Despite a distinct lack of scientific proof, the start of the 21st century has seen a continuation of the claim that sliced supermarket bread made by the Chorleywood Bread Process (CBP)** causes bloating. A new report published by the British Nutrition Foundation in the journal Nutrition Bulletin reviews the science behind this common claim and confirms that, to date, there is no evidence to support claims that CBP bread affects the gastrointestinal system in a different way to other bread making processes.

Dr Elisabeth Weichselbaum, author of the report, says “For the average healthy consumer, there is no evidence that regular consumption of bread causes bloating or gastrointestinal discomfort, or that the way in which bread is produced, by modern or traditional methods, leads to different effects on the gastrointestinal system.”

“Bread is an important source of dietary fibre. Some people who eat little fibre and suddenly increase their intake in line with recommendations can experience abdominal discomfort, particularly when they don’t drink enough non-alcoholic fluids and are fairly inactive, but these symptoms usually disappear after a while as the body gets used to higher amounts of fibre. An alternative misconception could have arisen among those people with low fibre intakes who frequently suffer from constipation which is often perceived as being bloated. Dietary recommendations encourage a high fibre intake because of its important role in bowel health and other health benefits and most people in the UK would benefit from increasing their fibre intake.

Many consumers are not aware that four slices of wholemeal provides approximately 10g fibre (around 55% of the daily requirement); four slices of brown bread gives 7g of fibre (38% of the daily requirement); and four slices of white gives 3.2g of fibre (about 18% of the daily requirement); and may be unnecessarily avoiding bread due to their misconceptions about bloating.


Dr Weichselbaum explains that for sufferers of Irritable Bowel Syndrome (IBS) there is evidence to show that fibre in wholemeal bread may actually help relieve IBS symptoms for some people by shortening digestive transit time and conversely, that eating white bread, which has a lower bran and thus a lower insoluble fibre level, can help reduce the effects of diarrhoea-predominant IBS for others.


In the Noughties, it became almost fashionable to parade a so-called food allergy or intolerance leading to many people without a medically diagnosed allergy unnecessarily avoiding certain food groups like wheat or dairy. Dr Weichselbaum continues, “As with other forms of allergy, the proportion of people who perceive they are allergic to wheat is clearly higher than the actual prevalence of wheat allergy. If a wheat allergy is suspected, diagnosis should be made via standardised tests and unnecessary wheat avoidance may lead to inadequate intakes of key nutrients.”

In 2010 a report by the University of Portsmouth discovered too many people are self-diagnosing food allergies and could be restricting their diet unnecessarily. This research showed that up to 20 per cent of adults think they suffer from a food allergy or food intolerance. However evidence suggested that the real prevalence of food allergy and intolerance in adults was in fact less than 2 per cent. It means that millions of people could be avoiding nutritious foods unnecessarily and without proper medical advice.

The report by the University of Portsmouth also reveals that over half of the British population believes that wheat allergy is a common illness and in 2009 wheat was the most commonly self reported food allergen for both men and women. Those living alone and those aged 35-44 were most likely to report such an allergy or intolerance. But the report highlighted that confirmed wheat allergy is less common than other food allergies such as peanuts and other nuts, eggs and milk.


Bread made with the CBP is not less nutritious than bread made with more traditional bread making processes.  Investigations by Campden BRI in 2008 and 2011 found that the vitamin content of bread baked using the Chorleywood Bread Process is very similar to bread baked using more traditional methods and that this applies to white and wholemeal bread.  It is not widely recognised that bread is an important source of nutrients as well as fibre in the UK diet. “The type of flour used and the addition of nutrients to restore those lost during milling (a legal requirement in the UK but not in all other countries) has the most significant impact on the total nutrient content of bread” explains Dr Weichselbaum.


Myths about bread and bloating include a focus on yeast which by its very nature normally causes things to rise and therefore creates a mental image of bloating. Higher levels of initial yeast addition required for shorter fermentation processes such as the CBP have also been blamed by some for the modern concern about bloating.

However, it is not only the amount of yeast that is added to the dough at the start of the bread making process that determines the total amount of yeast in the final dough, but also the fermentation time. During fermentation the yeast multiplies and therefore longer fermentation time will lead to increased yeast levels in the dough, meaning that the overall level is similar to that in a shorter fermentation process. Furthermore, the yeast in bread is deactivated during baking and therefore, no matter what bread making process is used, no live yeast will be present. “We looked at whether yeast in bread is associated with symptoms of bloating, but found no published evidence to support this.” says Dr Weichselbaum.


Coeliac Disease (CD) is a chronic systemic autoimmune disorder induced by the gluten in wheat, barley and rye which is thought to be under-diagnosed in countries such as the UK. CD sufferers experience gastrointestinal symptoms including bloating and constipation. Some studies suggest that bread made with sourdough may increase tolerance of gluten in people suffering from CD. However, according to Coeliac UK (, there is insufficient evidence to recommend that coeliac patients can tolerate sourdough bread without experiencing symptoms. Therefore, it is irresponsible to suggest that bread made from sourdough is suitable for CD sufferers.

Dr Weichselbaum says, “There are no published studies comparing longer fermentation with baker’s yeast with shorter fermentation on symptoms in CD sufferers. However, even if longer fermentation with baker’s yeast was associated with a higher degree of gluten degradation, it is unlikely that the amount of gluten would be reduced to a level that is tolerated by most CD sufferers. Therefore, it is unlikely that length of fermentation using bakers’ yeast increases tolerance of bread in CD patients.”

Alex Waugh, Director at the Flour Advisory Bureau says: “Even though nine million loaves of sliced bread are eaten daily in the UK, making a positive contribution to our good health as a nation, misconceptions still persist about the nutritional value of sliced bread. That’s why we commissioned this independent report to understand the science before reaching out to consumers to address their concerns.”

“Sliced bread has been a part of our lives for over 50 years, and the sandwich for 250 years, and according to research, 57% of us believe the CBP process should be celebrated as an iconic invention, alongside the likes of the internet, space travel and the mobile phone.”

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