Is Salt Water High in Magnesium? A Deep Dive into Seawater Minerals

November 15, 2025 •

3 min read

With an average concentration of around 1,290 parts per million (ppm), seawater is indeed high in magnesium, making it one of the most abundant minerals in the ocean's composition. This vital element plays a crucial role in marine ecosystems and holds recognized health benefits for humans.

Quick Summary

Seawater contains a high concentration of magnesium, the fourth most common dissolved ion. The mineral-rich composition offers various transdermal health benefits, differentiating it significantly from tap water.

Key Points

High Magnesium Concentration: Seawater typically contains approximately 1,290 ppm of magnesium, a concentration significantly higher than most freshwater sources.
Rich Mineral Profile: Magnesium is the fourth most abundant ion in the ocean, contributing to a complex mineral-rich environment.
Transdermal Absorption: The magnesium in salt water can be absorbed through the skin when bathing or swimming, offering therapeutic benefits without needing to be ingested.
Benefits for Skin and Muscles: This absorbed magnesium can help improve skin hydration, reduce inflammation, and aid in muscle relaxation and recovery,.
Not for Drinking: Despite its high magnesium content, drinking seawater is dangerous and causes dehydration due to excessive sodium levels.
Not All Salt Water is Equal: The magnesium content varies drastically between natural sources like seawater and simple saline solutions made with refined table salt.

The Mineral Composition of Seawater

Seawater is a complex solution with many dissolved salts and minerals. Sodium chloride is the most abundant, but magnesium is also a major component. Typical seawater contains around 1,290 ppm of magnesium, or 1.29 grams per kilogram,. This makes magnesium the second most abundant positive ion after sodium. Concentrations can vary geographically but remain consistently high compared to other water sources.

Magnesium's Abundance in the Ocean

Magnesium enters the ocean through geological processes like erosion and runoff from rocks and soils. Magnesium salts are highly soluble, remaining dissolved rather than settling out. This continuous influx from land and volcanic activity maintains the ocean's high magnesium levels.

How Does Salt Water's Magnesium Compare?

Here is a comparison of typical magnesium levels in different water sources:


Water Source	Typical Magnesium Content	Notes
Seawater	1,290 ppm (1,290 mg/L)	High, stable concentration.
Deep Sea Water	Up to 1,430 ppm (1,430 mg/L)	Higher purity and mineral content.
Freshwater	A few to 50 ppm	Varies greatly and is generally low.
Hard Water	Up to 150 ppm	Naturally contains higher magnesium and calcium.
Magnesium-Enriched Water	30–120 ppm or more,	Artificially supplemented.

Health Benefits of Magnesium from Salt Water

The high magnesium in salt water, like the Dead Sea, is known for therapeutic effects. However, drinking seawater is dangerous due to high sodium,. External absorption through the skin (transdermal absorption) offers potential health benefits.

The Role of Transdermal Absorption

Magnesium can be absorbed through the skin while bathing or swimming in mineral-rich water. This is the basis for spa treatments using salts like Epsom salts or Dead Sea salts. Bathing in magnesium-rich solutions may:

Enhance Skin Hydration: A study found Dead Sea salt baths improved skin hydration, roughness, and inflammation in dry skin, possibly due to magnesium's ability to bind water and support the skin barrier.
Reduce Stress and Promote Relaxation: Magnesium is important for nerve and muscle function. Absorbing it through the skin may calm the nervous system, potentially reducing stress and improving sleep.
Soothe Muscles: Mineral soaks can help with muscle soreness and recovery. Magnesium regulates muscle contractions and can relieve cramps.

Natural vs. Artificial Sources of Magnesium Water

The magnesium content varies in different types of 'salt water'.

Natural Seawater: A direct source with a complex mix of minerals, not just sodium and chloride.
High-Mineral Salts (e.g., Dead Sea Salt): From very salty water bodies, known for high magnesium, used in baths and spa products.
Purified Seawater Extracts: Used in supplements to isolate magnesium and trace minerals.

Conclusion: The Mineral-Rich Truth

Natural salt water, especially seawater, is high in magnesium due to geological processes and the solubility of magnesium salts. While drinking it is unsafe, external use through swimming or bathing with mineral salts allows transdermal absorption. This can provide benefits for skin health, muscle relaxation, and general wellness, supported by scientific research.

For further scientific information on this topic, consult the study: "Bathing in a magnesium-rich Dead Sea salt solution improves skin barrier function, enhances skin hydration, and reduces inflammation in atopic dry skin".

Frequently Asked Questions

Seawater has a high concentration of magnesium, averaging around 1,290 parts per million (ppm). This varies slightly depending on the specific location and salinity levels, but it is consistently a significant component of ocean water.

No, it is not safe to drink seawater. The very high concentration of sodium chloride will cause severe dehydration, overwhelming the body's kidneys and leading to a dangerous imbalance of electrolytes.

You can safely absorb magnesium from salt water through your skin via transdermal absorption. This can be achieved by swimming in the ocean, taking a bath with magnesium-rich salts (like Dead Sea or Epsom salts), or using mineral-based skincare products.

Table salt is highly refined sodium chloride and contains only trace amounts of other minerals. Unrefined sea salt, on the other hand, contains a wider spectrum of minerals, including magnesium, due to its natural evaporation process.

Yes, studies have shown that bathing in magnesium-rich salt water can help improve skin barrier function, increase hydration, and reduce inflammation, which can be beneficial for conditions like eczema and dry skin.

Yes, the Dead Sea is an extreme example of a hypersaline lake with a much higher concentration of magnesium than the average ocean. The concentration is reported to be up to 198 mmol/L, or approximately 4.8 g/L (4,800 ppm).

While transdermal absorption is beneficial, it is not considered a reliable primary source for addressing a systemic magnesium deficiency. Dietary intake and oral supplements are the most effective methods for ensuring adequate magnesium levels.