The recommended daily intake for UK adults is a maximum of 6g, with the current average standing at 8.1g a day.
Bread is the biggest contributor of dietary salt in the UK, providing almost a fifth of the total derived from processed foods.
The researchers, led by Professor Graham MacGregor of Queen Mary University of London, analysed the salt content of various brands of packaged bread on sale in UK supermarkets during a 10 year period. Salt levels in 40 products were checked in 2001, 138 products in 2006 and 203 in 2011.
A core selection of 18 products were checked in all three years - 10 of them white bread and eight wholemeal. The main findings were that:
In 2001, the average salt level across all packaged bread products was 1.23 g per 100g
By 2006 salt levels had fallen to 1.05 g per 100g
By 2011 this had fallen further to 0.98 g per 100g
This was equivalent to a reduction in salt levels of around 20% over the decade.
The salt content of the core 18 products fell by 17%.
Overall, the number of products meeting the Department of Health’s 2012 target - of less than or equal to 1g of salt per 100g - rose from under a third (28%) in 2001 to almost three quarters (71%) in 2011.
The researchers found wide variations in salt contents between similar types of bread and between the supermarkets' own-label bread and branded products. In 2001, 38% of supermarket own-label loaves met the 2012 target compared with just 17% of branded products. By 2011, the equivalent figures were 89% and 42%, respectively.
Little difference in salt content was found between white, wholemeal and brown loaves "despite the common perception that wholemeal and brown bread are healthier alternatives to white bread," the authors say.
The variations in levels underline the need to lower salt levels in bread in the future. "This requires further progressive lower targets to be set, so that the UK can continue to lead the world in salt reduction and save the maximum number of lives," they write. They say the key to success is a gradual reduction so that consumers get used to accepting lower levels of salt in bread over time.
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