Mineral

    Calcium

    Calcium carbonate/citrate

    TL;DR

    Calcium is best obtained from food; supplements are for people who genuinely cannot reach 1000-1200 mg/day. Large single doses raise kidney stone risk and possibly vascular calcification, so split doses at 500 mg or less and always pair with adequate vitamin D and vitamin K2.

    Ideal For

    • Postmenopausal women with dietary intake below 700 mg/day
    • Adults over 70 with limited dairy intake
    • Pregnant women in low-calcium-intake populations
    • People with premenstrual syndrome
    • Those on long-term corticosteroids
    • People on PPIs, who should use the citrate form

    Avoid If

    • You have hypercalcaemia or primary hyperparathyroidism
    • You have a history of calcium-containing kidney stones without urology input
    • You have sarcoidosis or another granulomatous disease
    • You already exceed 1200 mg/day from food
    • You have severe renal impairment without nephrology supervision

    Frequently Asked Questions

    Do calcium supplements cause heart attacks?
    The signal appeared in reanalyses of trials using large single doses without vitamin D and has not been confirmed in dietary calcium studies. Splitting doses at 500 mg or less and prioritising food keeps the question largely moot.
    Citrate or carbonate?
    Carbonate is cheaper and fine with meals if your stomach acid is normal. Citrate is the choice if you take a PPI, have had bariatric surgery, or find carbonate constipating.
    Do I need vitamin K2 with it?
    K2 activates osteocalcin and matrix Gla protein, which direct calcium into bone and away from arteries. The fracture evidence is mixed but the rationale is sound and the risk is negligible.
    Does calcium prevent fractures on its own?
    Barely. The fracture benefit in trials comes from calcium plus vitamin D in older adults with genuinely low intake, not from calcium alone in replete people.

    Overview

    Calcium is the most abundant mineral in the body and 99% of it is structural, held in the hydroxyapatite lattice of bone. The remaining 1% in blood and cells is defended so tightly by parathyroid hormone, calcitriol and calcitonin that serum calcium tells you almost nothing about intake — when dietary calcium falls, the skeleton is quietly mined to keep it constant.

    That regulatory tightness shapes how supplements should be used. Absorption is saturable: roughly 35% of a 300 mg dose is absorbed but the fraction falls steeply above 500 mg, so a single 1000 mg tablet is both wasteful and more likely to cause the sharp plasma rise that has been linked with vascular calcification in some analyses. Trials of high-dose calcium alone have shown small increases in kidney stones and, in a contested set of analyses, myocardial infarction — a signal not seen with dietary calcium.

    The evidence that stands up is for calcium plus vitamin D in older adults with low intake, where fracture risk falls modestly, and for calcium in pregnancy, where 1.5-2 g/day meaningfully reduces pre-eclampsia risk in low-intake populations. Calcium also has good evidence in premenstrual syndrome at 1000-1200 mg/day. For everyone else, dairy, tinned fish with bones, tofu set with calcium sulfate, and leafy greens do the job better than a pill.

    How It Works

    • Forms the hydroxyapatite mineral matrix that gives bone compressive strength
    • Triggers actin-myosin cross-bridge cycling in muscle contraction
    • Mediates neurotransmitter release at synaptic terminals
    • Serves as an essential cofactor in the coagulation cascade
    • Suppresses parathyroid hormone, reducing bone resorption when intake is adequate
    • Binds oxalate and fatty acids in the gut, lowering their absorption

    Quick Facts

    • Builds strong bones
    • Supports muscle function
    • Essential for nerve signaling
    • Required for blood clotting

    Supporting Research
    68 studies

    Dietary L-lysine and calcium metabolism in humans

    Score: 4/10
    1992
    crossover
    n=30

    Civitelli R, Villareal DT, Agnusdei D

    L-lysine supplementation increased intestinal calcium absorption and reduced urinary calcium excretion in healthy women.

    View source

    Vitex agnus-castus extract Ze 440 relaxes human myometrium through modulation of calcium channels

    Score: 3/10
    2019
    observational

    Mohr T, Kaufmann U, Schlichting J +4 more

    Ze 440 and isolated constituents produced concentration-dependent relaxation of pre-contracted human uterine muscle strips, an effect consistent with blockade of voltage-gated calcium channel-mediated contraction.

    View source

    Citrate salts for preventing and treating calcium containing kidney stones in adults

    Score: 8/10
    2015
    systematic_review

    Phillips R, Hanchanale VS, Myatt A +3 more

    Citrate salts reduced new calcium stone formation and slowed growth of residual stones compared with placebo or no treatment, with gastrointestinal upset the main adverse effect driving withdrawal.

    View source

    Interventions for leg cramps in pregnancy

    Score: 8/10
    2020
    systematic_review
    n=576

    Luo L, et al

    Across 8 trials (576 women), oral magnesium may reduce leg cramp frequency versus placebo in some trials but results were inconsistent; oral calcium showed no clear benefit; vitamin B complex and vitamin C evidence was very low certainty. No intervention was supported by high-quality evidence.

    View source

    Crucial Role of Vitamin D in the Musculoskeletal System

    Score: 4/10
    2016

    Wintermeyer E, Ihle C, Ehnert S +6 more

    Vitamin D is biologically inert until hydroxylated in liver and kidney to calcitriol, which drives intestinal calcium absorption and bone mineralisation. Deficiency causes rickets and osteomalacia and is associated with reduced muscle strength, impaired fracture healing and higher fall risk. The review reports benefit of correcting deficiency for bone healing and musculoskeletal function, and notes deficiency is highly prevalent in trauma and orthopaedic patients.

    View source

    A review of treatment of premenstrual syndrome and premenstrual dysphoric disorder

    Score: 5/10
    2003
    systematic_review

    Kaur G, Gonsalves L

    Calcium showed the most consistent benefit for irritability and mood symptoms; magnesium and B6 evidence was weaker and mixed.

    View source

    Demographic Characteristics and Association of Serum Vitamin B12, Ferritin and Thyroid Function with Premature Canities in Indian Patients

    Score: 5/10
    2017
    observational
    n=71

    Sonthalia S

    Among 71 Indian patients with premature greying, low serum vitamin B12 was common and serum ferritin and calcium levels were frequently reduced compared with reference values; thyroid dysfunction was uncommon, and a family history of premature canities was the strongest associated factor.

    View source

    Magnesium, Calcium, Potassium, Sodium, Phosphorus, Selenium, Zinc, and Chromium Levels in Alcohol Use Disorder: A Review

    Score: 6/10
    2020
    systematic_review

    Baj J

    Review of mineral status in alcohol use disorder found consistently low magnesium, zinc and selenium levels and frequently disturbed calcium, potassium, sodium and phosphate balance, driven by poor intake, gastrointestinal losses, renal wasting and liver dysfunction; deficiencies were linked to withdrawal severity, neuropathy, arrhythmia risk and refeeding complications.

    View source

    Diet, fluid, or supplements for secondary prevention of nephrolithiasis: a systematic review and meta-analysis of randomized trials

    Score: 8/10
    2009
    meta_analysis

    Fink HA, Akornor JW, Garimella PS +5 more

    Meta-analysis of randomised trials in recurrent kidney stone formers found increased fluid intake roughly halved stone recurrence, and among supplements thiazides, citrate salts and allopurinol reduced recurrence in calcium stone formers; low-animal-protein/high-fibre diets alone did not reduce recurrence and dietary calcium restriction was not beneficial.

    View source

    Dietary boron: progress in establishing essential roles in human physiology

    Score: 4/10
    2012
    systematic_review

    Hunt, C.D.

    This review of human and animal data found boron influences calcium, magnesium and vitamin D metabolism and steroid hormone levels, with depletion-repletion studies suggesting boron may reduce urinary calcium loss, but no clinical trials demonstrating reduced fracture risk or improved bone mineral density in humans.

    View source

    Vitamin D with or without calcium supplementation for prevention of cancer and fractures: an updated meta-analysis for the U.S. Preventive Services Task Force

    Score: 9/10
    2011

    Chung M, Lee J, Terasawa T +2 more

    This AHRQ-derived evidence review found that vitamin D combined with calcium modestly reduces fracture risk in institutionalised older adults, while evidence for vitamin D alone and for non-skeletal outcomes (cancer, cardiovascular disease, immune function) was inconsistent and largely inconclusive. Serum 25(OH)D thresholds for these outcomes could not be established.

    View source

    Vitamin K supplementation and progression of coronary artery calcium in older men and women

    Score: 8/10
    2009
    rct
    n=388

    Shea MK, O'Donnell CJ, Hoffmann U +6 more

    No difference in overall calcium progression, though a per-protocol analysis of adherent participants showed less progression among those with pre-existing calcification.

    View source

    Pivotal role of boron supplementation on bone health: A narrative review

    Score: 5/10
    2020
    systematic_review

    Rondanelli M, Faliva MA, Peroni G +1 more

    Available human studies suggest boron influences calcium, magnesium and vitamin D metabolism relevant to bone, but no dosing recommendation can be established from current data.

    View source

    Spinal bone loss in postmenopausal women supplemented with calcium and trace minerals

    Score: 5/10
    1994
    rct
    n=59

    Strause L, Saltman P, Smith KT

    Calcium plus trace minerals including manganese reduced spinal bone loss more than calcium alone over two years.

    View source

    Choline-stabilized orthosilicic acid supplementation as an adjunct to calcium/vitamin D3 stimulates markers of bone formation in osteopenic females: a randomized, placebo-controlled trial

    Score: 7/10
    2008
    rct
    n=136

    Spector TD, Calomme MR, Anderson SH

    Bone formation marker PINP rose significantly in the 6 and 12 mg silicon arms; femoral and lumbar BMD changes did not reach significance.

    View source

    Impact of Frequency of Multi-Vitamin/Multi-Mineral Supplement Intake on Nutritional Adequacy and Nutrient Deficiencies in U.S. Adults

    Score: 7/10
    2017
    systematic_review

    Blumberg JB, Frei BB, Fulgoni VL +2 more

    Supplement users had markedly lower prevalence of inadequate intakes for vitamins A, C, D, E, calcium and magnesium.

    View source

    Serum levels of phosphorus, parathyroid hormone, and calcium and risks of death and cardiovascular disease in individuals with chronic kidney disease: a systematic review and meta-analysis

    Score: 8/10
    2011
    meta_analysis
    n=327644

    Palmer SC, Hayen A, Macaskill P +4 more

    Each 1 mg/dL increase in serum phosphorus was associated with an 18% higher risk of death in people with chronic kidney disease

    View source

    Association among dietary supplement use, nutrient intake, and mortality among US adults: a cohort study

    Score: 7/10
    2019
    cohort
    n=30899

    Chen F, Du M, Blumberg JB

    Nutrient adequacy from food, but not from supplements, was associated with reduced all-cause mortality; excess calcium from supplements was linked to higher cancer mortality.

    View source

    Growing Evidence for Human Health Benefits of Boron

    Score: 5/10
    2011
    systematic_review

    Nielsen FH, Meacham SL

    Boron intakes above about 1 mg/day are associated with improved calcium and magnesium metabolism, bone strength and reduced inflammatory markers in experimental and observational work.

    View source

    Calcium channel blockers for primary Raynaud's phenomenon

    Score: 8/10
    2016
    systematic_review
    n=296

    Ennis H, Hughes M, Anderson ME

    Calcium channel blockers produced a small reduction in attack frequency, with low-quality evidence and frequent side effects.

    View source

    Calcium, vitamin D, or combined supplementation to prevent fractures and falls: systematic review and meta-analysis

    Score: 10/10
    2026
    meta_analysis
    n=153902

    Massé O, Mercurio CM, Dupuis S +4 more

    little to no effect was found from use of calcium supplements

    View source

    Vitamin D3 and calcium to prevent hip fractures in elderly women

    Score: 8/10
    1992
    rct
    n=3270

    Chapuy MC, Arlot ME, Duboeuf F +4 more

    the number of hip fractures was 43 percent lower (P = 0.043)

    View source

    Urinary tract stone occurrence in the Women's Health Initiative (WHI) randomized clinical trial of calcium and vitamin D supplements

    Score: 8/10
    2011
    rct
    n=36282

    Wallace RB, Wactawski-Wende J, O'Sullivan MJ +4 more

    associated with an increase in the number of self-reported urinary tract stones

    View source

    Calcium plus vitamin D supplementation and the risk of fractures

    Score: 9/10
    2006
    rct
    n=36282

    Jackson RD, LaCroix AZ, Gass M +4 more

    did not significantly reduce hip fracture, and increased the risk of kidney stones

    View source

    Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men

    Score: 10/10
    2014
    meta_analysis
    n=91791

    Avenell A, Mak JC, O'Connell D

    vitamin D plus calcium results in a small reduction in hip fracture risk

    View source

    Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis

    Score: 9/10
    2017
    meta_analysis
    n=51145

    Zhao JG, Zeng XT, Wang J +1 more

    There was no significant association of calcium or vitamin D with risk of hip fracture

    View source

    Schedule of taking calcium supplement and the risk of nephrolithiasis

    Score: 5/10
    2004
    crossover
    n=32

    Domrongkitchaiporn S, Sopassathit W, Stitchantrakul W +3 more

    Calcium supplement should be taken with meal in order to avoid increasing the risk

    View source

    Effects of calcium supplementation on clinical fracture and bone structure: results of a 5-year, double-blind, placebo-controlled trial in elderly women

    Score: 8/10
    2006
    rct
    n=1460

    Prince RL, Devine A, Dhaliwal SS +1 more

    calcium supplementation did not significantly reduce fracture risk

    View source

    Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis

    Score: 8/10
    2019
    meta_analysis

    Yao P, Bennett D, Mafham M +4 more

    daily supplementation with both vitamin D and calcium was a more promising strategy

    View source

    A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones

    Score: 6/10
    1993
    cohort
    n=45619

    Curhan GC, Willett WC, Rimm EB +1 more

    A high dietary calcium intake decreases the risk of symptomatic kidney stones

    View source

    Dietary factors and the risk of incident kidney stones in younger women: Nurses' Health Study II

    Score: 6/10
    2004
    cohort
    n=96245

    Curhan GC, Willett WC, Knight EL +1 more

    supplemental calcium is not associated with risk

    View source

    Vitamin D Supplementation and Fractures in Adults: A Systematic Umbrella Review of Meta-Analyses of Controlled Trials

    Score: 7/10
    2022
    systematic_review

    Chakhtoura M, Bacha DS, Gharios C +4 more

    Ca/D reduces the risk of hip and any fractures

    View source

    Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis

    Score: 8/10
    2007
    meta_analysis
    n=63897

    Tang BM, Eslick GD, Nowson C +2 more

    treatment was associated with a 12% risk reduction in fractures of all types

    View source

    Calcium supplementation and kidney stone risk in osteoporosis: a systematic literature review

    Score: 6/10
    2012
    systematic_review

    Candelas G, Martinez-Lopez JA, Rosario MP +2 more

    does not significantly increase the risk of nephrolithiasis or renal colic

    View source

    Calcium plus vitamin D supplementation and risk of fractures: an updated meta-analysis from the National Osteoporosis Foundation

    Score: 7/10
    2016
    meta_analysis
    n=30970

    Weaver CM, Alexander DD, Boushey CJ +4 more

    statistically significant 15 % reduced risk of total fractures

    View source

    Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up

    Score: 6/10
    2004
    cohort
    n=45619

    Taylor EN, Stampfer MJ, Curhan GC

    the association between calcium intake and kidney stone formation varies with age

    View source

    Dietary calcium from dairy and nondairy sources, and risk of symptomatic kidney stones

    Score: 6/10
    2013
    cohort
    n=226627

    Taylor EN, Curhan GC

    Higher dietary calcium from nondairy or dairy sources is independently associated with a lower kidney stone risk

    View source

    Impact of nutritional factors on incident kidney stone formation: a report from the WHI OS

    Score: 5/10
    2012
    cohort
    n=78293

    Sorensen MD, Kahn AJ, Reiner AP +4 more

    Greater dietary calcium intake significantly decreased the risk of incident kidney stones

    View source

    Pathophysiology and Treatment of Enteric Hyperoxaluria

    Score: 6/10
    2021
    systematic_review

    Witting C, Langman CB, Assimos D +4 more

    use of calcium salts to bind oxalate in the gut

    View source

    Prevention of Recurrent Nephrolithiasis in Adults and Children : A Systematic Review

    Score: 8/10
    2026
    systematic_review

    Asher GN, Viprakasit DP, Aymes SE +4 more

    a diet with normal to high calcium, low protein, and low sodium

    View source

    Impact of calcium intake and intestinal calcium absorption on kidney stones in older women: the study of osteoporotic fractures

    Score: 4/10
    2012
    observational
    n=7982

    Sorensen MD, Eisner BH, Stone KL +4 more

    Dietary and supplemental calcium decrease fractional calcium absorption, and may protect against nephrolithiasis

    View source

    Hypercalcemia, hypercalciuria, and kidney stones in long-term studies of vitamin D supplementation: a systematic review and meta-analysis

    Score: 8/10
    2016
    meta_analysis
    n=19833

    Malihi Z, Wu Z, Stewart AW +2 more

    not modified by baseline 25-hydroxyvitamin D, vitamin D dose and duration, or calcium co-supplementation

    View source

    Calcium supplementation and incident kidney stone risk: a systematic review

    Score: 4/10
    2008
    systematic_review

    Heaney RP

    most of the studies show no increase in stone risk with high calcium intake

    View source

    Effect of dietary changes on urinary oxalate excretion and calcium oxalate supersaturation in patients with hyperoxaluric stone formation

    Score: 3/10
    2009
    observational
    n=22

    Penniston KL, Nakada SY

    Gastrointestinal binding of oxalate by calcium is an effective clinical strategy for hyperoxaluria

    View source

    Stone forming risk of calcium citrate supplementation in healthy postmenopausal women

    Score: 4/10
    2004
    crossover
    n=18

    Sakhaee K, Poindexter JR, Griffith CS +1 more

    Calcium citrate supplementation does not increase the risk of stone formation in healthy postmenopausal women

    View source

    Two-year randomized controlled trial of vitamin K1 (phylloquinone) and vitamin D3 plus calcium on the bone health of older women

    Score: 7/10
    2007
    rct
    n=244

    Bolton-Smith C, McMurdo ME, Paterson CR +4 more

    10 microg (400 IU) vitamin D(3) plus 1000 mg calcium/day

    View source

    Vitamin K1 supplementation retards bone loss in postmenopausal women between 50 and 60 years of age

    Score: 7/10
    2003
    rct
    n=181

    Braam LA, Knapen MH, Geusens P +4 more

    calcium, magnesium, zinc, and vitamin D (MD group)

    View source

    Calcium intake and risk of fracture: systematic review

    Score: 9/10
    2015
    meta_analysis

    Bolland MJ, Leung W, Tai V +4 more

    Dietary calcium intake was not associated with fracture risk, and calcium supplements produced inconsistent and clinically unimportant reductions in total fracture risk with no reduction in hip fracture.

    View source

    A pilot study to compare fluoxetine, calcium, and placebo in the treatment of premenstrual syndrome

    Score: 6/10
    2013
    rct
    n=39

    Yonkers KA, et al.

    Fluoxetine had clear therapeutic benefit for premenstrual syndrome, whereas the effect of calcium was much smaller.

    View source

    Calcium carbonate and the premenstrual syndrome: effects on premenstrual and menstrual symptoms

    Score: 8/10
    1998
    rct
    n=466

    Thys-Jacobs S, Starkey P, Bernstein D +1 more

    Calcium supplementation is a simple and effective treatment in premenstrual syndrome, resulting in a major reduction in overall luteal phase symptoms.

    View source

    Prolonged effect of calcium supplementation on risk of colorectal adenomas in a randomized trial

    Score: 8/10
    2007
    rct
    n=930

    Grau MV, Baron JA, Sandler RS +2 more

    930 subjects with a previous colorectal adenoma were randomly assigned ... to receive placebo or 1200 mg of elemental calcium daily for 4 years

    View source

    Association of Epidemiological and Biochemical Factors with Premature Graying of Hair: A Case-Control Study

    Score: 6/10
    2018
    observational
    n=240

    Sharma N, Dogra D

    Significantly, lower levels of serum calcium, ferritin, Vitamin B12 were observed among cases.

    View source

    Long-Term Effect of Randomization to Calcium and Vitamin D Supplementation on Health in Older Women: Postintervention Follow-up of a Randomized Clinical Trial

    Score: 8/10
    2024
    rct
    n=36282

    Thomson CA, et al

    Calcium and vitamin D supplements seemed to reduce cancer mortality and increase CVD mortality after more than 20 years of follow-up.

    View source

    Bisphosphonates for steroid-induced osteoporosis

    Score: 9/10
    2016
    systematic_review
    n=3075

    Allen CS, Yeung JH, Vandermeer B

    Bisphosphonates, with calcium and vitamin D, increase bone mineral density and reduce vertebral fractures in patients receiving glucocorticoids.

    View source

    The effect of Vitamin D and calcium plus Vitamin D on leg cramps in pregnant women: A randomized controlled trial

    Score: 6/10
    2017
    rct
    n=126

    Mansouri A, et al

    The results of this study showed that the calcium-Vitamin D and the Vitamin D supplements have no effect on the frequency, length, and pain intensity of leg cramps during the 6 weeks of the study.

    View source

    Bones of contention: bone mineral density recovery in celiac disease - a systematic review

    Score: 6/10
    2015
    systematic_review
    n=1000

    Grace-Farfaglia P

    Calcium repletion supports bone density recovery alongside a strict gluten-free diet.

    View source

    Prevention of benign paroxysmal positional vertigo with vitamin D supplementation: A randomized trial

    Score: 8/10
    2020
    rct
    n=957

    Jeong SH, Kim JS, Kim HJ

    Combined vitamin D and calcium supplementation reduced recurrence of benign paroxysmal positional vertigo.

    View source

    Calcium intake and bone mineral density: systematic review and meta-analysis

    Score: 9/10
    2015
    meta_analysis

    Tai V, Leung W, Grey A +2 more

    Increasing calcium intake from diet or supplements produced small one-off increases in bone mineral density of about 1-2% that did not accumulate over time.

    View source

    Effect of Combined Use of Calcium and Vitamin B6 on Premenstrual Syndrome Symptoms: a Randomized Clinical Trial

    Score: 6/10
    2016
    rct
    n=76

    Masoumi SZ, et al.

    using of combination of calcium and vitamin B6 leads to better controlling of the premenstrual syndrome symptoms.

    View source

    Herbs, vitamins and minerals in the treatment of premenstrual syndrome: a systematic review

    Score: 7/10
    2009
    systematic_review

    Whelan AM, Jurgens TM, Naylor H

    To identify herbs, vitamins and minerals advocated for the treatment of PMS and/or PMDD and to systematically review evidence from randomized controlled trials (RCTs) to determine their efficacy in reducing severity of PMS/PMDD symptoms.

    View source

    Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria

    Score: 9/10
    2002
    rct
    n=120

    Borghi L, et al.

    In men with recurrent calcium oxalate stones and hypercalciuria, restricted intake of animal protein and salt, combined with a normal calcium intake, provides greater protection than the traditional low-calcium diet.

    View source

    Epidemiological and investigative study of premature graying of hair in higher secondary and pre-university school children

    Score: 5/10
    2013
    observational
    n=70

    Bhat RM

    S. Ca, S. Ferritin, vitamin D3 may play a role in premature graying of hair.

    View source

    Effects of alendronate and alfacalcidol on bone in patients with myasthenia gravis initiating glucocorticoids treatment

    Score: 7/10
    2018
    rct
    n=75

    Lv L, et al

    However, treatment with alfacalcidol alone failed to prevent bone loss in patients with MG receiving glucocorticoid therapy.

    View source

    Self-reported sleep bruxism is associated with vitamin D deficiency and low dietary calcium intake: a case-control study

    Score: 4/10
    2021
    observational
    n=100

    Alkhatatbeh MJ

    Sleep bruxism was associated with vitamin D deficiency and low consumption of calcium and was also associated with increased scores of anxiety and depression.

    View source

    Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis

    Score: 8/10
    2010
    meta_analysis
    n=11921

    Bolland MJ, Avenell A, Baron JA +4 more

    Calcium supplements without co-administered vitamin D were associated with an approximately 30% increased risk of myocardial infarction in pooled patient-level analysis.

    View source

    Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk for kidney stones in women

    Score: 8/10
    1997
    cohort
    n=91731

    Curhan GC, et al.

    High intake of dietary calcium appears to decrease risk for symptomatic kidney stones, whereas intake of supplemental calcium may increase risk.

    View source

    Effect of nutritional interventions on the psychological symptoms of premenstrual syndrome in women of reproductive age: a systematic review of randomized controlled trials

    Score: 8/10
    2025
    systematic_review

    Robinson J, Ferreira A, Iacovou M +1 more

    To date, high-quality research investigating the effects of dietary and nutrient intervention on PMS is limited.

    View source

    Beneficial Role of Calcium in Premenstrual Syndrome: A Systematic Review of Current Literature

    Score: 7/10
    2020
    meta_analysis

    Arab A, Rafie N, Askari G +1 more

    Calcium 1000-1200 mg daily significantly reduced total premenstrual symptom scores

    View source

    Safety Information

    Potential Side Effects

    Generally safe when not exceeding 2500mg daily. High doses may cause kidney stones or constipation

    Contraindications

    Hypercalcaemia, primary hyperparathyroidism, sarcoidosis, and severe renal impairment. Caution with a history of calcium oxalate stones — dietary calcium with meals is protective, but supplements taken away from food are not.

    Drug Interactions

    • Levothyroxine — reduced absorption, separate by 4 hours
    • Tetracycline and fluoroquinolone antibiotics — chelation, separate by 2-4 hours
    • Bisphosphonates — separate by at least 30-60 minutes
    • Iron and zinc — competitive absorption, take at different times
    • Thiazide diuretics — raise calcium retention, risk of hypercalcaemia
    • Levodopa — reduced absorption

    Pregnancy & Breastfeeding

    Pregnancy: Considered safe

    Breastfeeding: Considered safe

    Dosage Guidelines

    Dosage Used in Studies

    500-1200 mg

    Best Time to Take

    Split morning and evening; never more than 500 mg at once

    Best Form

    Calcium citrate in split doses of 500 mg or less, taken with vitamin D

    Bioavailability

    Fractional absorption is around 35% at 300 mg and falls sharply as dose rises. Vitamin D status, gastric acid, and oxalate or phytate in the same meal all affect uptake.

    Dosing by Goal

    GoalDoseNotes
    GeneralAim for 1000 mg/day total intake (1200 mg for women over 50 and adults over 70), diet first
    PMS1000-1200 mg/day in divided doses
    Pregnancy1.5-2 g/day where dietary intake is low, for pre-eclampsia prevention
    Supplement gapSupplement only the shortfall, typically 500 mg/day
    Upper limit2000-2500 mg/day total from all sources
    Per-dose limit500 mg or less per dose — absorption efficiency collapses above this
    NotesTake carbonate with food; citrate any time. Pair with vitamin D 800-2000 IU and consider vitamin K2.

    Forms Compared

    Calcium citrate

    21% elemental; absorbed without stomach acid, best on PPIs or after bariatric surgery

    Calcium carbonate

    40% elemental and cheapest, but needs food and gastric acid; more constipating

    Calcium citrate malate

    Good absorption, used in several fortification trials

    Microcrystalline hydroxyapatite

    Bone-derived, includes phosphorus and matrix proteins; modest evidence

    Algae-derived (AlgaeCal)

    Provides trace minerals; expensive relative to the added benefit

    Food & Timing

    Carbonate with meals; citrate with or without food. Separate from iron, zinc, thyroid medication and levodopa by at least two hours.

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.