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Marine Based Cal-Mag 500/250 mg

4.7
★ ★ ★ ★ ★
(666 ratings)
Calcium 500 mg
Magnesium 250 mg
Product Image
Score71
Meaningful marine-sourced minerals are the draw, while magnesium hydroxide, four capsules, and high cost limit broader value.
How scoring works
Capsule
Quantity:120 Capsule(s) • (30 servings)
Goals:
Bone Health
General Health
Energy

Score 71

Meaningful marine-sourced minerals are the draw, while magnesium hydroxide, four capsules, and high cost limit broader value.
How scoring works
$27.74($0.92 per serving)
Vitacost
$ 28.53
iHerb
$ 27.74
Pure Formulas
$ 28.27
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Analysis

Aquamin red-algae calcium supplies 500 mg, while seawater-derived magnesium provides 250 mg. The marine sources offer a distinct alternative to conventional rock-derived mineral salts.

Magnesium hydroxide is part of the magnesium form and can have a laxative effect. Inactive ingredients and detailed intake directions are not supplied, limiting a full label assessment.

Four capsules per serving are a meaningful burden, and serving value is weak. The formula best fits users who specifically prefer marine mineral sources rather than those seeking the lowest-cost calcium and magnesium.

Who is it for
  • Adults who prefer marine-derived minerals
  • People seeking moderate calcium and magnesium amounts
Best for
  • Aquamin calcium supplementation
  • Marine-sourced bone-mineral support

Pros

  • Uses red-algae and seawater mineral sources
  • Provides meaningful calcium and magnesium amounts
  • Coherent, focused formula

Cons

  • Includes magnesium hydroxide
  • Requires four capsules
  • High serving cost

Warnings

  • Magnesium hydroxide may cause loose stools or abdominal cramping
  • Separate calcium from thyroid hormone, bisphosphonates, and certain antibiotics
  • People with impaired kidney function should review supplemental magnesium use with a clinician

Nutrient quality

87 Highest impact

Aquamin red-algae calcium is a useful marine source, while magnesium hydroxide has limited absorption potential, and the 500 mg calcium and 250 mg magnesium amounts fit practical supplemental ranges. The disclosed amounts show no obvious broad overdosing for typical supplemental use, while marine calcium and magnesium form a coherent mineral-support combination.

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Ingredient transparency

70 High impact

Total mineral amounts are shown, but repeated amounts across forms make each form contribution unclear, and no proprietary blend hides the amount of a listed core mineral. Serving count is supplied, but complete daily-use directions are not provided, while inactive ingredients and excipients are not included in the supplied label details.

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Customer satisfaction

72 High impact

The supplied average rating is strong, and moderate review volume provides a reasonable evidence base. Specific review themes are unavailable, so repeated negatives and real-world fit remain uncertain.

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Value for money

53 Moderate impact

Mixed mineral forms and dosing trade-offs weaken formula value, and the very high serving cost substantially weakens value. The small sodium amount is incidental and does not materially dilute the mineral formula, while form, dose, or serving-value limitations make it less competitive than similar products.

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Goals

Bone Health
Bone Health
Impact
Highest effect
A Goal FitA Strength of SupportB+ CoverageA- Formula Quality
Magnesium · 250 mgCalcium · 500 mg

Marine calcium and magnesium provide substantial structural minerals in well-regarded Aquamin sources. Both nutrients have established roles in maintaining bone tissue.

The mineral pairing is focused and more complete than a calcium-only formula. It does not include vitamin D, vitamin K, or a protein-matrix ingredient to support mineral transport and broader skeletal needs.

Study evidence
Calcium Supportive 144 studies
Magnesium Supportive 48 studies
General Health
Stress Resilience
General Health
Impact
High effect
A- Goal FitC+ Strength of SupportC- CoverageB Formula Quality
Magnesium · 250 mg

Magnesium and calcium support foundational muscle, nerve, and bone functions. The combination is relevant to daily health, but the magnesium form limits how much systemic support the serving may provide.

The 250 mg magnesium amount is appropriate for routine supplementation and is clearly disclosed. Magnesium hydroxide has low absorption, and the formula lacks vitamin D or other cofactors that could make the mineral pairing more complete.

Study evidence
Magnesium Supportive 114 studies
Energy
Energy
Impact
High effect
B Goal FitB- Strength of SupportC- CoverageB- Formula Quality
Magnesium · 250 mg

Magnesium reaches a meaningful amount for ATP-related enzyme activity and muscle function. The elemental amount is clearly disclosed.

Magnesium hydroxide has limited systemic absorption and a large calcium amount may compete with magnesium uptake. The four-capsule bone-mineral formula offers little support for alertness or stress resilience.

Study evidence
Magnesium Supportive 4 studies
Heart Health
Healthy Blood Pressure
Heart Health
Impact
Moderate effect
C Goal FitB- Strength of SupportD CoverageC+ Formula Quality
Magnesium · 250 mg

A meaningful magnesium amount supports normal rhythm and vascular function, but hydroxide has limited absorption. Calcium dominates the mineral balance and the formula lacks more targeted heart actives.

The disclosed serving supports one established mineral pathway rather than broad cardiovascular coverage. Four capsules and basic mineral forms reduce its practical appeal.

Study evidence
Magnesium Supportive 158 studies
Stress Relief
Stress Relief
Impact
Moderate effect
C Goal FitC Strength of SupportD- CoverageB Formula Quality
Magnesium · 250 mg

Magnesium supports nervous-system regulation and muscle relaxation, with the clearest benefit when intake is inadequate. Its physiological role is established, while human evidence for reducing perceived stress in otherwise replete users is less robust than for targeted adaptogens or theanine.

The 250 mg elemental magnesium amount meets a useful supplemental range. Magnesium hydroxide has low systemic absorption despite a clear amount and marine source.

Study evidence
Magnesium Supportive 13 studies
Digestive Health
Digestive Health
Impact
Moderate effect
C Goal FitB- Strength of SupportD- CoverageC Formula Quality
Magnesium · 250 mg

Magnesium hydroxide can support stool softening, while the larger calcium amount may promote constipation in some users. The formula is a calcium-magnesium supplement rather than a dedicated digestive product.

The 250 mg magnesium amount is visible, but hydroxide has low systemic absorption and can produce loose stools. Calcium may reduce the net motility effect, making individual response less predictable.

Study evidence
Magnesium Supportive 50 studies
Cardiovascular Support
Cardiovascular Support
Impact
Moderate effect
C- Goal FitC- Strength of SupportF CoverageC+ Formula Quality
Magnesium · 250 mg

Magnesium provides direct support for vascular tone and normal cardiac electrical activity. Human evidence is relevant, but the product does not address lipid management, nitric oxide production, or cardiac energy.

The magnesium amount is practical, but hydroxide has low systemic absorption and four capsules create a larger serving burden. Twice as much calcium shifts the formula toward bone support rather than cardiovascular use.

Study evidence
Magnesium Supportive 123 studies

Ingredients

IngredientAmount per serving
Calcium (Aquamin Red Algae, Seawater)
 500 mg
Magnesium (Aquamin Seawater, Magnesium Hydroxide)
 250 mg
Sodium
15 mg
Gluten Free Adults 18–50 Vegan Vegetarian
Report overview
Calcium (Aquamin Red Algae, Seawater) · 500 mg OverallScore84
A+ Active Ingredient Quality & BioavailabilityA+ Dose, Safety & Label TransparencyF Value

Red-algae Aquamin provides a well-regarded marine calcium source with strong absorption potential. The serving gives a practical calcium amount and includes magnesium as a complementary mineral. The premium form comes at a high cost per serving, creating a clear value trade-off.

View ingredientView products
Magnesium (Aquamin Seawater, Magnesium Hydroxide) · 250 mg OverallScore42
F Active Ingredient Quality & BioavailabilityB+ Dose, Safety & Label TransparencyF Value

The elemental magnesium amount is clear and suitable for routine supplementation, but hydroxide has low absorption potential. Calcium is present at exactly twice the magnesium amount without a listed vitamin D, boron, or vitamin B6 cofactor. The high serving cost offers poor value for these basic mineral forms.

View ingredientView products
Loading alternative details
94 Performance

Cal/Mag 500 mg/250 mg

NaturesPlus
<p>Chelated calcium and magnesium provide a balanced, focused mineral formula with stronger form quality than products relying heavily on carbonate or oxide. The simple serving is easy to assess, though vitamin D and vitamin K are not included.</p>
92 Performance

Magnesium Bisglycinate Chelate

Healthy Origins
<p>TRAACS magnesium bisglycinate provides a well-absorbed form at a useful amount and avoids the weaker oxide forms found in many combinations. The powder covers magnesium only, so a separate calcium source is needed when both minerals are intended.</p>
92 Performance

Calcium Citrate Pure Powder

NOW
<p>Calcium citrate provides a well-absorbed, clearly disclosed calcium source in an adjustable powder. The focused formula omits magnesium, vitamin D, and vitamin K, so it works better as a targeted calcium option than as a complete replacement.</p>
87 Budget

600 Calcium Supplement

21st Century
<p>A straightforward calcium carbonate tablet provides a much lower-cost source of calcium at a practical supplemental amount. Carbonate works best with food, and the formula omits magnesium, vitamin D, and other bone-supporting cofactors found in broader products.</p>
86 Budget

Calcium Carbonate

NOW
<p>A pure calcium carbonate powder offers substantial calcium with excellent serving value and no unrelated actives. Food and stomach acid aid carbonate absorption, while the calcium-only design leaves magnesium and vitamin D uncovered.</p>
85 Budget

Calcium 600 with Vitamin D3

Nature's Bounty
<p>Calcium with vitamin D3 provides an economical, meaningfully dosed bone-support pairing. Calcium carbonate is best taken with food, and the formula does not replace the original magnesium coverage.</p>
94 Value

Krebs Magnesium Potassium Complex

Nature's Way
<p>Magnesium lysinate and malate provide favorable forms at a useful amount, with modest potassium adding complementary mineral support. Serving value is strong, but the formula requires a separate calcium source when calcium is also needed.</p>
90 Value

Calcium Citrate +D3 Petites

21st Century
<p>Calcium citrate with vitamin D3 combines a practical amount, favorable absorption, and accessible serving value. The focused formula does not provide magnesium, and missing excipient details modestly limit transparency.</p>
88 Value

Albion Chelated Calcium 180 mg

Swanson Ultra
<p>Calcium glycinate chelate with a small vitamin D3 addition offers a useful balance of form quality and value. The supplied product name and serving amount conflict, so the current label should be checked, and magnesium still needs separate coverage.</p>
Report alternatives

Sources

Published studies used for the product analysis and the top-ranked studies for each ingredient and goal.

  1. What is the impact of daily oral supplementation of vitamin D3 (cholecalciferol) plus calcium on the incidence of hip fracture in older people? A systematic review and meta-analysis.
    Manoj P; Derwin R; George S · International journal of older people nursing · 2023
    Meta-analysis12,620 participants7 studies pooledBone Health forCalcium
  2. Calcium supplementation prevents seasonal bone loss and changes in biochemical markers of bone turnover in elderly New England women: a randomized placebo-controlled trial.
    Storm D; Eslin R; Porter ES; Musgrave K; Vereault D; Patton C; Kessenich C; Mohan S; Chen T; Holick MF; Rosen CJ · The Journal of clinical endocrinology and metabolism · 1998
    Randomized trial60 participantsBone Health forCalcium
  3. The effects of calcium supplementation (milk powder or tablets) and exercise on bone density in postmenopausal women.
    Prince R; Devine A; Dick I; Criddle A; Kerr D; Kent N; Price R; Randell A · Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research · 1995
    Randomized trial168 participantsBone Health forCalcium
  4. The efficacy of calcium supplementation alone in elderly Thai women over a 2-year period: a randomized controlled trial.
    Rajatanavin R; Chailurkit L; Saetung S; Thakkinstian A; Nimitphong H · Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA · 2014
    Randomized trial404 participantsBone Health forCalcium
  5. Calcium-enriched foods and bone mass growth in prepubertal girls: a randomized, double-blind, placebo-controlled trial.
    Bonjour JP; Carrie AL; Ferrari S; Clavien H; Slosman D; Theintz G; Rizzoli R · The Journal of clinical investigation · 1997
    Randomized trial149 participantsBone Health forCalcium
  6. Association between Serum Magnesium and Fractures: A Systematic Review and Meta-Analysis of Observational Studies.
    Dominguez LJ; Veronese N; Ciriminna S; Pérez-Albela JL; Vásquez-López VF; Rodas-Regalado S; Di Bella G; Parisi A; Tagliaferri F; Barbagallo M · Nutrients · 2023
    Meta-analysis119,755 participants4 studies pooledBone Health forMagnesium
  7. Bioabsorbable Magnesium-Based Materials Potential and Safety in Bone Surgery: A Systematic Review.
    Hung CH; Kwok YC; Yip J; Wong HH; Leung YY · Craniomaxillofacial trauma & reconstruction · 2025
    Systematic review386 participants8 studies pooledBone Health forMagnesium
  8. Vascularized bone grafting fixed by biodegradable magnesium screw for treating osteonecrosis of the femoral head.
    Zhao D; Huang S; Lu F; Wang B; Yang L; Qin L; Yang K; Li Y; Li W; Wang W; Tian S; Zhang X; Gao W; Wang Z; Zhang Y; Xie X; Wang J; Li J · Biomaterials · 2016
    Randomized trial48 participantsBone Health forMagnesium
  9. An update on magnesium and bone health.
    Rondanelli M; Faliva MA; Tartara A; Gasparri C; Perna S; Infantino V; Riva A; Petrangolini G; Peroni G · Biometals : an international journal on the role of metal ions in biology, biochemistry, and medicine · 2022
    Narrative reviewBone Health forMagnesium
  10. Sex-specific differences in the association of magnesium intake with femoral neck bone mineral density among older adults.
    Wang B; Tan X; Yao X; Zhu Z · Endocrine connections · 2025
    Cross-sectional study1,343 participantsBone Health forMagnesium
  11. Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies.
    Del Gobbo LC; Imamura F; Wu JH; de Oliveira Otto MC; Chiuve SE; Mozaffarian D · The American journal of clinical nutrition · 2013
    Meta-analysis313,041 participants16 studies pooledCardiovascular Support forMagnesium
  12. Magnesium and the risk of cardiovascular events: a meta-analysis of prospective cohort studies.
    Qu X; Jin F; Hao Y; Li H; Tang T; Wang H; Yan W; Dai K · PloS one · 2013
    Meta-analysis532,979 participants19 studies pooledCardiovascular Support forMagnesium
  13. Quantitative Association Between Serum/Dietary Magnesium and Cardiovascular Disease/Coronary Heart Disease Risk: A Dose-Response Meta-analysis of Prospective Cohort Studies.
    Zhao L; Hu M; Yang L; Xu H; Song W; Qian Y; Zhao M · Journal of cardiovascular pharmacology · 2020
    Meta-analysis544,581 participants18 studies pooledCardiovascular Support Heart Health forMagnesium
  14. Comparative Efficacy of Nutraceuticals on Endothelial Function: A Systematic Review and Network Meta-Analysis.
    Norouzzadeh M; Rashedi MH; Mahdavi-Mazdeh G; Kosari A; Shahinfar H · Current atherosclerosis reports · 2026
    Meta-analysisCardiovascular Support Heart Health forMagnesium
  15. Serum magnesium, mortality, and cardiovascular disease in chronic kidney disease and end-stage renal disease patients: a systematic review and meta-analysis.
    Xiong J; He T; Wang M; Nie L; Zhang Y; Wang Y; Huang Y; Feng B; Zhang J; Zhao J · Journal of nephrology · 2020
    Meta-analysis200,934 participants20 studies pooledCardiovascular Support forMagnesium
  16. Efficacy of oral magnesium therapy in the treatment of chronic constipation in spastic cerebral palsy children: a randomized controlled trial.
    Hassanein SMA; Deifallah SM; Bastawy HA · World journal of pediatrics : WJP · 2021
    Randomized trial100 participantsDigestive Health forMagnesium
  17. Ca:Mg ratio, medium-chain fatty acids, and the gut microbiome.
    Fan L; Zhu X; Sun S; Yu C; Huang X; Ness R; Dugan LL; Shu L; Seidner DL; Murff HJ; Fodor AA; Azcarate-Peril MA; Shrubsole MJ; Dai Q · Clinical nutrition (Edinburgh, Scotland) · 2022
    Randomized trial240 participantsDigestive Health forMagnesium
  18. The Magnesium-Rich Formula for Functional Constipation in Infants: a Randomized Comparator-Controlled Study.
    Benninga MA; MENA Infant Constipation Study Group; Vandenplas Y · Pediatric gastroenterology, hepatology & nutrition · 2022
    Randomized trial286 participantsDigestive Health forMagnesium
  19. A Randomized Double-blind Placebo-controlled Trial on the Effect of Magnesium Oxide in Patients With Chronic Constipation.
    Mori S; Tomita T; Fujimura K; Asano H; Ogawa T; Yamasaki T; Kondo T; Kono T; Tozawa K; Oshima T; Fukui H; Kimura T; Watari J; Miwa H · Journal of neurogastroenterology and motility · 2022
    Randomized trial34 participantsDigestive Health forMagnesium
  20. Magnesium treatment increases gut microbiome synthesizing vitamin D and inhibiting colorectal cancer: results from a double-blind precision-based randomized placebo-controlled trial.
    Sun E; Zhu X; Ness RM; Murff HJ; Sun S; Yu C; Fan L; Azcarate-Peril MA; Shrubsole MJ; Dai Q · The American journal of clinical nutrition · 2025
    Randomized trial240 participantsDigestive Health forMagnesium
  21. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial.
    Hausenblas HA; Lynch T; Hooper S; Shrestha A; Rosendale D; Gu J · Sleep medicine: X · 2025
    Randomized trial80 participantsEnergy forMagnesium
  22. Total magnesium intake and risk of frailty in older women.
    Struijk EA; Fung TT; Bischoff-Ferrari HA; Willett WC; Lopez-Garcia E · Journal of cachexia, sarcopenia and muscle · 2024
    Cohort study81,524 participantsEnergy forMagnesium
  23. Red blood cell magnesium and chronic fatigue syndrome.
    Cox IM; Campbell MJ; Dowson D · Lancet (London, England) · 1991
    Randomized trial32 participantsEnergy forMagnesium
  24. Exercise, magnesium and immune function.
    Laires MJ; Monteiro C · Magnesium research · 2008
    Narrative reviewEnergy forMagnesium
  25. Perioperative systemic magnesium to minimize postoperative pain: a meta-analysis of randomized controlled trials.
    De Oliveira GS; Castro-Alves LJ; Khan JH; McCarthy RJ · Anesthesiology · 2013
    Meta-analysis1,257 participants20 studies pooledGeneral Health forMagnesium
  26. Long-term outcome after intravenous magnesium sulphate in suspected acute myocardial infarction: the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2).
    Woods KL; Fletcher S · Lancet (London, England) · 1994
    Randomized trial2,316 participantsGeneral Health forMagnesium
  27. Association of magnesium sulfate use with mortality in critically ill patients with sepsis: a retrospective propensity score-matched cohort study.
    Gu WJ; Duan XJ; Liu XZ; Cen Y; Tao LY; Lyu J; Yin HY · British journal of anaesthesia · 2023
    Cohort study10,999 participantsGeneral Health forMagnesium
  28. Hypomagnesemia and Mortality in Incident Hemodialysis Patients.
    Li L; Streja E; Rhee CM; Mehrotra R; Soohoo M; Brunelli SM; Kovesdy CP; Kalantar-Zadeh K · American journal of kidney diseases : the official journal of the National Kidney Foundation · 2016
    Cohort study9,359 participantsGeneral Health forMagnesium
  29. The effects of magnesium supplementation on abnormal uterine bleeding, alopecia, quality of life, and acne in women with polycystic ovary syndrome: a randomized clinical trial.
    Jaripur M; Ghasemi-Tehrani H; Askari G; Gholizadeh-Moghaddam M; Clark CCT; Rouhani MH · Reproductive biology and endocrinology : RB&E · 2022
    Randomized trial64 participantsGeneral Health forMagnesium
  30. Effects of magnesium supplementation on improving hyperglycemia, hypercholesterolemia, and hypertension in type 2 diabetes: A pooled analysis of 24 randomized controlled trials.
    Xu L; Li X; Wang X; Xu M · Frontiers in nutrition · 2023
    Meta-analysis1,325 participants24 studies pooledHeart Health forMagnesium
  31. The effect of lowering blood pressure by magnesium supplementation in diabetic hypertensive adults with low serum magnesium levels: a randomized, double-blind, placebo-controlled clinical trial.
    Guerrero-Romero F; Rodríguez-Morán M · Journal of human hypertension · 2009
    Randomized trial82 participantsHeart Health forMagnesium
  32. Positive effects of magnesium supplementation in metabolic syndrome.
    Kisters S; Kisters K; Werner T; Vormann J; Tokmak F; Westhoff T; Gröber U; Predel HG; Reuter H · International journal of clinical pharmacology and therapeutics · 2024
    Randomized trial54 participantsHeart Health forMagnesium
  33. Role of magnesium supplementation in the treatment of depression: A randomized clinical trial.
    Tarleton EK; Littenberg B; MacLean CD; Kennedy AG; Daley C · PloS one · 2017
    Randomized trial126 participantsStress Relief forMagnesium
  34. Effects of Intravenous Esketamine or Magnesium Sulfate on Early Postoperative Negative Emotions and Pain in Patients Undergoing Endoscopic Sinus Surgery: A Randomized Controlled Trial.
    Wang L; Zhou J; Liu Q; Qian K; Wang L; Xie C · Therapeutics and clinical risk management · 2026
    Randomized trial137 participantsStress Relief forMagnesium
  35. Effect of short-term magnesium supplementation on anxiety, depression and sleep quality in patients after open-heart surgery.
    Saba S; Faizi F; Sepandi M; Nehrir B · Magnesium research · 2022
    Non-randomized trial60 participantsStress Relief forMagnesium
  36. Effects of dry needling compared to magnesium infiltration in trigger points for patients with myofascial pain syndrome: a randomized controlled study in Tunisia.
    Dhouibi J; Moncer R; Kalbousi N; Gaddour M; Laayouni S; Ouanes W; Kacem B; Jemni S · Korean journal of family medicine · 2026
    Randomized trial45 participantsStress Relief forMagnesium
  37. Effect of magnesium and vitamin B6 supplementation on mental health and quality of life in stressed healthy adults: Post-hoc analysis of a randomised controlled trial.
    Noah L; Dye L; Bois De Fer B; Mazur A; Pickering G; Pouteau E · Stress and health : journal of the International Society for the Investigation of Stress · 2021
    Randomized trialStress Relief forMagnesium