They found that, with the exception of crackers, gluten free foods contained more fat, salt and sugar and also had lower fibre and protein content than their equivalents.
A GF diet is the only treatment option for those who suffer from coeliac disease but many more people in the UK and around the world avoid gluten foods as it is perceived to contribute towards a healthy lifestyle.
Be sure to choose an authentic sourdough, as some are faux sourdough and contain yeast rather than the traditional starter.
Authentic sourdough takes a long time to produce and results in an acidic and chewy bread, two features that lower the GI.
Wholemeal bread is made from wholegrains that have been milled to a fine texture, giving a plain brown appearance.
With so many choices of bread available, it's hard to know which is best for our health.
Writing for The Conversation, Leah Dowling, lecturer in dietetics at Swinburne University of Technology, gives her take on each type.
Wholemeal flour contains more fibre than white flour.
Wholemeal bread also contains more vitamins and minerals than many white breads, but has a higher GI than wholegrain breads.