Dr Rosemary Stanton

Read regular updates from nutritionist Dr Rosemary Stanton.

All about salt

Sorting out sodium and salt

Dr Rosemary Stanton, nutritionist

 

Some people are confused about salt and sodium. We usually talk about salt and doctors and health authorities often tell us our diets have too much salt, but the nutrition information panel on food labels lists sodium rather than salt.

Sodium and salt are related, but the terms are not inter-changeable. Basically, salt is sodium chloride, with sodium making up about 40% of salt. If you would like to translate this, 1000mg salt contains approximately 400 mg sodium.

Our bodies need sodium, not salt, as such. Sodium is essential to maintain the right balance of fluids inside and around every cell in the body and it plays a role in transmitting impulses along nerves and in muscles. Too little sodium would be hazardous to health, although it’s rare. Too much sodium is much more common and it’s also hazardous to health.

Although we all need some sodium, we don’t actually need to consume salt to get it. Sodium is present naturally in many foods. For example, an egg contains 70mg, each cup of milk has 120mg, 150g of meat, fish or chicken (without any added salt) has 90-120mg and there is also some sodium in vegetables such as spinach and celery.

The fact that sodium occurs naturally in foods is why food labels tell us how much sodium is present in a food. The sodium figure on the food label is the total of the natural sodium present in the food plus the sodium that has come from any salt added to the food. For example, cheese would contain the sodium from milk plus the sodium from the salt that is a vital part of manufacturing cheese.

Some people would like the food label to only list the salt content. This would lead to:

(a) a puzzle as to how or why salt was added to foods such as milk, eggs or fresh meat

Or

(b) an underestimate the total amount of sodium in the food.

For this reason, food labels will always list the sodium rather than the salt.

However, the ingredient list will include salt if it has been added.

 

Why is salt a problem ?

When we consume more sodium than we need, the excess should be excreted by the kidneys. During human evolution, however, when salt (and often food) was scarce, the kidneys developed the ability to retain sodium. This was important in those days when only fresh foods were consumed and total sodium intake was low.

When we consume salt, however, our total sodium intake tends to be high and the kidneys ability to retain sodium leads to retention of fluids. Extra fluid stretches the normal elasticity of the blood vessels and causes them to thicken and narrow (often called ‘hardening of the arteries’). After years of constant high sodium intake, the heart has to work harder to push blood through the stiffened arteries and blood pressure tends to rise. High blood pressure is a major risk factor for heart attack and also for stroke – the two most common causes of death in our society. High blood pressure also stresses the kidneys and we’re now seeing a big increase in kidney problems.

By age 60, half of all Australians have high blood pressure. By contrast, in populations with a low salt intake, such as the Kalahari Bushmen, the Yanomama Indians in South America and among some highlanders in Papua New Guinea, blood pressure does not rise with age and strokes and heart disease are virtually unknown. These groups are not genetically protected from high blood pressure, because if they change to a western diet with salted foods, their blood pressure rises.

There are some people who eat salt throughout life and never get high blood pressure. Unfortunately, we have no way of knowing who may be resistant to the harmful effects of salt. However, most research suggests that problems from a high salt intake begin in childhood.

Other health problems associated with too much salt include premenstrual syndrome, carpel tunnel syndrome and Meniere's syndrome, a disabling condition characterised by tinnitus, vertigo and, eventually deafness.

 

How much is too much ?

An adequate intake (AI) of sodium has recently been revised to 460 to 920mg/day for everyone over 14 years of age. The upper limit for safety has been set at 2300 mg/day.  Many people consume five to six times that amount.

For toddlers, the AI is 200-400mg of sodium, for 4-8 year-olds, 300-600mg and for 9-13 year-olds, 400-800mg. The most recent national nutrition survey found that 100% of children exceeded the upper limit for safety.

About three quarters of our sodium comes from the salt already added to processed foods. Fast foods, snack foods, savoury crackers, soups and sauces are obvious sources of salt, and salt is an essential ingredient of foods such as bread or cheese. Salt is also added to some cereals and processed meats can add a lot if they are consumed often.

A 30g serve of cornflakes with milk at breakfast, plus a cheese and ham sandwich for lunch will provide 1300 mg sodium – well above our daily needs. Switch to porridge with milk, and a roast chicken and salad sandwich and the sodium falls below 400 mg.

A diet based largely on fresh foods is the best way to keep sodium levels in check.

A large two-part trial of a diet dubbed the DASH diet (Dietary Approaches to Stop Hypertension) provided valuable information.  In the first stage of the DASH diet, participants ate a healthy diet with plenty of fresh fruit and vegetables, fresh meat and low-fat dairy products. Their blood pressure fell. In the second stage, when they were also asked to cut out added salt  and salted foods, their blood pressure fell further.

 

How to add flavour without salt

1. Go fresh as much as possible.

The fresher the food, the greater its natural flavour and the lower the need to add salt.

2. Cook with as little water as possible.

When fresh vegies are stir-fried or steamed, they have much more flavour (and more vitamins) than when they are boiled in water.

3. Seek out safe flavours.

Use any of the following to add flavour:

• Any herbs, fresh or dried
• Any spices, including freshly ground pepper
• Garlic
• Lemon juice
• Asian flavours such as Thai basil, lemongrass, coriander, ginger, garlic, galangal