Luckily for us salt is one of the most common minerals on Earth and is formed mainly from sodium chloride. Salt is a crystalline solid and is white, light gray or pale pink in colour. Salt is an essential part of the diet for all humans and animals, and the sodium and chloride ions are necessary for our survival.

Salt plays an important part in the regulation of the fluid balance of the body.  Salt cravings can be caused by a deficiency of sodium chloride or by a lack of other trace minerals.  The salt that we use on our tables today is produced in several different forms, such as unrefined salt like sea salt, refined table salt, and iodized salt.  Salt is also an important preservative, and is used extensively to preserve food.  The flavour of salt is one of the basic tastes, making it one of the oldest and most commonly used seasonings.  In the Western world traditionally there are four taste sensations: sweet, salty, sour and bitter.  We lose salt from our bodies through sweating and excretion, so we constantly need to replace what we lose, especially in very hot weather.

However, too much salt in your diet can cause you to experience health problems, such as high blood pressure, heart disease and an increased risk of stroke. Having too much salt in your diet can also cause water retention. Fully grown adults should eat no more than 6g of salt a day, which is approximately a teaspoonful, and in the UK alone reducing the average daily salt intake by adults could prevent around 17500 premature deaths a year. Children and babies need a lot less salt than this. A baby only needs less than 1g of salt a day up until it is around a year old. Breast milk and infant formula contain the right levels of salt, but it is important not to add salt to baby’s food when they start eating solids and to not give them processed foods that are not specifically made for infants. Another benefit of reducing your salt intake is that you might begin to notice a broader range of flavours in your food.

Much of the salt we consume is hidden in the food that we eat, so it is not just the salt that we add to our food that is the problem. Foods that have a high salt content are processed foods, bread, cereals, salty snacks and foods that have been canned in brine or preserved in salt. They should be avoided or cut down on where possible, and replaced with fresh, home-cooked meals.

Iodine is also commonly added to salt, especially in inland areas where there is little iodine in the soil for the crops to absorb. A lack of iodine in the diet can lead to problems with the thyroid gland in the neck know as goitre. In the United Kingdom this was commonly known as ‘Derbyshire Neck’ as it was a condition particularly prevalent among the poorer sections of society in Derbyshire, particularly young women of child bearing age a century or so ago.

 In the UK, for the first time a 'salt cave' has been opened in South London. The 'salt cave' is a room with a coating of salt on the walls and floor and the air is full of salt particles.  Sitting in th 'salt cave' is supposed to be very healing for respiratory problems, and can aid in the clearing of mucous from the airways,reducing sinus infections, and helping people with asthma.

It is believed that we first started adding salt to our food when our early ancestors started cultivating crops in about 10,000 BC and started to eat less meat.  Earlier, prehistoric hunter gatherers had derived all the sodium that they needed from the large amounts of meat and fish that they ate.  They also discovered that you could use salt to preserve food, so that they could store it at times when food was plentiful to be used when the food supplies were running low. 

Early civilisations learned that they could obtain salt from dried out lakes, by boiling or evaporating sea water or mining for salt in areas where solid salt forms in the ground.  However, salt supplies remained scarce until modern times, and for most of recorded history salt was regarded as a rare and valuable commodity, due to the expense of extracting it and then conveying it overland or by sea.  In Iran in 2005 a group of salt mummies were discovered in ancient salt mines.  These were bodies of workers who had perished in the mines around 1700 years ago and whose bodies had been naturally preserved by the salt.

Taxes on salt were introduced by the ancient Chinese, and there were times when the revenues raised on salt made up half of the Chinese Empire’s tax revenues.  The Great Wall of China would probably never have been built without a salt tax!  The Romans also taxed salt and one of the famous Roman roads the ‘Via Salaria’ or salt road was built to transport salt.  The infamous French salt tax known as the ‘Gabelle’ was hugely unpopular with the French people.  It was first imposed in 1286 by King Philip IV and was not repealed until 1790.  There was also a long history of taxing salt in India, and the huge increase of this tax by the British which led to salt becoming unaffordable for a lot of Indians was one of the issues that  flared up and helped pave the way to Indian Independence.

It is said that in ancient times, when an enemy was conquered, the victorious army would sow salt into their fields so that they would not be able to grow their crops.  The most well known example is the Romans ploughing salt into the soil after they conquered Carthage in 146 BC, although this is disputed as it is not mentioned in ancient texts but is mentioned by the 19^th century German historian Ferdinand Gregorovius.

We still commonly use the term ‘above the salt’ and it originated in the Middle Ages when a salt cellar was placed on the dining table, and the important people of the household were seated ‘above the salt’ and the lesser folk and servants were seated on the other side.  The fact that salt was expensive was shown by the fact that these salt cellars in prosperous households were often, quite large, very ornate and made of precious metals.  Other phrases based on salt that we still use are ‘salt of the earth’ denoting a person who is very worthy which reflects how precious salt was, ‘taken with a pinch of salt’ which means that what has been said should not be taken too seriously, and ‘worth one’s salt’ which harks back to the custom of Roman Legionnaires receiving some of their wages in the form of salt.

Too much salt is toxic to many plants, and soil that contains too much salt is not suitable for agriculture and tends to be very unproductive.  Natural salt lakes tend to be very dry and arid areas.  Worryingly, salt sterilizing the soil in regions that are normally fertile is looming large as a major environmental and economic issue in some parts of the world.  In some parts of Australia, soil salinization is occurring in some regions partly due to sea salt being brought inland by wind and flooding and then being brought to the surface by modern farming practices such as irrigation and clearing the land.   The thin top-soil layers have become far too salty for successful agriculture and it is estimated that more than 2.5 million hectares of land has become unusable because of these modern farming practices

Finally, you would normally feel safe from a shark attack swimming in the fresh water of a river, right? Sharks live in the salt waters of the oceans, don’t they? Wrong! Bull sharks are considered by experts to be one of the three species of shark most likely to be aggressive to humans, along with great whites and tiger sharks. They generally live in shallow waters near the coast in tropical regions, but they are among the only sharks that can survive in brackish and fresh water. They have been spotted thousands of miles up the Amazon River, been caught 900 miles up the Mississippi River and leap the river rapids in Nicaragua to reach Lake Nicaragua which is inland. So that river you like to have a swim in might not be so safe at all!

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