Home Ingredients CAS (Calcified Atlantic Seaweed Calcium)
Bone Health

CAS (Calcified Atlantic Seaweed Calcium)

Lithothamnion calcareum
Evidence Level
Limited
1 Clinical Trial
3 Documented Benefits
2/5 Evidence Score

CAS is a plant-source calcium from calcified Atlantic red seaweed (Lithothamnion), which also supplies magnesium and small amounts of other minerals. The 70-plus trace minerals figure comes from supplier literature, and nothing cited here shows those trace amounts matter. No human study of this seaweed calcium is cited on this page, so the bone evidence below is for calcium the mineral, not for this marine form.

Studied Dose Supplement labels commonly provide 500 to 1200 mg of elemental calcium per day, but the daily target is total calcium from food plus supplements, and most people already get part of it from food. Supplemental calcium is only useful to the extent your diet falls short. No published human bone trial of this seaweed calcium is cited here, so this is a general calcium dose, not a studied dose of this form.
Active Compound Calcium (often with vitamin D and trace minerals for bone support).

Benefits

Bone density support

Calcium is the main structural mineral of bone; taken together with vitamin D, calcium supplementation raised bone mineral density in a 2020 meta-analysis of randomized trials in postmenopausal women. That pooled result is for calcium plus vitamin D in general, not for this seaweed source, and within the same analysis the total and lumbar spine gains held for calcium-fortified dairy foods rather than for supplements.

Supported by Trial 1

Bone maintenance with age

Adequate calcium intake across life supports the skeleton, and that means total intake from food and supplements together. Nothing cited here shows the seaweed form does this any better than ordinary calcium carbonate or calcium citrate.

Supported by Trial 1

Muscle and nerve support

Calcium is needed for normal muscle contraction and nerve signaling. That is standard physiology of the mineral in the diet, and no study cited here measured muscle or nerve outcomes with this ingredient or with any calcium supplement.

Supported by Trial 1

Mechanism of action

1

Bone mineralization

Calcium combines with phosphate to form the hydroxyapatite crystals that give bone its hardness and strength.

2

Calcium homeostasis

The body tightly regulates blood calcium; adequate intake spares calcium from being drawn out of bone.

Clinical trials

1
Calcium plus vitamin D and bone density: meta-analysis (not a study of seaweed calcium)
PubMed

Systematic review and meta-analysis of combined calcium and vitamin D supplementation on bone in postmenopausal women. (Liu et al. 2020, Food and Function)

Postmenopausal women in the pooled randomized trials. Those trials tested calcium supplements or calcium-fortified dairy, each with vitamin D; none of the pooled evidence is specific to calcified seaweed calcium.

Combined calcium and vitamin D increased total bone mineral density (SMD 0.537, 95% CI 0.227 to 0.847), lumbar spine BMD (SMD 0.233, 95% CI 0.073 to 0.392), arm BMD (SMD 0.464, 95% CI 0.186 to 0.741) and femoral neck BMD (SMD 0.187, 95% CI 0.010 to 0.364), and hip fracture incidence was lower (RR 0.864, 95% CI 0.763 to 0.979). Three caveats matter. The effect is for calcium and vitamin D taken together, so it is not an effect of calcium on its own. In subgroup analysis the total and lumbar spine gains came from calcium-fortified dairy foods rather than from the combined supplement, and calcium alone had no effect on femoral neck BMD. And nothing in this review is specific to calcified seaweed calcium.

Side effects and drug interactions

Common Potential side effects

Constipation, gas or bloating can occur. Because this calcium comes from a seaweed that takes up minerals from seawater, it can carry traces of arsenic, cadmium, lead and mercury; food regulators set limits for these in Lithothamnion, so look for a product with third-party heavy-metal testing.
Take with food in divided doses of 500 mg or less at a time for best absorption. Seaweed calcium is mostly calcium carbonate, which needs stomach acid, so it is absorbed less well on an empty stomach and by people taking acid-reducing medication such as proton pump inhibitors.
Kidney stones: in a randomized trial of 36,282 postmenopausal women, 1000 mg of calcium with 400 IU of vitamin D daily raised urinary stone risk by about 17 percent (hazard ratio 1.17, 95% CI 1.02 to 1.34). That is an everyday supplement dose, not only very high intake. If you have had a kidney stone, ask your doctor before taking supplemental calcium.

Important Drug interactions

Antibiotics (tetracyclines, quinolones), thyroid medication, and bisphosphonates — separate by 2 to 4 hours.
Thiazide diuretics — monitor calcium levels.
Tell your doctor about all medications and your total calcium intake.

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Frequently asked questions about CAS (Calcified Atlantic Seaweed Calcium)

What is CAS?

CAS is a plant-source calcium from calcified Atlantic red seaweed (Lithothamnion), which also supplies magnesium and small amounts of other minerals. The 70-plus trace minerals figure comes from supplier literature, and nothing cited here shows those trace amounts matter.

What is CAS used for?

CAS is researched primarily for Bone Health. Calcium is the main structural mineral of bone; taken together with vitamin D, calcium supplementation raised bone mineral density in a 2020 meta-analysis of randomized trials in postmenopausal women.

What is the recommended dosage of CAS?

The clinically studied dose is Supplement labels commonly provide 500 to 1200 mg of elemental calcium per day, but the daily target is total calcium from food plus supplements, and most people already get part of it from food. Always follow the product label and check with a healthcare provider for personal advice.

Is CAS safe, and does it have side effects?

For most healthy adults, CAS is well tolerated at studied doses. Reported effects can include: Constipation, gas or bloating can occur. Because this calcium comes from a seaweed that takes up minerals from seawater, it can carry traces of arsenic, cadmium, lead and mercury; food regulators set limits for these in Lithothamnion, so look for a product with third-party heavy-… It may also interact with some medications. CAS is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does CAS interact with any medications?

Possible interactions include: Antibiotics (tetracyclines, quinolones), thyroid medication, and bisphosphonates — separate by 2 to 4 hours. Thiazide diuretics — monitor calcium levels. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for CAS?

NutraSmarts rates the evidence for CAS as Limited (2 out of 5). It is backed by 1 clinical trial and 1 cited reference summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(1 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Liu C, Kuang X, Li K, et al. Effects of combined calcium and vitamin D supplementation on osteoporosis in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials. Food Funct. 2020;11(12):10817-10827..PubMedUsed to support: Meta-analysis of calcium taken together with vitamin D in postmenopausal women. It supports a bone density benefit for that combination in general, though its subgroup analysis located the total and lumbar spine benefit in calcium-fortified dairy rather than in the combined supplement. It is not specific to calcified seaweed, so it is borrowed evidence and cannot support any claim about this marine form.