Extra salt is needed during hot weather

This is not generally true. Human beings can survive on as little as one gram of salt (sodium chloride) each day, equivalent to about 20 millimoles of sodium (a millimole is another way of expressing an amount of sodium or other mineral. It provides a useful way of being able to compare the biological equivalence of different minerals - for example a millimole of sodium is equivalent to a millimole of potassium, or chloride).

In a tropical country like Papua New Guinea it is common to have an intake of the equivalent of three grams of sodium chloride. People who move from a temperate to a hot climate may find that their bodies' salt-retaining mechanisms undergo a short period of adjustment. The body has special hormones to help retain sodium.

It is common for Australian adults to consume 8 to 12 grams of salt per day (about 160 to 240 millimoles sodium). The National Health and Medical Research Council (NH&MRC) of Australia recommends that we have between 2 and 5 grams (40 and 100 millimoles) per day. Most Australians should therefore reduce their salt intake. We should not require salt even as the seasons change and the weather becomes hot.

There has been concern whether extra sodium might be required in extremely hot work environments that lead to profuse sweating (and associated sodium loss), for example, the pot room of an aluminium smelter. However, hormones in the body can regulate the amount of sodium in sweat, causing it to fall as the rate of sweating increases. Special circumstances like this probably deserve special consideration, but supplementary salt tablets will not necessarily be required, even in extreme environmental circumstances.

We are concerned these days about the adverse effects of sodium on health, especially its effects on the development of high blood pressure and osteoporosis. Most people are now aware that many commonly consumed foods such as bread, butter, margarine, and tomato sauce contain added sodium or salt, and have changed to reduced sodium varieties.