • helps maintain strength.
  • plays a role in muscle movement.
  • helps nerves carry messages between the brain and other parts of the body.
  • helps blood vessels relax and narrow (which moves blood throughout the body).
  • releasing hormones and enzymes that help carry out various bodily functions.

Bone density (calcium deposit) increases during the first 25-30 years of life and then gradually decreases with age. Adequate calcium intake is necessary to maximize maximum bone mass and limit bone loss later in life (which can lead to fractures and osteoporosis ). During periods of growth, such as adolescence, the need for calcium increases.

Particularly in postmenopausal women, bone breakdown exceeds bone formation, leading to bone loss and increasing the risk of osteoporosis over time. This is another time when you should increase your body's calcium intake .

Bone density and osteoporosis

Getting enough calcium is important for bone building and can prevent or delay bone loss later in life. This is especially important for some people who are at higher risk for bone loss.

Increased risk of bone loss

  • Postmenopausal women
  • Older

Osteoporosis, a disease characterized by porous and brittle bones, is associated with a large number of fractures. There have been many studies on calcium supplementation and osteoporosis. While some research suggests that supplements can improve certain fractures, others cannot.

The result is highly dependent on the population studied, age, and supplementation regimen. Therefore, it is always important to discuss nutritional supplements with your healthcare professional before using them.

One thing is for sure: Adequate calcium and vitamin D intake as part of a complete and balanced diet, combined with resistance exercise, can reduce the risk of osteoporosis later in life.

Colon cancer

While this is not definitive, there is ample evidence to suggest that calcium may have a preventive effect on colon cancer. For example, one review evaluated the effect of calcium supplementation on the development of colon cancer and adenomatous polyps (neoplasms that are potential precursors to cancer).

The researchers found that while the supplements may help moderate protection against adenomatous polyps, there is insufficient data to make recommendations for colon cancer prevention.

On the other hand, data from a Harvard study suggest a 35 percent reduction in distal colon cancer with increasing the dose of calcium (1250 mg of calcium per day). It appears that the amount of calcium, as well as the population that ingests it, determines how much protection calcium can provide for colon health.

Keep in mind that since there are many other factors that can increase your risk of colon cancer (genetics, weight, diet, smoking), calcium supplements alone are highly unlikely to be the answer.

If taking calcium supplements does not pose a risk to you, it may be worth discussing their potential preventive effects with your healthcare provider.

Weight control

The effect of calcium on weight control is also somewhat variable. Several studies have shown a link between higher calcium intake and lower body weight. Some studies even show that a diet rich in calcium and low in fat (when total calories are limited) can reduce the risk of obesity and accelerate weight loss in obese people.

A study published in the American Journal of Clinical Nutrition suggests that calcium has no weight-control effect unless calories are restricted. Furthermore, oral calcium intake (as opposed to dietary calcium intake) does not appear to provide such results.

If you want to lose weight , the most important thing is to make sure that you are creating some kind of caloric deficit, either through more exercise or less food. In addition, the diet should always be well balanced: rich in non-starchy vegetables, fruits, whole grains, lean proteins and healthy fats.

If you plan to add more dairy to your diet, keep in mind that whole dairy can be high in calories and saturated fat. Adding more dairy without cutting calories can lead to weight gain.


Preeclampsia is a condition that occurs in pregnant women and is characterized by high blood pressure , swelling of the hands and feet, and protein in the urine. The potential benefits of calcium in preventing pre-eclampsia have been investigated in several randomized, placebo-controlled trials.

A recent meta-analysis of 13 studies found that calcium supplementation at a dose of at least 1000 mg per day, beginning at approximately 20 weeks' gestation, was associated with a significant reduction in the risk of high blood pressure, pre-eclampsia, and preterm birth .


The verdict on whether calcium reduces blood pressure or the risk of hypertension is controversial. Some clinical trials have found a relationship between calcium intake and the risk of hypertension, while others have found no relationship. Small changes in systolic blood pressure have been observed, but the type of effect may depend on the population studied.

The effects differ between people with high blood pressure and people with normal blood pressure.

Heart disease

Research on calcium and heart disease is complex. While there appears to be no direct link between the calcium you consume from your diet and the amount in your arteries (a sign of early heart disease), recent studies have found a link between the use of calcium supplements and cardiovascular disease (CVD). ).

One theory is that the extra calcium has a stronger effect on circulating calcium levels, which can increase calcification, a marker of cardiovascular disease. Hypercalcemia is associated with increased blood clotting, vascular calcification, and arterial stiffness, which increases the risk of cardiovascular disease .

The researchers found that calcium supplements with or without vitamin D did not significantly increase the risk of cardiovascular events, especially myocardial infarction. However , again, mixed results can be found based on the study variables. Skeptics, however, argue that the available evidence linking calcium supplementation with cardiovascular risk is insufficient and inconclusive.

According to the Linus Pauling Institute, the National Osteoporosis Foundation (NOF) and the American Society for Preventive Cardiology (ASPC) concluded that calcium supplementation in generally healthy individuals was cardiovascular safe when total calcium intake did not exceed the upper limit. " (More on the high limit level below).

Possible side effects.

The tolerable upper intake level (UL) for calcium, which is defined as the maximum amount a person should take, is 2,500 mg per day for adults ages 19 to 50. For children 9 to 18 years old, this amount is 3,000 mg per day. For people age 51 and over, the allowed amount is 2000 mg per day. Consuming too much above the upper limit can lead to constipation and bloating.

Research shows that doses above 4,000 mg are associated with many health risks.

Risks of an excessive dose of calcium

  • Elevated levels of calcium in the blood
  • Kidney (kidney) damage
  • Milk alkaline syndrome (a condition in which there is too much calcium in the body)

Some people who take calcium supplements even in the recommended amounts may experience side effects, such as gas, bloating, constipation, or a combination of these symptoms. It has been suggested that calcium carbonate is more likely to cause these symptoms than calcium citrate.

Efforts to reduce symptoms include spreading calcium doses throughout the day and taking calcium with meals.

Additionally, excessive calcium intake can cause high blood calcium levels in a condition known as hypercalcemia. Hypercalcemia can cause kidney failure, vascular and soft tissue calcification, hypercalciuria (high levels of calcium in the urine), and kidney stones.

Drug interactions

If you are taking medications, you should contact your healthcare professional before starting calcium supplements, as calcium can interact with some medications. Calcium can interfere with the absorption of the following medications: salicylates, bisphosphonates, tetracyclines, thyroid hormones (syntroid, levotroid), fluoroquinolones (ciprofloxacin), and sotalol.

Also, some medications can interfere with calcium absorption. These include anticonvulsants, cholestyramine, corticosteroids, ciprofloxacin, tetracyclines, mineral oils, and stimulant laxatives. High doses of calcium increase the risk of milk-alkali syndrome in those taking thiazide diuretics and in people with kidney dysfunction.

Dosage and preparation

The amount of calcium a person needs depends on their age. The recommended diet (RDA) for calcium in the United States is 1,000 mg for adult men and women (women ages 19 to 50 and men ages 19 to 70) and 1,200 mg for the elderly (women over 50 and older men 70 years). .

To help achieve peak bone mass, children and adolescents between the ages of 9 and 18 should consume a total of 1,300 mg of calcium per day; this can be done with a supplemented diet.

Pregnant and lactating adolescents (ages 17-19) should consume a total of 1,300 mg of calcium per day, while pregnant and lactating adult women (ages 19 and older) should consume a total of 1,000 mg of calcium per day .

If you cannot meet your calcium needs from diet alone, you can use a calcium supplement. For maximum absorption, it is best to take 500 mg of calcium at a time.

It is best not to exceed 500 mg at a time. For example, if you are taking 1000 mg of calcium per day, you can split the dose (500 mg in the morning and 500 mg in the evening).

What to look for

Not all types of calcium contain the same amount of elemental calcium, the amount of calcium that is actually absorbed by the body. For example, calcium carbonate contains more elemental calcium than calcium gluconate .

Make sure the label of the calcium product of your choice indicates the amount of elemental calcium as well as the total amount of calcium. If you don't see the words elemental calcium, you may consider purchasing a different type of supplement.

Forms of calcium

The two main forms of calcium supplements are calcium carbonate (calcite) and calcium citrate (citracal).

Calcium carbonate is more readily available and must be taken with food due to its dependence on stomach acid for absorption. It contains 40 percent elemental calcium, which means it contains the highest concentration of calcium in supplement form for maximum absorption. In most cases, this type of calcium is taken more often than once a day and should be taken with meals.

It is generally affordable and is found in some over-the-counter antacid products (such as Tums and Rolaids). On average, each chewable tablet contains between 200 and 400 mg of elemental calcium.

On the other hand, calcium citrate can be taken with or without food and is considered the best supplement for people with achlorhydria (insufficient stomach acid), inflammatory bowel disease, or malabsorption. Fortified fruit juices often contain calcium malate citrate.

Several vitamins and minerals, vitamin D and magnesium, are important for the absorption of calcium. Therefore, you can find a calcium supplement that includes one or both to ensure you optimize your dosage .

Diet sources

To optimize your dietary calcium intake, try to eat two to three servings of dairy products a day, such as organic milk, yogurt, and cheese.

It is always good to get as much vitamins and minerals as possible from food.

If you don't consume dairy products, you can look to foods fortified with calcium, such as yogurt substitutes, nut milk, orange juice, cereals, and tofu.

Fatty fish (like salmon) also contain calcium. Leafy greens like kale, kale, and kale also contain calcium, but they are not as bioavailable, meaning they are not immediately absorbed for use in the body.

Other questions

How can I get the most out of calcium supplements?

Avoid calcium supplements when eating certain foods like wheat bran, spinach, and rhubarb. The types of acids in these foods (phytic acid, oxalic acid, and uronic acid) can interfere with calcium absorption.

Does sodium intake affect calcium absorption?

A diet rich in sodium can increase urinary calcium excretion. Some doctors advise postmenopausal women who have a sodium intake greater than 2,000 to 3,000 mg per day to increase their calcium intake to approximately 1,500 mg per day.

Get the word of drug information

Calcium is an essential mineral, yet the health benefits of calcium supplements are mixed. Some research suggests that calcium supplementation may improve bone mineral density and fractures, reduce the risk of colon cancer, and improve and prevent hypertension, although this is not conclusive. Before taking calcium supplements, it is important to discuss their use with your healthcare provider. The best way to absorb calcium is through diet foods.

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