What is marine magnesium?
Aquamin® and
the ocean-mineral story.
Marine magnesium is magnesium taken from the sea. The best-known form, Aquamin® Mg, comes from the clean waters off the Irish coast and carries 72 trace minerals from seawater along with its magnesium. Here’s what marine magnesium is, what the research shows, how it compares with magnesium glycinate, and how to tell real marine magnesium from a label trick.
What is marine magnesium? The short answer
Marine magnesium is magnesium taken from seawater. Aquamin® Mg, the best-studied form, comes from the waters off the Irish coast and carries 72 trace minerals from the sea. In a laboratory digestion and gut-cell model, it released more magnesium than magnesium oxide and was on par with magnesium chloride. It pairs well with a gentle amino-acid form like magnesium glycinate.
Most magnesium supplements are made by joining magnesium to one partner — oxygen, citric acid or glycine. Marine magnesium starts somewhere else: the ocean, which is naturally rich in magnesium and dozens of other minerals. Think of it as magnesium that arrives with a little of the sea’s mineral mix still attached.
How marine magnesium is made
How is marine magnesium made?
Seawater is naturally rich in magnesium. Marine magnesium is drawn from seawater as magnesium hydroxide, keeping traces of the other minerals found in the sea.
Seawater is one of the richest natural sources of magnesium on Earth. To make marine magnesium, the magnesium is drawn out of clean seawater as magnesium hydroxide, a gentle mineral form. Because it comes from the sea, it keeps traces of the other minerals dissolved in seawater — which a lab-made magnesium salt doesn’t have.
Aquamin®: the best-known marine magnesium
What is Aquamin® Mg?
Aquamin® is made by Marigot in Ireland. Aquamin® Mg is the magnesium-rich form, from the clean waters off the Irish coast, with 72 trace minerals. A sister product, Aquamin® F, comes from mineral-rich red algae and is rich in calcium.
Aquamin® is made by Marigot, an Irish company that has specialised in ocean minerals for decades. Its magnesium-rich form, Aquamin® Mg, comes from the clean waters off the Irish coast and carries 72 trace minerals from seawater alongside its magnesium.1
Marigot also makes a sister product, Aquamin® F, from mineral-rich red algae (Lithothamnion) that slowly builds a calcium-rich skeleton on the North Atlantic seabed. That one is mainly a calcium source. When you read about “Aquamin”, it helps to know which of the two is meant: for magnesium, it’s Aquamin® Mg.
“Most magnesium is made in a factory from one partner. Marine magnesium starts in the sea — and brings a little of the ocean’s mineral mix with it.”
What makes marine magnesium different
The 72 trace minerals: what they add
What do the 72 trace minerals in marine magnesium do?
The sea holds small amounts of many minerals, and marine magnesium keeps traces of them. They’re present in tiny natural amounts — a bonus that comes with the magnesium, rather than a replacement for a multivitamin or a balanced diet.
Seawater contains small amounts of many minerals, from potassium and calcium to boron, zinc and selenium. Marine magnesium keeps traces of this natural mix. They come along in the small, natural amounts the sea provides — so think of them as a natural bonus that comes with the magnesium, while magnesium itself is the main event.
What the research shows
Is marine magnesium well absorbed?
In a 2018 laboratory study that copied human digestion and gut absorption, Aquamin® Mg released more magnesium than magnesium oxide and was on par with magnesium chloride, a well-absorbed form. A 2024 trial in older adults found an Aquamin® mineral supplement well tolerated over 12 weeks.
Researchers at University College Cork ran Aquamin® Mg through a laboratory model that copies human digestion, then tested how much magnesium crossed a layer of human gut cells. Aquamin® Mg released and delivered more magnesium than magnesium oxide, and performed on par with magnesium chloride, a well-absorbed form.1 That puts marine magnesium well ahead of oxide, the cheap form found in many tablets, which was only about 4% absorbed in a human study.2
A 2024 study from the same university went further. In the lab, Aquamin® Mg dissolved well through digestion, especially when taken with food. In people, a 12-week placebo-controlled trial in healthy older adults found a supplement combining Aquamin® Mg and Aquamin® F well tolerated, with no significant side effects.4
Marine magnesium benefits and side effects
What are the benefits of marine magnesium?
Marine magnesium supplies magnesium, which contributes to normal muscle function, normal functioning of the nervous system, the maintenance of normal bones and the reduction of tiredness and fatigue. It also brings small natural amounts of the sea’s other minerals, and it contains no animal ingredients, so it suits vegetarians and vegans.
Marine magnesium is mostly magnesium hydroxide, which is naturally rich in magnesium (about 40% by weight in the form tested in 2018).1 Magnesium hydroxide is the same compound used in “milk of magnesia”, so like most magnesium forms it can loosen stools at higher amounts. Taking it with a meal and staying within India’s daily allowance (440 mg for men, 370 mg for women, from food and supplements together) keeps it comfortable. Our magnesium side effects guide explains which forms loosen stools and why.
Like all magnesium, it should be kept apart from some medicines: thyroid tablets by about 4 hours, osteoporosis tablets by at least 2 hours, and tetracycline or quinolone antibiotics 2 hours before or 4 to 6 hours after.5 People with kidney disease should take magnesium only on medical advice.
Marine magnesium vs magnesium glycinate
Is marine magnesium better than magnesium glycinate?
Magnesium glycinate is the gentle, well-studied form with human trials for sleep, cramps and recovery, and it carries calming glycine. Marine magnesium brings ocean trace minerals and beat oxide in a lab model. They do different jobs, and they work well together.
| Feature | Marine magnesium (Aquamin® Mg) | Magnesium glycinate |
|---|---|---|
| Where it comes from | Seawater off the Irish coast | Magnesium bound to the amino acid glycine |
| What comes with it | 72 trace minerals from the sea | Glycine — about 2.7 g per 440 mg of magnesium |
| Absorption evidence | Beat oxide, matched chloride in a lab gut model | Beat oxide in human studies; gentle on the stomach |
| Human trials | Well tolerated over 12 weeks in older adults (with Aquamin® F) | Sleep (2025), pregnancy cramps, exercise soreness |
| Gentle on the stomach | Best taken with food | Gentlest common form |
| Best for | Adding ocean trace minerals; vegans | Daily evening use, sleep and recovery |
Magnesium glycinate has the strongest human evidence: a 2025 trial found it improved insomnia scores,3 and it carries glycine, an amino acid studied for sleep quality. Marine magnesium adds the ocean’s trace minerals. One is the dependable daily core; the other widens the mineral mix. See our glycinate vs citrate vs oxide guide for the full comparison of forms, and how much magnesium per day to add up magnesium from more than one source.
We start with the core: magnesium glycinate.
Our first product is the magnesium form with the strongest human evidence for sleep, cramps and recovery.
Magnesium Glycinate by Evo Hominus™
Launching first. 100% non-buffered magnesium glycinate: 440 mg of magnesium from 3,667 mg of fully reacted bisglycinate, with about 2.7 g of glycine and zero oxide. Three tablets a day (two for women).
See Magnesium Glycinate →Bioactive Multivitamin
Coming soon. Our daily multivitamin is in development. Join the waitlist to hear first when it launches.
Join the waitlist →How to check a marine magnesium label
How do I choose a good marine magnesium supplement?
“Marine magnesium” isn’t a protected term. Look for the named ingredient (such as Aquamin® Mg), the elemental magnesium per serving, and whether trace minerals are part of it.
A named source
“Aquamin® Mg” or a clear seawater origin, not just “marine magnesium”.
Elemental magnesium per serving
The magnesium you actually get, not the weight of the whole ingredient.
Calcium sold as magnesium
Algae-based “ocean minerals” are often mainly calcium — check the magnesium figure.
Magnesium oxide on the label
Some “marine” products are mostly oxide — the least absorbed form.
- The 2018 Aquamin® Mg absorption study used a laboratory model of digestion and human gut cells, not people.1 The 2024 human trial was small, in healthy older adults, tested Aquamin® Mg together with Aquamin® F, and looked at tolerability rather than absorption.4
- The 72 trace minerals are present in small, natural amounts; research on Aquamin® looks at the whole mineral mix rather than each trace mineral on its own.
- The 2025 sleep trial gave 250 mg of magnesium a day as bisglycinate, with a modest improvement.3
Marine magnesium, answered plainly.
What is marine magnesium?
What is Aquamin® Mg?
Is Aquamin® made from red algae?
Is marine magnesium well absorbed?
Is marine magnesium better than magnesium glycinate?
Is marine magnesium vegan?
Is every “marine magnesium” the same?
Which magnesium should I start with?
What are the benefits of marine magnesium?
Is marine magnesium the same as magnesium hydroxide?
Does marine magnesium have side effects?
What does “72 trace minerals” mean?
Where does Aquamin® come from?
Is marine magnesium good for sleep?
Is marine magnesium good for bones?
Can I take marine magnesium and magnesium glycinate together?
How much marine magnesium should I take?
When should I take marine magnesium?
Is marine magnesium better than magnesium oxide?
Is Aquamin® Mg the same as Aquamin® F?
Studies behind this guide
- Felice VD, O’Gorman DM, O’Brien NM, Hyland NP. Bioaccessibility and bioavailability of a marine-derived multimineral, Aquamin-Magnesium. Nutrients. 2018;10(7):912. PMC6073474 — Mg(OH)₂ from Irish coastal seawater with 72 trace minerals; INFOGEST digestion + Caco-2 cells.
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001;14(4):257–62. PMID 11794633
- Schuster J, Cycelskij I, Lopresti A, Hahn A. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep. 2025;17:2027–2040. PMID 40918053
- Dowley A, Long-Smith CM, Demehin O, Nolan Y, O’Connell S, O’Gorman DM. The bioaccessibility and tolerability of marine-derived sources of magnesium and calcium. Methods. 2024;226:28–34 — INFOGEST digestion; 12-week randomised, double-blind, placebo-controlled trial of Aquamin® Mg + Aquamin® F in healthy older adults.
- National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals — interactions with medications. ods.od.nih.gov
Nutrition Science Hub
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The main magnesium forms, compared on human studies.
Read the guide → MagnesiumHow much magnesium per day
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Read the guide → Magnesium in IndiaMagnesium deficiency in India
Symptoms, foods — and why a blood test can miss it.
Read the guide →