Low-salt diet may boost lung health
14 June 2005

Cutting salt levels in your diet may help to reduce the risk of exercise-induced asthma, according to a new US study.

Researchers at Indiana University found that reducing salt intake for two weeks helped to reduce symptoms and increase lung function in people whose asthma was usually triggered by doing sports and physical activity.

For the study, a group of 24 people with exercise-induced asthma was divided into two: for two weeks, one was given a low-salt diet containing 1.4g of sodium a day (sodium is the harmful component in salt); the other received food containing almost 10g of sodium each day.

Testing the participants after physical activity, the researchers found that those on the high-salt diet experienced a 27% reduction in lung function, compared to a fall of only 8% in those eating the low-sodium diet. As a drop of up to 10% in lung function following exercise is considered normal, the team concluded that the low-salt diet had all but eliminated the exercise-induced symptoms.

Timothy Mickleborough, leading the study, presented his team's research at the Annual Meeting of the American College of Sports Medicine in June 2005: 'These findings show that modifying your diet has the potential to modify a disease state,’ he said.

Recommended levels

The UK government recommends that adults eat a maximum of 6g of salt a day, which is about a level teaspoonful. For children, recommended amounts are smaller: 2g a day from 1-3 years; up to 3g a day for 4-6-year-olds and a limit of 5g a day for 7-10-year-olds.

The salt content of processed foods is indicated on the side of the packaging as 'sodium’. Generally, 0.5g of sodium per 100g is high, while 0.1g is fairly low.

In order to calculate the actual weight of the salt you are consuming, multiply the sodium content of the food you eat by 2.5. So if you eat 200g of food containing 1g per100g of sodium you have to multiply 2g by 2.5, which would total 5g of salt. the Food Standards Agency's website includes a salt calculator to help you work out your levels.

'This is a small study and little research has been done in this area that would give us conclusive evidence that dietary salt levels affect asthma symptoms,' said Josianne Roma-Reardon, Asthma UK's Senior Policy & Information Officer.

'However, we know from previous research that eating lots of fresh foods, including oily fish, fruit and vegetables, can help to reduce symptoms in some people with asthma,' she added. 'We also know that many processed foods contain high levels of salt.

'With this in mind it would make sense for people with asthma to stick to a diet of fresh foods that are likely to contain lower levels of salt,' she concluded.