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Can people drink seawater?

Can people drink seawater?
19. 6. 2020

Every schoolchild has been taught that seawater is undrinkable because it causes dehydration. There have, however, been several cases where people were shipwrecked on desert islands and survived for months despite only having access to a few litres of fresh water. How could they do it? Simply put – they found that diluted seawater is not only completely harmless, but even beneficial. As the renowned medieval physician Paracelsus observed: “Anything can be a poison. It is the dose that makes it poisonous.”

Can people drink seawater?

Seawater is four times saltier than our body fluids, which leads to a disruption of osmosis. To avoid poisoning the human organism, there are certain rules to be followed when drinking it. We can consume it in two ways:

  • In its pure form (known as hypertonic seawater), it can be used in small quantities that are not liable to cause dehydration.
  • It can be diluted with fresh water so that the concentration of ions matches that of our body fluids – the seawater is diluted 4× (in a ratio of 1:3; 1 part seawater + 3 parts fresh water) to create isotonic seawater.

Seawater is a rich source of minerals and other healthy elements that provide all sorts of benefits for the human body. Please bear in mind that it cannot replace fresh water and it cannot be consumed according to the same rules.

Isotonic vs. hypertonic water

Isotonic = 4× diluted seawater that has the same characteristics as the body’s internal environment and therefore places no stress on it. The recommended daily intake is 1 l of isotonic seawater, which can be made by mixing seawater and freshwater in a ratio of 1:3 (250 ml of seawater + 750 ml of fresh water). This is the recommended daily total and can be drunk in several portions.

Hypertonic = undiluted seawater, which can only be drunk in small doses. Its potential uses include cleansing the organism, rinsing the mouth or as a nasal spray.

Differences between salted water and seawater

You might ask: “Why should I drink seawater if I can just mix a couple of teaspoons of salt into tap water and be done?”
Cooking salt or common salt, NaCl (sodium chloride), can be found in nature in the form of a mineral known as halite. Cooking salt is a pure inorganic compound that does not offer such a wide range of benefits as seawater.
Why I don’t drink water with salt:

  1. Anyone who has ever tasted pure seawater, even by mistake, must surely admit that it is disgusting and absolutely unsuitable for drinking in large quantities. Water with salt is no better. When seawater is diluted, its saltiness is reduced and it becomes drinkable.
  2. Even pure sea salt dissolved in a glass of water does not provide the organic form of minerals (which depends on plankton) or any of other seawater compounds, such as amino acids, enzymes, vitamins, etc. Before evaporation, the minerals in seawater exist in an unbound form that is much easier for the body to absorb. After evaporation, the elements combine so that, for instance, sodium and chlorine ions merge into sodium chloride (cooking salt).
  3. Seawater contains about 10% less sodium than refined salt. Seawater provides a total of 78 vital minerals and trace elements that are filtered out in the production of cooking salt and which the body would have to obtain from other sources.
  4. When using pure (purified) sea salt, which can be distinguished by its dryness and white colour, whereas sea salt in its basic form is greyish and moist, a solution with around 5–8 minerals is obtained. All the other minerals are extracted for industrial use.
  5. A diluted solution of refined cooking salt and water contains sodium chloride, plus additives such as iodine and substances for bleaching and texture. 
  6. The salt processing industry removes 140 g of minerals from every 1 kg of salt for further industrial processing.
  7. An interesting piece of trivia: water covers 71% of our planet, of which 97% is seawater and 3% is fresh water. Of the 3% of water that is fresh water, humans use just 0.06%, of which 70% is used for irrigation, 20% for industry and 10% for domestic consumption.

Mineral water vs seawater

Mineral water or seawater? Which contains more beneficial substances? Which is better for the body? They both have a lot to offer, so judge for yourself.

The proper functioning of our bodies depends on a supply of nutrients from which they can extract the materials they need. From food and drink, the body extracts not just vitamins, enzymes and fatty acids, but also minerals, which are vital to many processes in the human body. If we are honest, we must admit that our food provides less of them than it did in our grandparents’ days, which is why many people are turning to nutritional supplements to top up on specific minerals. These include types of water with special contents.

Mineral water

Mineral water comes from natural underground sources that are rich in a variety of minerals. In Europe, it has long been synonymous with springs at spas. Their beneficial effects on the human body led to them being widely used at spas in baths, wraps or inhalations, but they can also be taken internally. The conditions mineral waters are used to treat depend on their chemical composition and physical properties. They help in the treatment of gout, kidney stones, skin problems, joint pain, diabetes and respiratory problems, amongst other diseases.

Seawater contains a wide range of substances in organic form, which makes them easier for the body to absorb and process. To achieve the desired effect, minerals should complement one another, preferably all at once, rather than in succession. In contrast to mineral water, seawater contains 78 minerals and trace elements, as well as several other beneficial substances. It thus contributes to the proper functioning of the human body. 

Chart 1: Graph of the levels of selected ions in mineral water and seawater

Data for Chart 1 - Mineral waters

Data for Chart 1 - Seawater

Graf zastoupení vybraných iontů v minerální a mořské vodě


Ion levels in mineral/sea water

Concentration (mg/l) - seawater

Chart 2: Graph of the levels of selected ions in body fluids (plasma = the fluid component of blood; interstitial fluid = fluid filling the space between cells; intracellular fluid = fluid inside cells)


Data for Chart 2

Graf zastoupení vybraných iontů v tělesných tekutinách


Ion levels in body fluids

Concentration (mg/l)

  • plasma
  • interstitial fluid
  • intracellular fluid

Chart 3: Graph of the levels of selected ions in seawater and 4× diluted seawater

 Graf zastoupení vybraných iontů v tělesných tekutinách a 4× zředěné mořské vodě


Comparison of ion levels in body fluids and 4x diluted seawater

Concentration (mg/l)

  • 4x diluted seawater
  • plasma
  • interstitial fluid
  • intracellular fluid

What can we conclude from this?

Chart 1 shows that seawater is richer in positive ions (Mg, Ca, Na, K), trace elements and other enriching substances, and sulphate anions.

Consumption of seawater has been shown to improve cholesterol levels and help prevent cardiovascular disease. It reduces blood pressure, the quantity of fat and body weight. It can help in the treatment of diabetes, cataracts, stomach ulcers or skin problems, and it protects the liver. It has also been shown to have therapeutic potential in the prevention of cancer growth and the treatment of osteoporosis.

Do you feel tired, is it difficult to get up in the morning, or do you seem drained of energy? Seawater can also help with these problems.

Groundwater is at risk of pollution from human activities such as agriculture, industry or logging. The use of inappropriate fertilisers, pesticides and other chemical preparations can affect the health of people who rely on groundwater.

There is still plenty of seawater on earth that has been relatively unaffected by human activity and is safe for drinking after basic cleaning processes. If it is used in line with recommendations, it can help both to prevent illness and improve existing conditions.

Seawater for daily use 

Incorporating seawater into your diet is an easy way to boost your immunity. It has no chemical additives, but 78 minerals that will fight for your health.

You can use seawater in cooking, to rinse cavities and to drink – when diluted 1:3. A two-litre bottle can be used to prepare 8 litres for drinking and costs just CZK 31.10. You can order this cheap and natural source of health from the sea in our e-shop.

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