Supplement analysis backed by scientific evidence · PT

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Limited evidenceVitamins & minerals

Algae Calcium

Plant-sourced calcium from red marine algae (Lithothamnion, sold as Aquamin and similar), marketed as more absorbable and better for bone than calcium carbonate. The human evidence is one 12-person single-dose study of metabolic markers — no fracture trial, no bone density superiority trial, and a price several times that of carbonate.

What the science says

  • Human evidence is a single 12-person pilot on surrogate markers Limited evidence

    A double-blind crossover pilot gave 12 fasting premenopausal women one dose of algae-derived calcium, calcium carbonate, or placebo. The algal calcium produced greater 12-hour urinary calcium clearance than placebo (p=0.004) and more prolonged PTH suppression after a meal, with carbonate falling in between and not differing significantly from placebo on clearance. That is a single acute dose, n=12, measuring biochemistry — it is not evidence about bones.

  • No clinical bone outcome data Limited evidence

    The supporting literature for marine multi-mineral calcium is dominated by cell culture and ovariectomised rat models showing enhanced osteoblast mineralisation and preserved bone structure. No randomised controlled trial has shown algae calcium produces greater bone mineral density gains or fewer fractures than ordinary calcium carbonate in humans.

  • The underlying calcium effect it is competing on is small anyway Strong evidence

    Meta-analysis shows increasing calcium intake raises bone mineral density by roughly 1-2% without further accumulation, and a companion systematic review found the fracture-prevention evidence weak and inconsistent. Paying a large premium to optimise a form of calcium is optimising a small effect.

Dosage & safety

Studied doseProducts typically supply 720-1,000 mg elemental calcium per day, usually combined with vitamin D3, vitamin K2, magnesium and trace minerals — which makes attributing any effect to the algal calcium itself impossible. The pilot study used a single dose in the region of 1,000 mg elemental calcium. General calcium guidance applies: 500-600 mg elemental per serving, 1,000-1,200 mg/day total from diet plus supplement.
SafetyAs a marine-sourced mineral, third-party heavy metal testing matters — lead is detectable across mineral supplement categories generally. Standard calcium risks otherwise: constipation and bloating, hypercalcaemia at excessive intakes, do not exceed 2,000-2,500 mg/day total calcium. Separate by 2-4 hours from levothyroxine, iron, tetracyclines, quinolones and bisphosphonates. Avoid without medical advice in hypercalcaemia, primary hyperparathyroidism or a history of calcium kidney stones. Not banned in sport.

Scientific references

Where to buy

NOW Foods, Red Mineral Algae, 180 Veg Capsules

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