Sodium occurs naturally
in many foods and is also added in the form of salt or other sodium-containing
substances. Common salt or table salt is a chemical compound of sodium
and chlorine and is called sodium chloride. The sodium content of food
has important implications for health. Salt contains about 40 per cent
sodium, and a teaspoon of salt, which weighs about 5 grams, contains
about 2 grams of sodium.
Rock salt and sea
salt are almost entirely sodium chloride, with only traces of other
elements (minerals). In contrast to pepper, which loses flavour once
ground, there is no advantage in freshly grinding salt prior to its
use. Iodized salt contains about 0.03 milligram of iodine per gram of
salt. It is intended as a supplement for people whose diet is deficient
in iodine. Recent findings in the U.S.A. indicate that the level of
iodine in the diet has increased and that the widespread use of this
salt is unnecessary.
of sodium are added to food, but not always in the form of salt. Common
food additives, such as baking soda, some preservatives, and monosodium
glutamate (MSG), also contribute to the total amount of sodium we consume.
AND HIGH BLOOD PRESSURE
of the population, because of genetic predisposition, may be increasing
their risk of high blood pressure (hypertension) by having a high intake
of sodium. People who have a high intake of sodium have a high incidence
of hypertension and stroke. High blood pressure is rarely seen in those
who consume less than 1.2 grams (1200 milligrams) of sodium per day.
In Australia, on the other hand, where the sodium intake can be in the
region of 4 to 8 grams per day, about one in five adult Australians
has high blood pressure. Salt is not necessarily the only important
factor leading to high blood pressure, but in some cases it is. There
are sound reasons why Australians should reduce their sodium intake.
But sodium is an essential nutrient, and we need a certain amount for
normal body function. A safe intake is considered to be between 0.9
and 2.3 grams of sodium per day, although in special circumstances,
such as excessive sweating and diarrhoea, higher levels may be needed.
There is usually
no need to increase salt intake in hot climates to avoid cramps, fainting
and other symptoms because the body's hormones will adjust over a few
days and conserve body sodium. Excessive heat presents other risks and
should, in any case, be avoided.
CAN WE CONTROL OUR SALT INTAKE?
Some people find
it hard to reduce their intake of sodium. We all have the ability to
taste salt, but the extent to which we like our food salted can be modified
by experience. The amount of salt we consume cannot be wholly controlled
by the moderate use of the salt shaker at the dinner table. This use
only accounts for about one-third of our daily intake. Up to half of
our salt intake is from processed food, with the balance occurring naturally
in food and water. The amount consumed in processed food is difficult
to control, although with highly salted foods, taste is a reliable guide.
Some items that do not taste highly salted can contribute significant
quantities of sodium to our diet because of the amounts we consume.
Examples include bread, tomato sauce, and cakes and biscuits. Many 'take-away'
foods, such as fish and chips, hamburgers and Chinese food, are highly
salted. Bottled mineral waters can contribute a significant amount of
sodium. An indication of sodium content is usually given on the label.
An increase in
potassium intake seems to offset the adverse effect that sodium has
on blood pressure. Foods that contain significant amounts of potassium
and also low levels of sodium are fresh and frozen fruits and vegetables.
But there is no justification for the unrestricted use of potassium
salts as substitutes for sodium, as this would present new problems.
Potassium supplements and salt substitutes can be potentially hazardous
to health and should only be used under medical supervision.
dietary intake of sodium (Australia):