Supplemental Calcium: Pros and Cons

One of the essential nutrients crucial for maintaining good bone and dental health is calcium. It is widely recognized that calcium is necessary for the proper functioning of the heart, muscles, and nerves. Several studies have also indicated that calcium and vitamin D may offer benefits beyond bone health. In the United States, millions of women take calcium supplements to strengthen their bones, especially after menopause when the risk of fractures increases. Furthermore, individuals with rheumatoid arthritis and other inflammatory conditions often take calcium supplements.

While most people obtain sufficient calcium through a healthy diet, those who don’t may need to consider taking calcium supplements. It is important for individuals to understand their specific calcium requirements and choose the most suitable supplements.

However, the use of calcium supplements is not suitable for everyone. For example, individuals with hypercalcemia, a medical condition characterized by excessive calcium levels in the blood, should avoid taking calcium supplements. In certain cases, an excess or deficiency of calcium from food or supplementation can be harmful.

This article provides a brief overview of the daily calcium requirements for humans, different types of calcium supplements, the role of calcium in nutrition, and the adverse effects of consuming too little or too much calcium.

Different Calcium Supplement Types

Calcium supplements are available in two main forms: citrate and carbonate. Considering that calcium carbonate is the most affordable option, it is a practical choice. Various calcium salts are found in calcium supplements, each containing a different amount of calcium. The most common calcium supplements are calcium carbonate, which contains 40% elemental calcium, calcium citrate, which contains 21% elemental calcium, calcium lactate, which contains 13% elemental calcium, and calcium gluconate, which contains 9% elemental calcium.

In addition, some calcium supplements may also contain magnesium or vitamin D. To determine the specific type and amount of calcium included in a product, it is important to carefully read the product labels and examine the supplement ingredients. This information is particularly crucial for individuals with dietary restrictions or health conditions.

Dosage and management

The daily recommended amount of calcium varies based on age and gender. During the ages of 18 to 25, the body’s bone mass reaches its peak and then gradually declines. For adult males, the recommended dietary allowance (RDA) for calcium is as follows: 1,000 mg for those between the ages of 19 and 70, and 1,200 mg for those over the age of 71. For females, the RDA for calcium is 1,000 mg for those under the age of 19 and 1,200 mg for those over the age of 51.

Unless specifically advised by a healthcare professional or nutritionist, individuals should not exceed a daily calcium intake of 1,200 mg from supplements. Most Americans typically obtain between 750 mg and 900 mg of calcium per day solely from their diet.

It is now known that calcium absorption greatly benefits from vitamin D (calciferol). Prior to 1997, the recommended daily allowance (RDA) for calcium and vitamin D was 200 IU (international units) for individuals under 50, 400 IU for those between 51 and 70, and 600 IU for those over 70. However, due to reduced vitamin D production in aging skin, the requirements increase with age. Since then, updated recommendations have been made, which will be explained further below.

Lack of calcium

Hypoparathyroidism, achlorhydria, chronic diarrhea, vitamin D insufficiency, steatorrhea, sprue, pregnancy and lactation, menopause, pancreatitis, renal failure, alkalosis, and hyperphosphatemia are conditions associated with calcium deficiency. In some cases, hypocalcemia (low calcium levels) can occur as a result of certain medications, such as certain diuretics and anticonvulsants, which may require calcium replacement therapy.

Low calcium intake can also be seen in individuals who follow a vegan diet, have lactose intolerance and avoid dairy products, consume high amounts of protein or sodium, have osteoporosis, undergo long-term corticosteroid treatment, or have certain bowel or digestive disorders like celiac disease or inflammatory bowel disease that impair calcium absorption. Calcium supplements can be beneficial in helping individuals meet their calcium requirements under such circumstances.

Sources of Calcium

Calcium is essential for supporting bone growth and maintenance to prevent fractures associated with osteoporosis. While dairy products are a good source of calcium, there are also non-dairy options such as cereals, figs, soft-boned fish, and calcium-fortified meals. However, even with a balanced diet, it may be challenging to obtain sufficient calcium on a daily basis.

Two natural sources of calcium are coral calcium and oyster shell calcium. Coral calcium is derived from fossilized coral sources, while oyster shell calcium comes from the shells of oysters. The body naturally undergoes a process called chelation to combine calcium with another substance, such as an amino acid, which aids in digestion. Coral calcium is also used in procedures like bone grafting and maxillofacial surgery.

Vitamin D plays a crucial role in the absorption of calcium and the maintenance of bone density. Therefore, some calcium supplements also include vitamin D. There are two forms of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 has a shorter shelf life compared to vitamin D3. Vitamin D can be obtained from sources such as egg yolks, canned salmon with bones, foods fortified with vitamin D, and exposure to sunlight. The recommended daily allowance (RDA) for vitamin D is 600 IU for individuals under the age of 70, including pregnant or nursing women, and 800 IU for those over the age of 71.

Vitamin K2 is another important nutrient for bone health. It has various isoforms or analogs, such as MK-4 to MK-10. Vitamin K2 significantly reduces the risk of osteoporosis and the calcification of arteries and soft tissues, which are common effects of aging. Vitamin K2 is found in animals and bacteria, particularly healthy probiotic bacteria in the gastrointestinal tract. However, the use of antibiotics can affect the production of vitamin K2 and hinder the growth of beneficial bacteria.

Although vitamin D3 has long been recognized as the bone vitamin for its role in activating the osteocalcin gene and quickly influencing bones, the slower-acting vitamin K2 has also been acknowledged as crucial for bone health. Both vitamins play a vital role in the complete replacement of the human skeleton, which occurs every 8 to 10 years. The recommended daily dosage of vitamin K2 for oral osteoporosis treatment is 45 mg.

Dietary considerations

When selecting a calcium supplement, it is important to consider the following factors:

  • Elemental Calcium: The amount of calcium that is actually absorbed by the body is crucial for bone development and overall health benefits. Reading the label on calcium supplements can help determine the amount of elemental calcium in each serving (e.g., number of tablets). For example, 1,250 mg of calcium carbonate contains 500 mg of elemental calcium (40 percent).
  • Supplement Selection: Some people may experience side effects such as gas, constipation, or bloating with certain calcium supplements. It may be necessary to try different brands or varieties to determine which calcium supplement is best tolerated. Calcium carbonate has the highest calcium content and is the least expensive but may cause constipation. Calcium phosphate is more expensive but does not result in gas or constipation. Calcium citrate is the most readily absorbed form of calcium and does not require stomach acid for absorption, but it is more costly and contains less elemental calcium. Women should ensure they obtain enough calcium from their diet and supplements.
  • Dosage Forms: Calcium supplements are available in various forms such as chewable tablets, capsules, liquids, and powders. People who have difficulty swallowing tablets can opt for chewable or liquid calcium supplements.
  • Drug Interactions: Calcium supplements may interact with certain prescription drugs, including calcium channel blockers, synthetic thyroid hormones, bisphosphonates, and antibiotics. It is recommended to consult with a pharmacist to discuss potential drug interactions and seek advice on calcium supplements.
  • Absorption: Calcium supplements should be given in smaller quantities (e.g., 500 mg at a time) to enhance absorption by the body. Calcium citrate is a type of calcium supplement that is equally absorbed with or without food and is recommended for individuals with inflammatory bowel disease or low stomach acid, such as those over 50 years old, taking antacids, or using proton pump inhibitors.
  • Cost and Quality: Supplement manufacturers are required by the Federal Trade Commission to ensure the safety of their products and to make accurate claims. Some companies have their products independently tested according to U.S. Pharmacopeia (USP) standards. The USP mark indicates that a supplement meets quality assurance requirements.

Considering these factors can help in choosing an appropriate calcium supplement that meets individual needs and preferences.

Cardiovascular Effects of Calcium Supplementation

Concerns have been raised about the potential negative effects of high calcium intake on cardiovascular health in the elderly, specifically due to the calcification of arteries and veins. These effects may be attributed to various pathophysiological pathways that affect vascular calcification, vascular cell function, and blood coagulation. However, recent research has not found an increased risk of heart attack or stroke in women who took calcium supplements over a 24-year follow-up period.

Some scientists argue that there may be no overall benefits from calcium supplements, as they may slightly reduce fracture risk but slightly increase cardiovascular risk. They suggest that obtaining calcium from food sources might be preferable to supplements, as they seem to have similar effects on bone density and are not associated with negative cardiovascular effects. Further research is needed to prospectively examine the impact of calcium or calcium + vitamin D supplementation beyond bone health. Medical professionals still have uncertainties about the effects of calcium supplements on women.

It is important to note that individual circumstances and medical advice should be taken into consideration when making decisions about calcium supplementation. Consulting with healthcare professionals can provide personalized guidance based on an individual’s specific health needs and concerns.

Calculating Calcium Levels in Coronary Arteries

In older individuals, calcium deposits can be observed throughout the body. A coronary calcium scan is commonly performed to detect calcium deposits within the plaque on the inner walls of the heart’s arteries. The scores obtained from a coronary calcium scan can reach as high as 400. A calcium score of zero indicates the absence of any noticeable plaque, while a score of 400 or higher suggests severe narrowing of the coronary arteries and the presence of atherosclerotic plaque.

Calcification of arterial walls is prevalent in individuals aged 65 and above. Women over the age of 50 often experience breast calcification. Since calcification consists of calcium phosphate, which is the same as that found in bones, it can be clearly visible on X-ray images.

Coronary calcium, which only occurs in atherosclerotic arteries and is absent in normal vessel walls, plays a role in the development of atherosclerosis. A calcium score, which measures the amount of calcium in the coronary artery walls, appears to be a more accurate predictor of cardiovascular disease risk compared to traditional risk factors.

Getting Balance

Low Calcium Intake Risks

Calcium is essential for maintaining strong bones, teeth, and normal muscle and nerve function. However, inadequate calcium levels can lead to various health issues. These include:

  1. Impaired growth: Insufficient calcium intake in both children and adults can hinder reaching their full adult height potential, increasing the risk of osteoporosis and hip fractures.
  2. Disruptions in blood calcium levels: Normal blood calcium levels are regulated by the actions of parathyroid hormone, the kidneys, and the intestines. In adults, serum calcium levels should range from 4.5 to 5.5 mEq/L. When calcium levels drop, it can cause symptoms related to the decrease in ionized (free) calcium, which is the metabolically active form of calcium.
  3. Causes of hypocalcemia: Hypocalcemia, or low levels of calcium, can be caused by various factors such as limited calcium intake, deficiency of vitamin D or K2, chronic renal failure, hypoparathyroidism, and reduced calcium absorption.

Risks of High Calcium Intake:

While the body has mechanisms to regulate calcium intake and maintenance, high calcium levels can still occur due to different factors. Elevated blood calcium levels can result from underlying illnesses, drug interactions, or excessive use of calcium supplements.

Excessive calcium intake can pose risks to health and should be treated medically. Although calcium from food sources is generally safe, consuming too much calcium, either through diet or supplements, does not provide additional bone protection. Instead, it can lead to kidney stones, prostate cancer, constipation, calcium buildup in blood vessels, and decreased absorption of iron and zinc.

Increasing calcium levels above the recommended daily allowance (RDA) through supplements or calcium-fortified foods should be done cautiously to avoid surpassing the advised dosage.

Overall, maintaining a balanced and adequate intake of calcium is crucial for optimal health, while excessive or insufficient levels can have negative consequences.


The best approach to address calcium deficiency is through prevention. Modifying risk factors is crucial, and pharmacists can play a significant role in this regard. They are qualified to recommend appropriate calcium and vitamin D supplements. Specifically, women should focus on consuming calcium- and vitamin D-rich foods and beverages, quitting smoking, and engaging in weight-bearing and muscle-strengthening activities if they are at risk of low calcium levels. Monitoring body mass index as one ages is also important to reduce the risk of bone fractures.

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