Lithothamnion (Aquamin)
Also called Aquamin, Aquamin F, red mineral algae, red algae calcium, seaweed-derived calcium, Lithothamnion calcareum.
Best grade C across 8 graded outcomes Mineral Last checked
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The short answer
From 10 sourcesAquamin, the main Lithothamnion ingredient, is a calcium source. In a 24-month trial of 300 postmenopausal women it did not change bone density, though bone-turnover markers and LDL cholesterol fell versus control. Knee-arthritis and colon studies are small pilots, several funded by the maker. Calcium upper limits apply.
Every graded outcome on this page
8 rows · line = participants- CGrade CBlood lipids in postmenopausal womenCholesteroln 300
- DGrade DKnee osteoarthritis pain and walking distanceJointsn 70
- DGrade DColon bacteria and stool metabolitesGutn 30
- DGrade DKnee osteoarthritis during NSAID reductionJointsn 29
- DGrade DInflammation and bone markers in ulcerative colitis in remission or mildGutn 28
- DGrade DGut permeability in ulcerative colitisGutn 16
- DGrade DCalcium metabolism markers after a single doseCalcium handlingn 12
- ∅No effectBone mineral density in postmenopausal womenBone densityn 300
- 5 more graded outcomes, in the evidence chapter
Key facts
What it is
Lithothamnion is a red marine alga; its mineral powder, sold as Aquamin, is rich in calcium and magnesium with trace elements.
Forms
Form
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Aquamin / Aquamin F powder or capsules | Varies3Trials report about 800 mg calcium per 2.4 g Aquamin; elemental content varies by product label | After one dose, urinary calcium clearance rose and parathyroid hormone stayed lower after a meal than with placebo.6 | Well tolerated in knee trials, with adverse events similar to placebo; no change in liver or kidney markers over 90 days. A combined Aquamin-Mg/Aquamin F supplement caused no significant adverse events over 12 weeks in a small group of older adults.45710 | Bone density, cholesterol, knee osteoarthritis, colon markers |
What the human research says
Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.
Trial map
8 graded outcomes, largest study first8 graded outcomes: 3 improved, 4 mixed, 1 no effect. The largest, a 2016 randomized trial of 300 people on blood lipids in postmenopausal women, found an improvement.
1Blood lipids in postmenopausal women
Improved · Grade C · RCT, 300 people, 2016
Postmenopausal women in the same 24-month trial
Dose, result and source| Outcome | Found | People | Study | Who was studied |
|---|---|---|---|---|
| Blood lipids in postmenopausal women | Improved | 300 | Grade C · RCT, 2016 | Postmenopausal women in the same 24-month trial |
| Bone mineral density in postmenopausal women | No effect | 300 | No-effect grade · RCT, 2014 | Non-osteoporotic postmenopausal women in Northern Ireland |
| Knee osteoarthritis pain and walking distance | Mixed | 70 | Grade D · RCT, 2008 | Adults with moderate to severe knee osteoarthritis (50 completed) |
| Colon bacteria and stool metabolites | Mixed | 30 | Grade D · RCT, 2020 | Healthy adults (Aquamin, calcium alone or placebo) |
| Knee osteoarthritis during NSAID reduction | Mixed | 29 | Grade D · RCT, 2009 | Adults with moderate to severe knee osteoarthritis (22 treated, 14 completed) |
| Inflammation and bone markers in ulcerative colitis in remission or mild | Improved | 28 | Grade D · RCT, 2025 | Adults with ulcerative colitis in remission or with mild disease |
| Gut permeability in ulcerative colitis | Improved | 16 | Grade D · Open-label trial, 2026 | People with mild or inactive ulcerative colitis and healthy controls (8 per group) |
| Calcium metabolism markers after a single dose | Mixed | 12 | Grade D · Crossover RCT, 2018 | Fasting premenopausal women |
Every graded row
8 rowsShowing 8 of 8 outcomes. Human trials only.
CGrade CBlood lipids in postmenopausal womenCholesterolLower LDL vs controlRCT
n 300 · 2016
Improved LDL and total cholesterol were lower than control after 24 months in both calcium groups; HDL, triglycerides, blood pressure, body composition and cytokines did not change.
- Design
- RCT, n = 300, 2016
- Population
- Postmenopausal women in the same 24-month trial
- Form
- Aquamin, alone or with short-chain fructo-oligosaccharides
- Dose
- 2.4 g Aquamin (800 mg calcium) a day
- Duration
- 24 months
- Source
- Reference 3 · PubMed 26669430 (opens PubMed)
DGrade DKnee osteoarthritis pain and walking distanceJointsMixed; baseline imbalanceRCT
n 70 · 2008
Mixed Pain score changes differed between groups (p = 0.009), but groups differed at baseline. Within the Aquamin group pain and stiffness improved and walking distance rose by 101 feet (7%); the Aquamin plus glucosamine group did not improve.
- Design
- RCT, n = 70, 2008
- Population
- Adults with moderate to severe knee osteoarthritis (50 completed)
- Form
- Aquamin, glucosamine, both, or placebo
- Dose
- 2,400 mg Aquamin a day
- Duration
- 12 weeks
- Source
- Reference 4 · PubMed 18279523 (opens PubMed)
DGrade DColon bacteria and stool metabolitesGutShifted gut bacteriaRCT
n 30 · 2020
Mixed Total bacterial DNA in colon biopsies fell (P = 0.0001) and stool bile acids fell (P = 0.0375) with Aquamin; acetate rose slightly. Liver and kidney markers did not change.
- Design
- RCT, n = 30, 2020
- Population
- Healthy adults (Aquamin, calcium alone or placebo)
- Form
- Aquamin
- Dose
- Amount delivering 800 mg calcium a day
- Duration
- 90 days
- Source
- Reference 7 · PubMed 31771942 (opens PubMed)
DGrade DKnee osteoarthritis during NSAID reductionJointsMixedRCT
n 29 · 2009
Mixed WOMAC scores did not differ from placebo; knee range of motion and 6-minute walking distance (difference 136 feet) improved vs placebo during a 50% cut in NSAID use.
- Design
- RCT, n = 29, 2009
- Population
- Adults with moderate to severe knee osteoarthritis (22 treated, 14 completed)
- Form
- Aquamin F
- Dose
- 2,400 mg a day
- Duration
- Up to 12 weeks
- Source
- Reference 5 · PubMed 19187557 (opens PubMed)
DGrade DInflammation and bone markers in ulcerative colitis in remission or mildGutBetter inflammation markersRCT
n 28 · 2025
Improved Combined inflammation-marker differences fell 24% with Aquamin vs a 38% rise on placebo (p = 0.0284); hip strength index rose 7.3% after 180 days.
- Design
- RCT, n = 28, 2025
- Population
- Adults with ulcerative colitis in remission or with mild disease
- Form
- Aquamin
- Dose
- Daily capsules (amount not stated in the abstract)
- Duration
- 180 days (placebo arm switched to Aquamin at day 90)
- Source
- Reference 8 · PubMed 41359652 (opens PubMed)
DGrade DGut permeability in ulcerative colitisGutLower permeability markerOpen-label trial
n 16 · 2026
Improved In ulcerative colitis, total urinary mannitol excretion (a permeability marker) fell 29% after 90 days (p = 0.024); no serious adverse events.
- Design
- Open-label trial, n = 16, 2026
- Population
- People with mild or inactive ulcerative colitis and healthy controls (8 per group)
- Form
- Aquamin capsules
- Dose
- 800 mg calcium a day
- Duration
- 90 days
- Source
- Reference 9 · PubMed 42440705 (opens PubMed)
DGrade DCalcium metabolism markers after a single doseCalcium handlingDifferent calcium markersCrossover RCT
n 12 · 2018
Mixed Urinary calcium clearance at 12 hours was greater than placebo (P = .004) and parathyroid hormone stayed lower after a meal; calcium carbonate gave an intermediate response.
- Design
- Crossover RCT, n = 12, 2018
- Population
- Fasting premenopausal women
- Form
- Aquamin F vs calcium carbonate vs placebo
- Dose
- Single dose (amount not stated in the abstract)
- Duration
- 12 hours per test
- Source
- Reference 6 · PubMed 29023178 (opens PubMed)
∅No effectBone mineral density in postmenopausal womenBone densityNo change in bone densityRCT
n 300 · 2014
No effect Change in bone mineral density did not differ from the maltodextrin control; bone-turnover markers (osteocalcin, CTX) fell more with calcium at 12 months.
- Design
- RCT, n = 300, 2014
- Population
- Non-osteoporotic postmenopausal women in Northern Ireland
- Form
- Marine-derived calcium-rich multi-mineral (Aquamin), alone or with short-chain fructo-oligosaccharides
- Dose
- 800 mg calcium a day
- Duration
- 24 months
- Source
- Reference 2 · PubMed 24453130 (opens PubMed)
What the numbers add up to
Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.
Calcium, not a bone builder
The largest trial found no change in bone density over 24 months, the same outcome many calcium trials report; only turnover markers moved.2
Joint evidence is maker-funded and tiny
Studied doses
Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.
Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.
Doses studied in human trials
Interactions and safety
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
What Lithothamnion meets
4 cited rows 3 tested togetherMedicines 4
Supplements and foods 2
- Drug label or FDA notice
- Reference summary
- Tested together in a graded trial
Choose a medicine or supplement above to read its cited rows here.
Also cited: 3 tested together
Dolutegravir
Drug labelDrug label or FDA notice
Dolutegravir, for example Tivicay, Dovato: Calcium can substantially lower dolutegravir blood levels (chelation). The FDA labels advise dolutegravir 2 hours before or 6 hours after calcium supplements.
Source 1, NIH Office of Dietary Supplements (2026)
Levothyroxine
Drug labelDrug label or FDA notice
Levothyroxine: Calcium carbonate can reduce levothyroxine absorption; the FDA label says to avoid taking them within 4 hours of each other.
Source 1, NIH Office of Dietary Supplements (2026)
Lithium
NIH fact sheetReference summary
Lithium: Long-term lithium can raise blood calcium, and adding calcium supplements could increase this risk.
Source 1, NIH Office of Dietary Supplements (2026)
Quinolone antibiotics
NIH fact sheetReference summary
Quinolone antibiotics, for example ciprofloxacin, gemifloxacin, moxifloxacin: Taken together, calcium reduces quinolone absorption; ODS reports separating them by 2 hours prevents this.
Source 1, NIH Office of Dietary Supplements (2026)
GlucosamineGlucosamine page
Tested together
Knee osteoarthritis pain and walking distance. Graded on the Lithothamnion page; tested together is not a claim that they work better together.
InulinInulin page
Tested together
Bone mineral density in postmenopausal women. Graded on the Lithothamnion page; tested together is not a claim that they work better together.
Tested together
Blood lipids in postmenopausal women. Graded on the Lithothamnion page; tested together is not a claim that they work better together.
Interactions
4 agents| Agent | What the source says | Evidence |
|---|---|---|
| Medicines4 | ||
| Dolutegravire.g. Tivicay, Dovato | Calcium can substantially lower dolutegravir blood levels (chelation). The FDA labels advise dolutegravir 2 hours before or 6 hours after calcium supplements.1 | Drug label |
| Levothyroxine | Calcium carbonate can reduce levothyroxine absorption; the FDA label says to avoid taking them within 4 hours of each other.1 | Drug label |
| Quinolone antibioticse.g. ciprofloxacin, gemifloxacin, moxifloxacin | Taken together, calcium reduces quinolone absorption; ODS reports separating them by 2 hours prevents this.1 | NIH fact sheet |
| Lithium | Long-term lithium can raise blood calcium, and adding calcium supplements could increase this risk.1 | NIH fact sheet |
Check with what you take
Kept on this device onlyAdd what you take. We list every interaction our evidence profiles cite between Lithothamnion and your picks, and between your picks.
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Add a supplement or medicine you take to check it against Lithothamnion.
Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.
Who should be careful
5 groups- High intakes
- The adult UL is 2,500 mg/day (ages 19–50) and 2,000 mg/day (51+) from food and supplements combined. Very high blood calcium is rare in healthy people but can cause constipation, nausea, fatigue, kidney problems and heart-rhythm problems.1
- Pregnancy and breastfeeding
- The calcium RDA does not rise in pregnancy or breastfeeding (1,000 mg a day at ages 19–50, 1,300 mg at 14–18), and the upper limit stays 2,500 mg (19–50) or 3,000 mg (14–18). No Aquamin trials enrolled pregnant or breastfeeding women.1
- Kidney stones
- ODS notes that higher intakes of supplemental calcium might raise the risk of kidney stones; the upper limits rest on observational Women's Health Initiative data, although two later systematic reviews found no such link.1
- Medicines
- Dolutegravir, levothyroxine, quinolone antibiotics and lithium interact with calcium supplements.1
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.1
How to read the label
What to check on the Supplement Facts panel.
How to read the label
3 checksCount the calcium
Check for added vitamin D
Where to buy Lithothamnion (Aquamin)
Products from brands we partner with that contain Lithothamnion (Aquamin). Check the amount per serving against the doses studied above, and the label for other ingredients.
Lithothamnion (Aquamin) products from partner brands
1 product Paid links · we earn a commission- HerbsProNOW Foods Red Mineral Algae, 180 Vcaps
4 capsules: 3,500 mg Aquamin (Lithothamnion) providing 1,000 mg calcium and 80 mg magnesium, plus 25 mcg (1,000 IU) vitamin D2; trials used 2,400 mg Aquamin (about 800 mg calcium) without vitamin D
$16.23one-timeChecked Oct 15, 2026
Frequently asked questions
Short answers to common questions; the numbers link to the sources below.
Common questions
6 answersDoes algae calcium build bone?
In 300 postmenopausal women over 24 months, Aquamin calcium did not change bone density compared with control, although bone-turnover markers fell more.2
Does it help knee arthritis?
Is too much calcium a concern?
Yes. ODS sets the adult upper limit at 2,500 mg a day (ages 19 to 50) and 2,000 mg a day from 51, counting food and supplements, and lists medicines that interact with calcium.1
Is algae calcium safe in pregnancy or breastfeeding?
No Aquamin trials enrolled pregnant or breastfeeding women. ODS sets the same calcium needs (1,000 mg a day at ages 19–50) and upper limit (2,500 mg) in pregnancy and breastfeeding as for other adults, counting food and supplements.1
Is it better absorbed than calcium carbonate?
One 12-woman single-dose study found different calcium and parathyroid hormone responses than calcium carbonate; no long-term absorption comparison exists here.6
Sources
10 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.
Sources cited on this page
10 sources- 1Calcium: Fact Sheet for Health ProfessionalsFact sheet NIH Office of Dietary Supplements, 2026 · ods.od.nih.gov
- 2Supplementation with calcium and short-chain fructo-oligosaccharides affects markers of bone turnover but not bone mineral density in postmenopausal women.RCT J Nutr, 2014 · PMID 24453130
- 3Effects of supplementation with a calcium-rich marine-derived multi-mineral supplement and short-chain fructo-oligosaccharides on serum lipids in postmenopausal women.RCT Br J Nutr, 2016 · PMID 26669430
- 4A natural mineral supplement provides relief from knee osteoarthritis symptoms: a randomized controlled pilot trial.RCT Nutr J, 2008 · PMID 18279523
- 5A natural seaweed derived mineral supplement (Aquamin F) for knee osteoarthritis: a randomised, placebo controlled pilot study.RCT Nutr J, 2009 · PMID 19187557
- 6Effect of Calcium Derived from Lithothamnion sp. on Markers of Calcium Metabolism in Premenopausal Women.Crossover RCT J Med Food, 2018 · PMID 29023178
- 7A Calcium-Rich Multimineral Intervention to Modulate Colonic Microbial Communities and Metabolomic Profiles in Humans: Results from a 90-Day Trial.RCT Cancer Prev Res (Phila), 2020 · PMID 31771942
- 8A multi-mineral intervention to improve disease-related and mechanistic biomarkers in ulcerative colitis patients: Results from a randomized trial.RCT PLoS One, 2025 · PMID 41359652
- 9A multi-mineral intervention is associated with improved intestinal permeability in patients with ulcerative colitis: results from a pilot trial.Open-label trial Front Med (Lausanne), 2026 · PMID 42440705
- 10The bioaccessibility and tolerability of marine-derived sources of magnesium and calcium.RCT Methods, 2024 · PMID 38608850
What changed
Every dated change to this page: what changed, who made it and why.
Change log
2 entries| Date | Change | Who and why |
|---|---|---|
| forms, who should avoid, label guide, FAQ | Added pregnancy and breastfeeding and kidney-stone notes from the NIH ODS calcium fact sheet (updated June 22, 2026), a 2024 tolerability trial of Aquamin F (PMID 38608850) to forms and a calcium-content label step, and a pregnancy FAQ. PubMed search 2020–2026 found no new outcome trials beyond those already cited; interactions match the ODS list. | Writer: Kymata Health EditorialTrigger: A–Z page audit |
| all | Initial editorial evidence review. Every PMID checked against NCBI E-utilities esummary (title, year, journal; none retracted) and each cited abstract read; numbers taken from the abstracts (full text or registry used only where noted). Funding disclosed per study: Marigot Ltd, maker of Aquamin (2008 and 2009 knee trials, full text); NIH (2020 colon trial; 2025 UC trial, with capsules donated by Marigot); the 2014/2016 postmenopausal trial, 2018 crossover and 2026 pilot abstracts name no funder (disclosed as not stated). Safety rows and interactions use only the NIH ODS calcium fact sheet (copied from our calcium page). Where to buy: NOW Foods Red Mineral Algae (Aquamin; label checked 2026-10-15). | Writer: Kymata Health EditorialTrigger: new page |
Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.