How does Sourdough particularly help support the gut microbiome?

digestion poster in sourdough school — I think it is fair to say that, the collective evidence from the studies showing increased levels of fibre and levels increased bioavailability of polyphenols, contributes to supporting our gut microbiome.

I wrote a feature recently on polyphenols and sourdough. The evidence suggests that the long slow fermentation increases bioavailability of these beneficial antioxidants .. which in turn is good for our gut microbes, and protecting against a range of diseases.. but it got me thinking about the other benefits of long slow fermentation in relation to our gut microbiome, and I thought it might be a good idea to summarise the main points. Although large-scale clinical trials on the effects of sourdough baked products on health and nutrition in humans are limited, the information so far still seems valuable. Examples include, fermentation and acid production by lactic acid bacteria and yeast have been shown to bring about improved mineral and polyphenol bioavailability – especially in those made with wholegrain flour. Sourdough baking is also consistently shown to deliver breads with higher levels of resistant starches and the lactic acid bacteria fermentation increasing the overall fibre content of sourdough breads. Sourdough can help increase your dietary fibre intake by 10-15% and the ratio of soluble to insoluble fibre can be manipulated depending on how long you ferment your dough. Recent advances in the area of gut health has shown that phenolic compounds { LINK } in addition to fibre has been shown to improve gut microbial diversity which is pivotal in maintaining a healthy gut microbiome.

In addition to polyphenols, ( a source of food for our gut microbes) sourdough breads made with wholemeal flour also provide fibre which is beneficial in prevention and management of constipation and is of importance in the management of other large-intestinal diseases such as irritable bowel syndrome and bowel cancer. There is over 50 years of research documenting how fibre consumption has been linked to body weight reduction and maintenance, and there is a mountain of evidence that supports the fact that getting enough dietary fibre helps contribute to reduced risk of an array of diseases including type 2 diabetes.

In sourdough however there is another level of benefit as the dough ferments. The lactic acid bacteria produce extracellular polysaccharides called exopolysaccharides, which could also act as a source of fibre for our gut microbiota.

I think it is fair to say that, the collective evidence from the studies showing increased levels of fibre and levels increased bioavailability of polyphenols, contributes to supporting our gut microbiome.

All reasonable care is taken when writing about health aspects of bread, but the information it contains is not intended to take the place of treatment by a qualified medical practitioner. You must seek professional advice if you are in any doubt about any medical condition. Any application of the ideas and information contained on this website is at the reader's sole discretion and risk.

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About Dr Vanessa Kimbell

Dr Vanessa Kimbell is acknowledged as one of the world’s foremost authorities on bread and human health — the first person to hold a doctorate in Baking as Lifestyle Medicine and Preventative Healthcare, and the pioneer who, long before gut health became a mainstream concern, first identified the crucial role bread plays in the gut microbiome and mental wellbeing. A fourth-generation baker of Italian descent, she has been baking sourdough since the age of 11, served her traditional apprenticeship in the Dordogne, and is a time-served, French-trained qualified baker who has worked alongside some of the world’s greatest bakers including Richard Hart and Gabriele Bonci. She has spent four decades asking the questions the food industry preferred no one asked: why was industrial mono bread slowly harming us, and what would it take to make bread that genuinely nourishes?

The answer became her life’s work. As founder and Course Director of The Sourdough School in Northamptonshire — a world-renowned centre of research and education — she has taught bakers from over 84 countries, integrated the BALM (Baking as Lifestyle Medicine) Protocol into NHS clinical practice at Bethlem Royal Hospital, and developed Proven Bread: the first bread built on clinical evidence, personalised to the individual through nutrigenetics and gut microbiome assessment. She delivered the Royal College of General Practitioners‘ approved course in the Nutrition of Bread, has been a regular contributor to BBC Radio 4’s Food Programme for many years, and collaborates with leading scientists and clinicians including Professor Tim Spector — who credits her with teaching people to make the healthiest bread in the world — and Professor David Veale. Named the Sourdough Queen by The Telegraph in 2013, her influence reaches far beyond the classroom — from artisan bakers and healthcare professionals to the world’s leading food scientists and multinational food corporations.

A bestselling international author of five books, her sixth — Proven — publishes in November 2026.

More information about Vanessa can be found at
The Sourdough School,
The Sourdough Club,
on Instagram at @SourdoughClub,
@SourdoughSchool and
@vanessakimbell,
on Facebook and
LinkedIn.