Salt in your diet

Written by: 
Dr Sarah Brewer

We all know what salt looks like but do we know why our bodies need it or understand the dangers of eating too much? What's a safe amount? This page explains.

Salt (sodium chloride) is widely added to food to enhance its flavour, retain moisture and preserve foods. It is highly effective as a preservative, as bacteriaA group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. and moulds that normally spoil foods such as fish and meats cannot survive in salty environments.

Why we need salt

When common table salt dissolves it breaks up into two types of ion (ions are essentially atomsThe smallest units of an element. or groups of atomsThe smallest units of an element. that have electric charges). These ions are sodium and chloride. Most sodium in the body is found outside the cells, in the surrounding fluids.

Sodium pumps in the cellThe basic unit of all living organisms. walls actively force sodium out of the cells, while forcing potassium ions into the cells. This exchange generates a small, negative electric charge which is vital for life. Without it, nerveBundle of fibres that carries information in the form of electrical impulses. and brain cells couldn't pass messages to one another, and heart muscleTissue made up of cells that can contract to bring about movement. cells would not be able to contract. A certain amount of salt is therefore essential for good health.

Dangers of excess salt

Our prehistoric ancestors evolved on a diet providing around 1g of salt per day.1 Our consumption has now escalated to around 9-12g salt per day on average. This tenfold rise in sodium intake has been blamed for the rise in blood pressure seen with increased age.

When a food label gives salt content as 'sodium', the figure needs to be multiplied by 2.5 to give table-salt content

The kidneys of many people are unable to excrete the large amounts of salt found in a typical Western diet.1 The retained salt stimulates thirst and causes fluid retention, which is thought to cause the rise in bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure.2

Excess salt is also linked with increased thickness (hypertrophyAn increase in the size of a tissue of organ resulting from an increase in the size of its individual cells.) of the left ventricleEither of the two lower chambers of the heart, or any of the four cavities within the brain. of the heart, which makes it pump less efficiently.3 In addition, and independent of its effects on bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure, too much salt in the bloodstream causes narrowing and stiffness of arteries.3

Because of these adverse effectsUndesirable side-effects of medication. on the heart and circulation, it is estimated that reducing average salt intake by 3g per day (for example, from 12g down to 9g) could reduce the risk of stroke by 13% and of coronaryRelating to the arteries supplying the heart itself. heart disease by 10%.

Restricting salt intake to 6g per day could double the benefits, while restricting salt intake to 3g daily might nearly triple them, reducing strokes by about a third and coronaryRelating to the arteries supplying the heart itself. heart disease by about a quarter.4

Learn more about Blood pressure management.

Cutting back on salt intake

Ideally, an adult should obtain no more than 6g of salt per day. Most of the salt we take in is hidden in processed foods such as canned products, ready-prepared meals, biscuits, cakes and breakfast cereals.

To reduce salt intake, avoid adding salt during cooking, or at the table, and minimise your intake of:

  • obviously salty foods such as crisps, bacon, salted nuts
  • tinned products, especially those canned in brine
  • cured, smoked or pickled fish or meats
  • meat pastes and patés
  • ready-prepared meals
  • packet soups and sauces
  • stock cubes and yeast extracts.

It also helps to check food labels and select brands with the lowest salt content.  Some foods are more salty than sea water, which contains 2.5g of salt per 100g of water!

Note that when a food label gives salt content as 'sodium', the figure needs to be multiplied by 2.5 to give table-salt content: for example, if a serving of soup contains 0.4g sodium this is the equivalent of 1g of salt (sodium chloride).

A good general rule is that, per 100g of food (or per serving if a serving is less than 100g):

  • 0.5g sodium or more is a high level of sodium
  • 0.1g sodium or less is a low level of sodium.

It is easy to replace salt with herbs and spices in cooking and at the table.

References: 
  1. de Wardener H E. 'Sodium and hypertensionHigh blood pressure..' Arch. Mal. Coeur Vaiss. 1996; 4: 9-15
  2. de Wardener H E, He FJ, MacGregor GA. 'Plasma sodium and hypertensionHigh blood pressure..' Kidney Int. 2004; 66(6): 2454-66.
  3. Menetron P, Jeunemaitre X, de Wardener HE, et al. 'Links between dietary salt intake, renal salt handling, bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure, and cardiovascular diseases.' Physiol Rev. 2005; 85(2): 679-715.
  4. He F J, MacGregor G A. 'How far should salt intake be reduced?' Hypertension. 2003; 42(6): 1093-9.