From the Guidelines
Calcium citrate is the most effective calcium supplement for treating hypocalcemia, as it is well-absorbed on an empty or full stomach and does not require stomach acid for absorption. This makes it ideal for individuals who have undergone certain bariatric surgeries, such as sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB), as noted in the British Obesity and Metabolic Surgery Society guidelines 1.
When choosing a calcium supplement, it is essential to consider the formulation and dosing. Calcium citrate may be the preferred supplement for people at risk of developing kidney stones, as suggested by the guidelines 1. A typical dose is 500-600mg of elemental calcium taken twice daily (morning and evening) for better absorption. It is also crucial to look for supplements that contain vitamin D, usually 800-1000 IU daily, as it significantly enhances calcium absorption.
While calcium carbonate is a less expensive alternative that contains more elemental calcium per pill, it should be taken with food to aid absorption, as noted in the guidelines 1. However, the higher cost and lower calcium content by weight of calcium citrate should be weighed against its benefits, including better absorption and reduced risk of kidney stones. According to a study on calcium supplementation, calcium citrate bioavailability is not affected by meals, but its higher cost and lower calcium content may reduce acceptability and adherence 1.
In terms of dosing, most adults need 1000-1200mg of calcium daily from all sources combined, including diet. Side effects may include constipation or gas, which can be minimized by starting with a lower dose and gradually increasing it. Overall, calcium citrate is the recommended calcium supplement for treating hypocalcemia due to its superior absorption profile and potential benefits for individuals at risk of kidney stones.
From the Research
Forms of Calcium Supplements
- Calcium carbonate and calcium citrate are the most common forms of calcium supplements 2
- Calcium carbonate is the most cost-effective form and should be taken with a meal to ensure optimal absorption 2
- Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or who are taking histamine-2 blockers or protein-pump inhibitors 2
- Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements 2
- Hydroxyapatite is not recommended as a source of calcium due to limited research 2
Dosage and Absorption
- The maximum dose of elemental calcium that should be taken at a time is 500 mg 2
- A divided dose regimen (4x/d; i.e., with meals and at bedtime) results in substantially greater absorption of a supplement than does 1x/d dosing 3
- Gastric acid is not necessary for absorption of even poorly soluble preparations, so long as they are taken with meals 3
- Typical patients exhibit a wide range of absorption efficiencies, making it desirable to assess absorption fraction before beginning a supplement regimen 3
Safety and Potential Adverse Effects
- Potential adverse effects of calcium supplementation include gastrointestinal complaints 2
- Renal calculi in most studies have not been associated with calcium supplementation 2
- The risk of advanced and fatal prostate cancer has been associated with calcium intakes from food or supplements in amounts >1500 mg/d 2
- High doses of vitamin D supplementation with calcium may result in frequent hypercalciuria and hypercalcaemia, and may be associated with kidney stones 4, 5
- Long-term vitamin D supplementation resulted in increased risks of hypercalcemia and hypercalciuria, but did not increase risk of kidney stones 5
- Calcium supplementation in patients with chronic kidney disease may increase the risk of vascular calcification, and the upper limit of calcium intake should be reconsidered 6