Calcium Recommendations for Reproductive-Age Adults Trying to Conceive
For reproductive-age adults trying to conceive, aim for 1000 mg of elemental calcium daily through diet, and only supplement if dietary intake is inadequate—there is no evidence that calcium supplementation improves fertility outcomes, but adequate calcium intake is essential for maternal and fetal health once pregnancy is achieved. 1
Recommended Daily Intake
- Women aged 19-50 years (including those trying to conceive) should consume 1000 mg of elemental calcium per day 1
- This recommendation applies to the preconception period and continues through pregnancy and lactation 1
- The upper tolerable limit is 2500 mg per day for this age group—exceeding this increases risk of adverse effects 1
Prioritize Dietary Sources Over Supplements
- Calcium-rich foods and beverages are the preferred approach to meeting calcium requirements 1
- Typical dietary sources include dairy products (milk, yogurt, cheese) providing approximately 740 mg, plus 300 mg from non-dairy sources 1
- Average calcium consumption in young women in Western countries is approximately 800 mg daily, which falls short of the 1000 mg recommendation 2
When to Consider Supplementation
Supplements should only be considered when dietary intake is inadequate (<500-900 mg/day) 1, 3
Specific situations warranting supplementation include:
- Women with chronic autoimmune disorders 2
- Those on anticoagulation therapy during pregnancy 2
- Lactose intolerance 2
- Personal dietary preferences that exclude dairy products 2
Calcium and Fertility: The Evidence Gap
- There is no direct evidence that calcium supplementation improves fertility or conception rates 4
- One study examining infertile women undergoing assisted reproductive technology found no difference in serum calcium levels compared to fertile women 4
- Serum calcium levels remain stable during ovarian hyperstimulation for IVF, despite rising estrogen levels 4
Supplementation Protocol (If Needed)
If dietary intake is insufficient, follow this approach:
Formulation:
- Calcium carbonate is preferred due to 40% elemental calcium content, lower cost, and better cost-effectiveness 5, 3, 6
- Take calcium carbonate with meals to optimize absorption 1
- Calcium citrate (21% elemental calcium) is an alternative for those with GERD or on acid-suppressing medications 6
Dosing:
- Supplement with 500-1000 mg elemental calcium daily to reach the 1000 mg total daily goal 2
- Divide doses into increments of ≤500 mg per administration to maximize absorption 5, 3, 6
- For calcium carbonate: one 500-mg tablet provides 200 mg elemental calcium 1
Important Risks and Caveats
Potential risks of calcium supplementation include:
- Constipation and bloating are common side effects 1
- Modest increased risk of kidney stones (nephrolithiasis) with supplement use, but not with dietary calcium 1
- Potential cardiovascular risk remains inconsistent and inconclusive in the evidence 1
- Bone meal, oyster shell, and dolomite supplements may contain lead and should be avoided during pregnancy planning 1
Critical Pitfall to Avoid
Do not exceed 2500 mg total daily calcium intake from all sources combined 1
Women who consume adequate dietary calcium (≥800 mg/day) and add high-dose supplements risk exceeding safe limits, which increases the potential for adverse effects without additional benefit 1
Transition to Pregnancy
Once pregnancy is achieved, calcium requirements remain 1000 mg daily, but the rationale shifts to preventing preeclampsia and supporting fetal skeletal development 3, 7, 8
- In populations with low dietary calcium intake (<900 mg/day), supplementation with 1.5-2.0 g elemental calcium daily reduces preeclampsia risk by approximately 50% 3, 7, 9
- Women with adequate baseline intake may not require supplementation during pregnancy 8, 9
- The fetus requires 50-330 mg calcium daily for skeletal development, which is met through maternal physiological adaptations when intake is adequate 2, 8