Which supermarket loaf is best for gut health? As experts warn your choice of bread is a key factor in bowel cancer risk, diet gurus reveal whether a sourdough is any better than a sandwich loaf

Wholemeal, white, sourdough, seeded, multigrain; the bread aisle can be confusing and overwhelming. But if you're looking for a loaf that will support your gut health, then it's worth knowing what's what. The type of flour used, fibre content and even ingredients used during processing, can all have an impact on your gut microbiome – the collective name for the trillions of different bacteria that live within your gut.And it's not just about digestion. Experts now believe eating too much of the wrong sort of bread can even raise the risk of dying from bowel cancer. A 2025 study of more than 1,600 patients with late-stage colon cancer found that people who consumed more pro-inflammatory foods – such as white bread – were nearly 90 per cent more likely to die from the disease. 'What you eat can have a big impact on the type of bacteria that live in your gut. This bacteria can have an impact on your general digestion, immune health, your mood and even your metabolism,' says Nichola Ludlam-Raine, a dietitian and author of How Not To Eat Ultra Processed.'Fibre in particular can act as a prebiotic, feeding gut bacteria and helping them to thrive.'So, which bread is best for your gut? Read on for our expert advice on which loaves will work for you – and which are best left on the shelf. The best loaves for your gutJason's Fibre Seeded Sourdough £2.80 Per slice: 123 calories, 0.2g saturated fat, 5.4g protein, 5.1g fibre, 0.41g salt, 1.7g sugar With 5.1g of fibre per slice, this seeded sourdough provides an impressive 17 percent of the recommended daily intake for adultsWith 5.1g of fibre per slice, this seeded sourdough provides an impressive 17 per cent of the recommended daily fibre intake for adults.According to the British Nutrition Foundation and the UK Scientific Advisory Committee on Nutrition (SACN), British adults should be consuming a minimum of 30g of fibre per day.Most of us currently consume far below this, however – averaging around 20g or less, which can lead to digestive issues including constipation.'This loaf also contains a mixture of seeds and grains, alongside added oat fibre,' says Kirsten Jackson, consultant dietitian and founder of The Irritable Bowel Syndrome (IBS) Dietitian.'Having different sources of fibre in our diet is beneficial because different fibres have different effects on bowel function and our gut bacteria.'Plus, as a sourdough bread, this loaf may also provide other beneficial effects for your gut.Sourdough bread is bread that rises using a natural, living mixture of wild yeast and good bacteria, known as a 'starter', instead of store-bought commercial yeast.Waitrose No1 3 Seed Sourdough £2.25Per slice: 128 calories, 0.3g saturated fat, 4.8g protein, 3.5g fibre, 0.47g salt, 1.3g sugarThis bread contains a mixture of seeds and grains, including rye, oats and wheat - which all contribute to its gut-loving 3.5g of fibre per sliceThis bread contains a mixture of seeds and grains, including rye, oats and wheat – which all contribute to its gut-loving 3.5g of fibre per slice.'Having a variety of plant foods in the diet is beneficial for gut health because different fibres can have different effects on our gut bacteria,' says Ms Jackson.'However, the main ingredient is still refined wheat flour, so I wouldn't automatically consider it superior to a wholemeal loaf.'One common misconception, says Ms Jackson, is that sourdough is always easier to digest. Traditional sourdough fermentation can reduce fructans, which are fermentable carbohydrates commonly found in bread, that can trigger symptoms such as bloating, gas, indigestion, constipation or diarrhoea in people with IBS.During the fermentation process, the live bacteria from the sourdough starter produce enzymes that actively break down fructans. But this process depends heavily on the ingredients in the bread, and how long it's left to ferment, says Ms Jackson. 'We can't assume that every supermarket sourdough will have the same effect, or that it will necessarily be better tolerated by someone with IBS.'Tesco Hi Fibre Seed Loaf£1.55 Per slice: 162 calories, 0.8g saturated fat, 6.7g protein, 3.8g fibre, 0.42g salt, 1.1g sugar The seeds in this loaf are a useful addition to bread because they provide fibre, unsaturated fats and a range of micronutrients such as magnesium and zinc, says Ms JacksonTesco's Hi Fibre Seed Loaf is another good, gut-healthy option, says Ms Jackson – providing 3.8g of fibre per slice, which makes a useful contribution towards the recommended 30g per day. The seeds in this loaf provide fibre, unsaturated fats and a range of micronutrients such as magnesium and zinc.Research has found that magnesium deficiency could reduce the diversity of gut bacteria.'This bread is slightly higher in calories and fat than some of the other options, but much of the fat in seeded breads comes from the seeds themselves, which contain beneficial unsaturated fats,' says Ms Jackson.'I would also encourage people to look beyond the 'high fibre' label and check the ingredients. A product can be high in fibre without necessarily being predominantly made from wholegrains.'Likewise, she says, check that fibre isn't simply added, rather than coming from the wholegrains themselves. Ingredients such as inulin, chicory root fibre, oat fibre or isolated wheat fibre – often found on lengthy ingredient lists – add fibre but lack the naturally occurring vitamins and minerals contained in wholegrains.Hovis Seed Sensations Original £2Per slice: 122 calories, 0.3g saturated fat, 4.4g protein, 2.3g fibre, 0.39g salt, 1.7g sugar Despite the fact that this bread contains an impressive seven different types of seeds, it actually provides less fibre per slice than some of the other seeded optionsDespite the fact that this bread contains an impressive seven different types of seeds, it actually provides less fibre per slice than some of the other seeded options, says Ms Jackson.'We shouldn't automatically assume that seeded bread is particularly high in fibre,' she explains.'The main ingredient is refined wheat flour rather than wholemeal flour, meaning some of the naturally occurring fibre from the grain has been removed.'Hovis Best of Both Thick Bread£1.15Per slice: 113 calories, 0.1g saturated fat, 4.7g protein, 2.8g fibre, 0.45g salt, 1.4g sugarWhen you want your family to enjoy the taste of soft, white bread, but reap some of the goodness of wholemeal, a Best of Both loaf can help.'This is a useful middle ground if you want more fibre than white bread. It combines wholemeal and white wheat flour and provides 2.8g fibre per slice,' says Ms Ludlam-Raine.This Hovis does also contain additives however, including E282 – a preservative -and E471 and E472e, which are emulsifiers, to help with freshness and texture.Warburtons Wholemeal95pPer slice: 55 calories, 0.1g saturated fat, 2.5g protein, 1.5g fibre, 0.23g salt, 0.6g sugar For a budget-friendly, everyday loaf, make this your go-to, says Ms JacksonFor a budget-friendly, everyday loaf, make this your go-to.'This is actually one of my favourite options in the comparison because it demonstrates that you don't need to spend a fortune on expensive artisan breads to support your gut health,' says Ms Jackson.'Although 1.5g of fibre per slice might initially sound relatively low, these slices are considerably smaller than some of the others. When you compare the breads per 100g, the fibre content is actually very respectable.'Wholemeal flour is the main ingredient in this loaf, meaning the bread retains more of the naturally occurring fibre and nutrients found in the whole grain.'Wholegrains are associated with a range of health benefits, including supporting bowel regularity and reducing the risk of certain chronic diseases such as cardiovascular disease and type 2 diabetes,' adds Ms Jackson.A potential drawback, however, is the emulsifier sodium stearoyl lactylate (E481) used to extend the shelf life of the loaf.In a study published in the journal Frontiers In Microbiology, E481 was shown to potentially cause negative changes to the gut microbiome, which could in turn have a negative impact on gut health.'However, this hasn't been shown to cause harm in people eating bread containing E481, and we don't know whether the quantities used in this product would have any meaningful effect,' adds Ms Jackson.The worst offenders for your gutSainsbury's Soft Medium Sliced White Bread74pPer slice: 97 calories, 0.2g saturated fat, 3.2g protein, 0.8g fibre, 0.32g salt, 1.4g sugar Nutritionally, says Ms Ludlam Raine, this loaf won't have much to offer youWhile white bread isn't inherently bad for your gut, it certainly won't support it. Nutritionally, says Ms Ludlam Raine, this loaf won't have much to offer you. But if you love a sliced white bread, you can up its fibre content with toppings, she adds – such as peanut butter, berries and seeds. Waitrose Sliced Brioche Loaf £3.20Per slice: 98 calories, 1.7g saturated fat, 2.45g protein, 0.5g fibre, 0.3g salt, 3.3g sugarOne of the top ingredients in brioche, sugar has been shown to negatively disrupt the gut microbiome.But it's the low fibre content of this loaf that's the bigger gut problem.'With 1g per two slices, it won't add as much to your daily fibre intake,' warns Ms Ludlam-Raine.She recommends serving your brioche with nut butter and fruit or alongside other higher-fibre foods such as avocado with eggs, to bump up the fibre.Warburtons Tiger Bloomer with Sourdough £1.95Per slice: 96 calories, 0.1g saturated fat, 4.1g protein, 0.7g fibre, 0.34g salt, 1.1g sugar If it's fibre you're trying to increase, this loaf is likely your worst optionIf you're trying to increase your fibre intake, this loaf is likely your worst option.'At just 0.7g per slice, it contributes relatively little towards the recommended daily intake of 30g,' says Ms Jackson.'The main ingredient is refined wheat flour, and although the bread contains sourdough, this accounts for just 3 percent of the ingredients. 'So, it's a useful reminder that a bread containing sourdough isn't necessarily the same as a traditionally fermented sourdough, and we can't assume it provides the same potential digestive benefits.'