Average salt content in supermarket packaged bread has fallen by 20% over the last decade - but this reduction masks a sharp contrast between own-label and branded products, according to new research.
Salt levels in packaged bread in supermarkets across the UK fell around 20% from 1.23g per 100g in 2001, to 1.05g per 100g in 2006 and then 0.98g per 100g in 2011, according to findings published in the online journal BMJ Open.
Researchers examined 40 products in 2001, 138 in 2006 and then 203 in 2011 for the study by the Wolfson Institute of Preventive Medicine in London.
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.
But wide variations in salt content persist in similar products, and between supermarket own-label and branded products, the results showed.
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, the study found.
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 said.
Bread is the biggest contributor of dietary salt in the UK, providing almost a fifth of the total derived from processed food.
The recommended daily intake for UK adults is a maximum of 6g, with the current average 8.1g a day.
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The authors noted: "This study shows that the salt content of bread has been progressively reduced over time, contributing to the evidence base that a target-based approach to salt reduction can lead to reductions being made.
"A wide variation in salt levels was found, with many products already meeting the 2012 targets, indicating that further reductions can be made.
"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."
Professor Graham MacGregor, chairman of Consensus Action on Salt and Health (CASH), and professor of cardiovascular medicine at the Wolfson Institute, said: "A reduction in population salt intake is one of the most cost-effective measures to improve public health, as lowering salt intake lowers blood pressure and reduces the number of people suffering and dying from strokes, heart attacks and heart failure.
"Bread is the single biggest contributor of salt to the UK diet and it is vital that we set challenging targets for the bread industry in order to save the maximum number of lives."
A Department of Health spokesman said: "Too much salt can lead to high blood pressure, heart disease and stroke. So we are really pleased that there has been a 20 per cent reduction in the amount of salt in bread and are continuing to work with industry, through the Responsibility Deal, to help people reduce their salt intake.
"Many foods contain higher levels of salt than we might expect so it's important to check the label.
"To make it easy for everyone to keep track of what they eat and make healthier choices, we will soon be announcing a simple and clear system for front-of-pack labelling that everyone can use to help people make healthier choices."