How do I replenish calcium levels?

How to Replete Calcium

Prioritize dietary calcium sources, aiming for 1000-1200 mg/day from dairy products, fortified foods, and calcium-rich vegetables, and only use supplements (calcium carbonate with meals or calcium citrate without food) when dietary intake is insufficient. 1

Target Daily Calcium Intake

The recommended dietary allowance varies by age and sex:

• Adults aged 19-50 years and men 19-70 years: 1000 mg/day 1
• Women over 50 years and men over 70 years: 1200 mg/day 1
• Adolescents: 1300 mg/day (North America) or 1000 mg/day (UK) 1
• Athletes or those with relative energy deficiency: Consider 1500 mg/day 1
• Upper limit: Do not exceed 2500 mg/day for adults under 50, or 2000 mg/day for those over 50 1

Dietary Sources: First-Line Approach

Food sources are strongly preferred over supplements because they provide additional essential nutrients and improve overall diet quality. 2, 3

High-Yield Calcium-Rich Foods

The following foods provide substantial calcium per serving 1, 4:

• Dairy products (most bioavailable source):

  • Whole or skimmed milk (200 mL): 240 mg 1
  • Hard cheese like cheddar (30 g): 220 mg 1
  • Yogurt (120 g): 200 mg 1
  • Calcium-enriched soy milk (200 mL): 240 mg 1

• Fish with bones:

  • Sardines with bones (½ tin): 258 mg 1

• Vegetables and plant sources:

  • Kale (67 g): 100 mg 1
  • Orange (1 medium): 75 mg 1
  • Broccoli (2 spears): 34 mg 1
  • Green leafy vegetables, nuts, and soya beans 1

Important caveat: Some plant components like phytates in cereals and oxalates in spinach reduce calcium bioavailability, making exclusive plant-based calcium repletion impractical without fortified foods or supplements. 5, 6

Supplement Selection: When Dietary Intake is Inadequate

Use supplements only when you cannot achieve adequate intake through food sources. 1, 3

Choosing the Right Supplement Form

• Calcium carbonate 1, 3:

  • Most cost-effective option 3
  • Must be taken with meals to ensure optimal absorption 1, 3
  • Requires gastric acid for dissolution 5
  • Not suitable for patients with achlorhydria or those taking H2-blockers or proton-pump inhibitors 3

• Calcium citrate 1, 3:

  • Can be taken without food 3
  • Preferred for patients with achlorhydria or on acid-suppressing medications 3
  • Well absorbed but more expensive than carbonate 1

• Avoid: Calcium lactate and calcium gluconate are less concentrated and not practical for oral supplementation 3

Dosing Strategy

Never take more than 500 mg of elemental calcium at one time to optimize absorption. 3 Divide total daily supplementation into multiple doses throughout the day.

Special Populations and Considerations

Chronic Kidney Disease Patients

In CKD stages 3-4, maintain total elemental calcium intake at 800-1000 mg/day (including dietary calcium, supplements, and calcium-based phosphate binders). 7

• Monitor serum calcium, phosphate, and PTH levels regularly 7
• Keep corrected total serum calcium at 8.4-9.5 mg/dL (lower end of normal range) 1
• Maintain calcium-phosphorus product below 55 mg²/dL² 1
• If corrected calcium exceeds 10.2 mg/dL: Reduce or discontinue calcium-based binders and vitamin D sterols 1

Athletes and High Sweat Loss

Athletes training in hot environments may need up to 1500 mg/day due to dermal calcium losses through sweat. 1 Consider taking 1350 mg of calcium 90 minutes before prolonged exercise to attenuate bone resorption markers. 1

Vegetarian/Vegan Diets

Plant-based diets require careful planning due to lower calcium bioavailability. 6 Fortified foods or supplements are typically necessary to achieve adequate calcium balance on an exclusively plant-based diet. 6

Enhancing Calcium Absorption

• Co-administer vitamin D: Ensure adequate vitamin D status (25-hydroxyvitamin D >30 ng/mL) as it is essential for calcium absorption 1, 7
• Avoid interference: Limit tea and coffee consumption around meal times as they impair calcium absorption 1
• Moderate protein and sodium: High protein and salt intake increase urinary calcium losses 5, 6

Monitoring and Safety

• Assess calcium intake at least annually 1
• Monitor for side effects: constipation, bloating, and rarely nephrolithiasis 1, 3
• Cardiovascular risk: Recent studies suggest potential increased cardiovascular risk with supplementation, though evidence remains inconsistent 1
• Choose U.S. Pharmacopeia-verified supplements to ensure quality 3

Common Pitfalls to Avoid

• Do not exceed 2000-2500 mg/day total intake: Risk of hypercalcemia, nephrolithiasis, and potentially cardiovascular events 1
• Do not take calcium carbonate on an empty stomach: Absorption will be poor, especially in those with reduced gastric acid 3, 5
• Do not rely solely on supplements: They cannot correct poor dietary patterns and lack the additional nutrients found in calcium-rich foods 2
• Do not ignore vitamin D status: Calcium repletion is ineffective without adequate vitamin D 1, 7