Algas calcareas

Algas Calcareas: A Comprehensive Encyclopedic Reference

1. Identity: Botanical Names, Natural Source, and Taxonomy

Algas calcareas, also known as AlgaeCal, is a plant-based dietary supplement derived from Lithothamnion superpositum (also referred to commercially as Mesophyllum superpositum), a red marine algae native to South America, and is a source of calcium, magnesium, and other trace minerals. A closely related and extensively studied species used in similar supplements is Lithothamnion calcareum (Pallas), harvested from Atlantic waters.

Taxonomically, algas calcareas is red algae in the Rhodophyta phylum, from the Corallinales order, the Lithothamnion (or Mesophyllum) genus — one of the 103 species within that genus. These algae belong to the Corallinaceae family, which includes various species that absorb minerals directly from seawater.

Lithothamnion calcareum (LC) is a red macroalgae of the Corallinales order, whose unique feature is the abundant presence of calcium carbonates in its cell walls. The branded ingredient Aquamin® is derived specifically from Lithothamnion calcareum (and in some formulations Lithothamnion corallioides), found in the cold Atlantic waters off the southwest coast of Ireland and the northwest coast of Iceland.

The primary species used commercially in the "Algas calcareas" or AlgaeCal supplement is harvested from South America. AlgaeCal® is wild-harvested and derived from a South American marine red algae called Lithothamnion superpositum. This algae belongs to the Algas calcareas family of algaes. Note that the scientific literature discusses both the South American source species (L. superpositum/Mesophyllum superpositum) and the North Atlantic species (L. calcareum, L. corallioides) under the same common name; most peer-reviewed mechanistic and clinical research has been conducted on the North Atlantic species (Aquamin®), while the proprietary AlgaeCal product is derived from the South American species.

Common Names and Synonyms

• Algas calcareas, also known as calcareous algae, have gained recognition as a natural mineral supplement, especially valued for their highly bioavailable calcium and broad spectrum of trace elements.
• AlgaeCal® (proprietary brand, South American source)
• Aquamin® (proprietary brand, North Atlantic source, derived from Lithothamnion calcareum)
• Coralline algae; calcified red algae; marine red algae calcium

2. Natural Source and Harvesting

Algas calcareas are a type of red marine algae that accumulate calcium and other minerals from ocean waters, forming hard, mineral-rich structures. Over time, these algae settle and fossilize on the seafloor, where they are harvested and milled into a natural mineral supplement.

The South American variety follows a distinctive life cycle. These kiwi-sized balls of living algae attach to seaweed on the ocean floor, until they eventually detach and find their way to shore, where they can be harvested. The Algas calcareas naturally detach from seaweed and wash ashore, where the entire algae ball is then sustainably hand-harvested, sun dried, and milled into a powder, then cold processed to retain nutritional value.

For the North Atlantic variety (Aquamin®): during a five-year life span, these algae absorb essential minerals from the sea. The algae then break down naturally and settle on the sea bed. These calcified skeletal remains are harvested, washed, dried and milled and provided in a capsule formulation.

Lithothamnium Superpositum (or Algas Calcareas as the South American locals call it) is ecologically harvested in pure waters, as attested to by being certified organic by the USDA and IFOAM.

3. Chemical Composition and Key Constituents

The major elements of Lithothamnion calcareum extract are Ca and Mg (more than 20% and 4% by weight, respectively), but it also contains measurable levels of 74 other trace elements, including phosphorus. There are compositional differences between harvesting locations and processing methods.

For the branded Aquamin® (Atlantic source): the extract contains 12% Ca²⁺, 1% Mg²⁺, and detectable amounts of 72 trace elements, but essentially no organic material.

For the South American Algas calcareas raw material: the supplement is made by milling whole, live-harvested sea algae found on the South American coastline. In addition to calcium, the algae contained other naturally occurring minerals in the following rank-order of percentage: carbon, chloride, magnesium, manganese, selenium, silicon, sodium, strontium, titanium and vanadium, boron, silica, and copper.

The fossilized algae are composed of up to 34% calcium, along with magnesium, potassium, boron, zinc, and more than 70 trace elements.

Their porous, honeycomb-like matrix allows for high solubility and bioavailability, differentiating them from rock-based or synthetic calcium sources.

The main feature of Lithothamnion calcareum as a red alga of the Corallinacea family is the formation of calcium carbonate precipitate in its cell walls. The solubility characteristics of this mineral matrix are relevant to bioavailability: spectrophotometric determination showed that the calcium and magnesium contents were 30.01 and 6.22% (w/w), respectively. Solubilisation of calcium and magnesium was highly pH dependent.

Macro and Trace Mineral Profile

• Calcium: Principal mineral; present as calcium carbonate in the cell walls and skeletal matrix
• Magnesium: Second major mineral; present at approximately 1–6% by weight depending on source
• Additional minerals: besides calcium, this natural product contains magnesium, potassium, boron, copper, manganese, silicon, strontium, nickel, phosphorus, selenium, vanadium, and zinc
• Trace elements: Aquamin® contains detectable levels of 72 additional trace minerals including trace elements from the lanthanide family (essentially all of the minerals accumulated by the algae from seawater)

4. Traditional and Historical Use

Algas calcareas have long been used by ancient coastal cultures for bone strength and overall vitality. The documented traditional use is primarily associated with coastal South American communities who recognized the mineral-rich nature of these calcified marine organisms and used them as a natural source of minerals.

The name "Algas calcareas" — Spanish for "calcareous algae" — reflects the long-standing recognition of these organisms by South American coastal populations. The local South American name "Algas Calcareas" reflects the deep familiarity of regional populations with this organism, harvested from the pure waters of the South American coast.

In Brazil, L. calcareum is marketed as a nutritional supplement for calcium and other minerals under the pharmaceutical name of Vitality 50+®. The modern supplement tradition of Lithothamnion species as a calcium source in food and agriculture has European roots as well: Lithothamnion calcareum are authorized as vegetables and condiments in France, with certain specifications, including maximum allowed minerals and metals established by French legislature for these species when used in foods.

In the North Atlantic region, these calcareous algae have been harvested and used agriculturally for centuries as a soil amendment (known as "maerl") to reduce soil acidity, a practice that long predates their modern use as dietary supplements. The transition to human dietary supplementation is primarily a late 20th-century development driven by research into marine-sourced minerals as alternatives to conventional calcium carbonate supplements.

5. Mechanisms of Action

5.1 Calcium and Mineral Bioavailability

Calcium supplements derived from marine algae may have higher bioavailability than typical supplementation forms such as calcium carbonate, potentially leading to better outcomes on bone density.

Unlike traditional rock calciums, algae calcium is naturally full of dozens of trace minerals that support the metabolism of calcium in the body. These minerals have also been "predigested" by the plant, making them easier for the body to absorb.

It has been demonstrated that calcium derived from Lithothamnion sp. has superior bioavailability. Lithothamnion sp., a red algae of the Corallinaceae family, when harvested in its calcareous form, is rich in calcium, magnesium and a variety of trace minerals.

5.2 Osteoblast Stimulation and Bone Cell Activity

A recent in-vitro study demonstrated superiority over the two most commonly used calcium salts: calcium carbonate and calcium citrate. Cultured human osteoblast cells (hFOB 1.19) were treated with AlgaeCal, calcium carbonate or calcium citrate. Alkaline phosphatase activity was significantly increased with AlgaeCal treatment when compared to control, calcium carbonate or calcium citrate (4.0, 2.0 and 2.5-fold, respectively).

5.3 Colon Cell Differentiation

Proliferation and differentiation were assessed in a series of human colon carcinoma cell lines in response to a mineral-rich extract derived from the red marine algae, Lithothamnion calcareum. The extract contains 12% Ca²⁺, 1% Mg²⁺, and detectable amounts of 72 trace elements, but essentially no organic material. The red algae extract was as effective as inorganic Ca²⁺ alone in suppressing growth and inducing differentiation of colon carcinoma cells that are responsive to a physiological level of extracellular Ca²⁺ (1.4 mM). However, with cells that are resistant to Ca²⁺ alone, the extract was still able to reduce proliferation and stimulate differentiation.

5.4 Multimineral Synergy

The 'active ingredient' for the complex is difficult to determine. A number of the minerals in Aquamin may have anti-inflammatory and anti-oxidant properties which might directly and/or indirectly influence the efficacy of this unique complex.

In studies with human colon carcinoma cells in monolayer culture, Aquamin® was more effective than calcium alone at suppressing tumor cell growth and inducing differentiation. Whether Aquamin® will, ultimately, prove to be more effective than calcium alone as a colon polyp chemopreventive agent in humans remains to be seen.

6. Scientific Evidence by Area of Use

6.1 Bone Health and Bone Mineral Density

Bone health is the primary evidence base for algas calcareas/AlgaeCal supplementation, supported by multiple human studies, though with significant methodological limitations.

In Vitro Evidence

Cultured human osteoblast cells (hFOB 1.19) were treated with AlgaeCal, calcium carbonate or calcium citrate. Alkaline phosphatase activity was significantly increased with AlgaeCal treatment when compared to control, calcium carbonate or calcium citrate (4.0, 2.0 and 2.5-fold, respectively). This is an in vitro finding and does not constitute clinical evidence of efficacy in humans.

Animal Evidence

The purpose of one study was to determine whether a mineral-rich extract derived from the red marine algae Lithothamnion calcareum could be used as a dietary supplement for prevention of bone mineral loss. Sixty C57BL/6 mice were divided into three groups based on diet: the first group received a high-fat Western-style diet (HFWD), the second group was fed the same HFWD along with the mineral-rich extract included as a dietary supplement, and the third group was used as a control and was fed a low-fat rodent chow diet. Mice were maintained on the respective diets for 15 months. Female mice on the HFWD had reduced bone mineralization and reduced bone strength relative to female mice on the low-fat chow diet. The bone defects in female mice on the HFWD were overcome in the presence of the mineral-rich supplement. This is preclinical animal data.

Human Clinical Studies

Study 1 — Six-month comparative effectiveness study (2011): In both groups, no significant differences in BMD or related variables were found between volunteers and non-volunteers or between those who completed per protocol and those who were lost to attrition. Both groups experienced a significant positive mean annualized percent change (MAPC) in BMD compared to expectation [AlgaeCal 1: 1.15%, p = 0.001; AlgaeCal 2: 2.79%, p = 0.001]. Both groups experienced a positive MAPC compared to baseline, but only AlgaeCal 2 experienced a significant change [AlgaeCal 1: 0.48%, p = 0.14; AlgaeCal 2: 2.18%, p < 0.001]. No clinically significant changes in a 43-panel blood chemistry test were found nor were there any changes in self-reported quality of life in either group. Following The Plan for six months with either version of the bone health supplement was associated with significant increases in BMD as compared to expected. This was a comparative effectiveness study, not a randomized placebo-controlled trial, and the population comprised primarily women over 40. The absence of a placebo arm is a significant limitation.

Study 2 — Seven-year longitudinal trial (2016): A study published in the Journal of the American College of Nutrition (JACN) examined the safety and efficacy of a vitamin/mineral enhanced plant-sourced calcium supplement [AlgaeCal (AC)] in female consumers who had taken the supplement from 1 to 7 years. Consumers who had completed at least one dual-energy x-ray absorptiometry (DEXA) bone mineral density (BMD) scan (N = 172) and/or blood chemistry test (N = 30) and purchased AlgaeCal (AC) from 1 to 7 years were contacted and offered complimentary repeat tests. Researchers found that usage of the calcium supplement was associated with a 1.04% linear increase in BMD per year, amounting to a 7.3% total increase over the seven-year study period. The seven-year longitudinal study used the commercial AlgaeCal product that also contained magnesium, vitamins D3, K2, and C, strontium and boron. The researchers explained that, after midlife, normal age-related annual bone loss is about 1% per year.

Important limitations of the 7-year study: The study was an open-label, observational design rather than a placebo-controlled RCT. Furthermore, the study was industry-funded: the study was funded by AlgaeCal Inc. (Vancouver, Canada). Importantly, the supplement tested contained strontium, vitamins D3, K2, and C in addition to algas calcareas calcium, making it impossible to isolate the contribution of the algae calcium component specifically. Most studies focus on beneficial effects in animals, with more independent research needed to establish efficacy of algae-based calcium over other calcium supplements in humans.

6.2 Joint Health and Osteoarthritis

Research on joint health has been conducted primarily using Aquamin® (Lithothamnion calcareum/corallioides), the North Atlantic version of calcareous red algae.

Randomized controlled pilot trial — knee osteoarthritis (2008): This small, pilot study evaluated the impact of treatment with a natural multi-mineral supplement from seaweed (Aquamin) on walking distance, pain and joint mobility in subjects with moderate to severe osteoarthritis of the knee. Subjects (n = 70) with moderate to severe osteoarthritis of the knee were randomized to four double-blinded treatments for 12 weeks: (a) Glucosamine sulfate (1500 mg/d); (b) Aquamin (2400 mg/d); (c) combined treatment composed of Glucosamine sulfate (1500 mg/d) plus Aquamin (2400 mg/d) and (d) Placebo. Fifty subjects completed the study and analysis of the data showed significant differences between the groups for changes in WOMAC pain scores over time (p = 0.009 ANCOVA); however, these data must be reviewed with caution since significant differences were found between the groups at baseline for WOMAC pain and stiffness. The baseline imbalance is a meaningful methodological limitation.

Second randomized, placebo-controlled pilot trial — NSAID reduction: A calcium and magnesium-rich seaweed-derived multi-mineral supplement, Aquamin, was investigated in two similarly designed trials. One trial showed improved symptoms of OA including improved WOMAC Osteoarthritis Index scores and walking distances in subjects consuming Aquamin compared to placebo. The study tested whether Aquamin supplementation could allow reduced NSAID usage over three months in subjects with moderate to severe OA of the knee. Subjects received pre-packaged two-piece hard shell capsules containing either Aquamin (267 mg Aquamin + 167 mg maltodextrin, yielding 34% calcium, 88.1 mg) or placebo (434 mg maltodextran). Subjects were instructed to consume three capsules, with a glass of water, three times per day.

In a previous study, osteoarthritis subjects treated with Aquamin showed significant improvement in the WOMAC scores for pain, stiffness, activity and composite scores over the course of the 12-week treatment, in comparison to subjects in the Placebo group.

Pilot RCT — mineral-rich algae vs. glucosamine (2020): A randomized controlled pilot trial found that mineral-rich algae with pine bark improved pain, physical function and analgesic use in mild-knee joint osteoarthritis, compared to Glucosamine. This study used Aquamin in combination with pine bark extract (Pycnogenol), making it difficult to isolate the contribution of the algae minerals alone.

Evidence strength for joint health: Evidence is preliminary. All joint health trials have been small pilot studies with limited power, short durations (12 weeks), and in some cases methodological limitations (baseline imbalances, lack of full blinding in outcome assessment). Several clinical trials have affirmed that Aquamin can help improve various aspects of bone and joint health, especially in people with osteoarthritis or otherwise low levels of calcium. Independent replication in larger, adequately powered randomized controlled trials is needed.

6.3 Gastrointestinal Health and Colon Cancer Prevention

Research in this area is predominantly preclinical (in vitro and animal models), with some early human mechanistic work.

In vitro (human colon carcinoma cell lines): A study demonstrated that a mineral-rich material derived from the red algae, Lithothamnion calcareum, is capable of suppressing the growth of human colon cancer cell lines in vitro. The mineral-rich extract is effective in slowing proliferation and inducing differentiation. With cells that are resistant to Ca²⁺ alone, the extract was still able to reduce proliferation and stimulate differentiation. These are in vitro findings only and do not establish efficacy in humans.

Animal study — colon polyp prevention: The purpose of one study was to determine whether a mineral-rich extract derived from the red marine algae, Lithothamnion calcareum (Pallas), could be used as a dietary supplement for chemoprevention against colon polyp formation. Researchers had shown that a multi-mineral extract from the marine red algae suppresses colon polyp formation and inflammation in mice. Ultimately, only a study in humans can determine whether or not the algae extract will have effective chemopreventive activity against colon cancer.

90-day human colonic microbiome trial: Aquamin is a calcium- and magnesium-rich natural product obtained from the skeletal remains of red marine algae of the Lithothamnion genus. In addition to calcium and magnesium, Aquamin contains detectable levels of 72 additional trace minerals including trace elements from the lanthanide family. A 90-day trial in healthy human subjects investigated effects on colonic microbial communities and metabolomic profiles. Aquamin has been used in past clinical studies in human subjects with no serious safety or tolerability issues reported. This research area is early-stage; no firm conclusions about colon cancer prevention in humans are supported by available evidence.

6.4 Dental and Oral Health

The current management of oral conditions such as dental caries and erosion mostly relies on fluoride-based formulations. Researchers have proposed the use of the remaining skeleton of Lithothamnion calcareum (LC) as an alternative to fluorides.

Overall, results from one study led to the conclusion that the extract of marine algae Lithothamnion calcareum, derived from the Atlantic waters of the northeast coast of Brazil, exerted an equivalent to superior modulatory effect on the enamel de-remineralization dynamics when compared to sodium fluoride. This was an in vitro study; the findings have not been confirmed in clinical trials.

Two experimental approaches tested the general hypothesis that LC could mediate enamel de-remineralization dynamics as efficiently as fluorides. Firstly, the effect of LC on enamel de-mineralization was determined in vitro by microhardness and gravimetric measurements to test the hypothesis that LC could either prevent calcium/phosphate release from intact enamel or facilitate calcium/phosphate reprecipitation on an artificially demineralized enamel surface. Evidence for oral health benefits in humans is preclinical/in vitro only at this time.

7. Body Systems and Health Areas of Association

• Skeletal system: Primary association; calcium and multimineral supplementation for bone mineral density maintenance and increase, prevention of osteoporosis
• Musculoskeletal system / joints: Joint pain and mobility in osteoarthritis; potential reduction of NSAID requirement
• Gastrointestinal tract: Colon epithelial cell differentiation, colon polyp chemoprevention (preclinical only); colonic microbiome modulation (early human data)
• Oral / dental health: Enamel remineralization (in vitro only)
• Mineral metabolism: Calcium and magnesium homeostasis; multimineral support for metabolic pathways dependent on these nutrients

8. Dosage Forms and Dosages Reported in Studies

Dosage Forms

Algas calcareas/calcareous red algae supplements are commercially available in the following forms:

• Vegetable capsules (most common)
• Powder (raw milled algae)
• Incorporated into multi-ingredient bone health supplement formulas

Dosages Used in Published Studies

• Bone density human studies (AlgaeCal): 3 vegetable capsules providing calcium (from AlgaeCal®) 750 mg; magnesium (from AlgaeCal®) 65 mg; vitamin D3 1000 IU.
• Osteoarthritis RCT (Aquamin): Aquamin administered at 2400 mg/d for 12 weeks.
• NSAID-reduction OA pilot study: 267 mg Aquamin per capsule (yielding 88.1 mg calcium at 34%), administered as three capsules three times per day.
• Gastroprotective rodent study (for reference to tolerable range): Doses of 30, 120 and 480 mg/kg were used in the gastroprotective study on Wistar rats. A dose of 2000 mg/kg was used in the preclinical acute toxicity study and oral doses of 1000 and 2000 mg/kg were used in the subchronic toxicity evaluation.
• Developmental toxicity study in rats: Daily administration of AlgaeCal by oral gavage at dose levels of 0, 500, 2500, and 5000 mg/kg/day during gestation days 5–19.

Note: Dosages in animal studies are not directly translatable to human dosing. The human doses reported are those used in published clinical studies only.

9. Safety Considerations

9.1 Acute Toxicity

Under the conditions of one study, the acute oral LD50 of AlgaeCal (AC) was found to be greater than 5000 mg/kg body weight in rats, while the single acute dermal LD50 was greater than 2000 mg/kg body weight.

In an acute toxicity test, mice (n = 20, 10 male, 10 female) were administered a single dose of 10 g/kg BW of Lithothamnion sp. No mortality, or signs of toxicity were observed.

9.2 Subchronic and Repeated-Dose Toxicity

L. calcareum played no significant role in the protection of the rats' gastric mucosa, nor did it cause increase in gastric irritation. No impact on the acute toxicity test was identified. In the subchronic toxicity test, serum levels of albumin, total protein and calcium decreased, and creatinine levels increased, suggesting hypercalcemia and possible kidney damage at high doses in rodents. This is a signal that warrants attention at very high intake levels, though it was observed at supratherapeutic doses in animals.

9.3 Skin and Eye Irritation

The primary skin irritation index of AlgaeCal (AC) was found to be 0.4 and classified as slightly irritating to the skin. In primary eye irritation studies, the maximum mean total score of AC was observed to be 13.7 and classified as mildly irritating to the eye. These classifications were made in the context of direct topical exposure and are relevant primarily for handling of the raw material.

9.4 Developmental Toxicity

An independent set of studies was conducted to obtain preliminary data for the teratogenic effects of AlgaeCal in pregnant rats from repeated gestational exposure, via oral gavage, over a test period of implantation through gestation (gestation days 5–19). Under the conditions of this pilot study, the effect of daily administration of AlgaeCal by oral gavage at dose levels of 0, 500, 2500, and 5000 mg/kg/day during gestation days 5–19 of a 21-day pregnancy appeared to result in no adverse toxicological effects to the pregnant rat or its developing offspring.

9.5 Heavy Metal Content

The plant accumulates calcium, magnesium carbonate and a large array of trace elements in its fronds from seawater over its life span. Elements that have the potential to cause harm (e.g. arsenic, lead etc.) are accumulated in such small amounts that they occur well below published safe limits, and as such, are considered harmless.

In France, regulatory limits have been established for this species in food applications: maximum allowed minerals and metals for Lithothamnion calcareum when used in foods include inorganic arsenic <3 mg/kg DW; cadmium <0.5 mg/kg DW; mercury <0.1 mg/kg DW; lead <5 mg/kg DW; tin <5 mg/kg DW; and iodine <2000 [mg/kg DW].

9.6 Human Clinical Safety

No clinically significant changes in a 43-panel blood chemistry test were found, nor were there any changes in self-reported quality of life in either group, and no adverse effects were reported in either group in the six-month comparative effectiveness study in women over 40.

Aquamin has been used in past clinical studies in human subjects with no serious safety or tolerability issues reported.

Findings from toxicological evaluation indicate that AlgaeCal® is well-tolerated with no significant adverse effects observed in organ health or motor activity across both male and female subjects.

9.7 Regulatory Status

The mineral extract (Aquamin® from Marigot, Ltd.) is sold as a food supplement under GRAS designation (GRAS 000028) in the United States, meaning it has been self-affirmed as generally recognized as safe. Aquamin contains detectable levels of 72 additional trace minerals and is sold as a food supplement (GRAS 000028; Marigot Ltd.) and is used in various products for human consumption in Europe, Asia, Australia, and North America.

9.8 Notable Interaction and Use Considerations

As a calcium-rich supplement, algas calcareas shares the pharmacodynamic interaction profile of calcium supplements generally. Calcium can reduce the absorption of certain minerals (e.g., iron, zinc) and some medications (e.g., bisphosphonates, tetracycline antibiotics, levothyroxine) when taken concomitantly. The subchronic animal data indicating possible hypercalcemia signals that excessive intake beyond recommended doses warrants monitoring of serum calcium and renal function, consistent with any calcium supplementation program at high doses.

The 7-year human study formulation contained strontium (as strontium citrate), vitamins D3, K2, and C, in addition to algas calcareas calcium. The seven-year longitudinal study used the commercial AlgaeCal product that also contained magnesium, vitamins D3, K2, and C, strontium and boron. Strontium has its own known bone-modifying effects and can artifactually elevate DEXA BMD readings due to its higher atomic number compared to calcium; this is a recognized confounder in interpreting BMD results from studies using strontium-containing formulas.

10. Summary of Evidence Strength

The overall evidence base for algas calcareas/calcareous red algae supplements can be summarized as follows:

• Bone mineral density: Multiple human comparative effectiveness studies show positive BMD changes, with the 7-year longitudinal study being the most substantial single piece of evidence. However, the lack of randomized, placebo-controlled trials without co-interventions (strontium, vitamin D, vitamin K2), combined with industry funding and open-label designs, limits causal inference. Notwithstanding the absence of a randomized clinical trial, findings warrant further study in view of the unusual increases in bone mineral density in both study groups.
• Joint health / osteoarthritis: Evidence is preliminary (small pilot RCTs), with some positive signals on WOMAC pain scores but methodological limitations including baseline imbalances and short follow-up.
• Gastrointestinal and colorectal cancer prevention: Primarily preclinical (in vitro and animal); human mechanistic data are early-stage. Only a study in humans can determine whether or not the algae extract will have effective chemopreventive activity against colon cancer.
• Dental enamel remineralization: In vitro only; no clinical trials in humans.

References

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