What is the preferred calcium supplement between calcium aspartate and calcium carbonate?

Calcium Carbonate vs. Calcium Aspartate: Choosing the Optimal Calcium Supplement

Calcium carbonate is the preferred calcium supplement over calcium aspartate due to its higher elemental calcium content (40%), wide availability, and lower cost, though calcium citrate may be a better option for those with acid-reducing medication use or gastrointestinal issues.

Calcium Supplement Formulations

• Calcium carbonate is the most commonly used supplement, providing 40% elemental calcium by weight, making it cost-effective and widely available 1, 2
• Calcium citrate provides less elemental calcium (21%) but may be better absorbed when taken without food 1, 2
• Other less common forms include calcium lactate (13% elemental calcium) and calcium gluconate (9% elemental calcium) 1, 2
• Calcium aspartate is not specifically mentioned in major clinical guidelines for calcium supplementation 1

Absorption Considerations

• Calcium carbonate requires gastric acidity for optimal absorption and should be taken with meals 1, 3
• Calcium citrate absorption is less dependent on gastric acidity, making it suitable for patients on acid-reducing medications or those with achlorhydria 1, 3
• Meta-analysis shows calcium citrate is absorbed approximately 22-27% better than calcium carbonate, whether taken on an empty stomach or with meals 4
• However, some studies show minimal differences in absorption between calcium carbonate and citrate when taken with food 5

Dosing Recommendations

• If daily supplementation exceeds 500 mg of elemental calcium, divided doses are recommended to improve absorption and minimize gastrointestinal side effects 1
• Recommended daily calcium intake varies by age and sex: 1,000 mg for adults 19-50 years and men 51-70 years; 1,200 mg for women over 50 and men over 70 1
• Upper intake levels should not exceed 2,500 mg per day (2,000 mg per day in persons >50 years of age) 1

Special Populations

• For patients who have undergone bariatric surgery, calcium citrate may be preferred over calcium carbonate due to potentially better absorption 1
• For patients with chronic kidney disease, calcium carbonate is recommended for calcium supplementation 1
• For patients at risk of kidney stones, calcium citrate may be the preferred supplement 1

Side Effects and Considerations

• Calcium carbonate is more likely to cause constipation and bloating compared to other calcium supplements 1
• Calcium supplements may modestly increase the risk of nephrolithiasis compared to dietary calcium 1
• Some studies have raised concerns about potential cardiovascular risks with calcium supplements, though evidence remains inconsistent and inconclusive 1

Clinical Decision Algorithm

1. First, assess dietary calcium intake (assume ~300mg from non-dairy sources plus dairy intake) 1
2. Determine if supplementation is needed to reach recommended daily intake 1
3. For most patients, choose calcium carbonate taken with meals 1, 3
4. Consider calcium citrate instead if:
   • Patient is on acid-reducing medications 3, 6
   • Patient has gastrointestinal symptoms with calcium carbonate 1
   • Patient has difficulty taking supplements with meals 1
   • Patient has undergone bariatric surgery 1
   • Patient is at risk for kidney stones 1

Common Pitfalls

• Failing to consider total calcium intake from both diet and supplements 1
• Not advising patients to take calcium carbonate with meals 1, 3
• Prescribing doses exceeding 500 mg elemental calcium at one time, which may reduce absorption 1
• Not considering potential drug interactions between calcium supplements and other medications 7
• Overlooking that dietary sources of calcium are generally preferred over supplements when possible 1