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Is sourdough ‘better’ than other bread?

Maybe, says Real Bread Campaign coordinator Chris Young.

Sourdough sandwich loaf by Chris Young / CC-BY-SA 4.0

Sourdough sandwich loaf by Chris Young / CC-BY-SA 4.0

There’s a lot of myth, mystery and misunderstanding (in some cases on both sides of the bakery counter) surrounding sourdough bread, so let’s help to sift proven fact from evidence and opinion. 

Unless someone has an allergy or intolerance to baker’s yeast (Saccharomyces cerevisiae), there is nothing wrong with it. A skilled baker can make great Real Bread with baker’s yeast.

A growing number of studies, however, collectively suggest that making bread using a genuine sourdough process might have greater nutritional and other health benefits

Potential benefits

Over those many hours of slow fermentation, lactic acid bacteria (LAB) produce lactic and acetic acids (and other compounds), which research suggests might (please see the caveats below) have one or more of a number of beneficial effects: 

  • Reducing the levels of phytic acid. This is the main form in which plants (especially seeds and pulses) store phosphorus, but it combines with certain minerals including calcium, zinc, magnesium and, notably, iron in a way that makes the human body less able to absorb and make use of them.  
  • A lowering of the glycaemic index (GI) of bread, which has positive implications for managing conditions including diabetes and obesity.
  • A natural preservative effect, delaying staling and inhibiting mould growth. 
  • Improving the nutritional properties of starch. 
  • Free amino acids and gamma amino butyric acid (GABA), products of lactic acid bacteria, might increase a sourdough bread’s nutritional value. 
  • Increase in thiamine, riboflavin and pyridoxine (B vitamins) 
  • Increase in antioxidant pronyl-L-lysine, which a number of studies have suggested might have a beneficial effect in reducing colorectal cancers.
  • Reducing (but not eliminating) the production of acrylamide, a potential carcinogen that is generated in small amounts when starchy foods (such as potatoes and dough) are cooked at temperatures above 120°C. 
  • Reducing the levels of FODMAPs - fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are short-chain carbohydrates that are not easily absorbed through the lower intestine, where they attract water and ferment, triggering symptoms in people with irratable bowel syndrome. 
  • Reduction in the gliadin fractions (components of gluten) responsible for triggering the coeliac response and other negative reactions to gluten that some people experience. NB This does not make sourdough bread gluten-free or even meaningfully lower in gluten. 

Additionally, some people report that they can enjoy eating genuine sourdough bread, while they find other types of bread and/or industrial loaf products hard to stomach. 

We have published links to some of the studies we have found here.


Evidence is not proof and belief is not fact 

Whatever you have heard, read or experienced personally to be true for you, none of the above has been proven beyond doubt as general fact that applies in all (or even the majority of) cases. Also bear in mind that:

  • All studies done so far have been relatively short and small.
  • Each study had specific parameters (for example, the particular strain of lactic acid bacteria and grain being studied, the fermentation time and temperature) so its results can't necessarily be extrapolated to apply to all sourdough bread.
  • The results of in vitro studies and in vivo animal studies won't necessarily correlate with effects in human beings.

The Real Bread Campaign calls for more research to be done on the potentially beneficial effects of sourdough fermentation in order to prove (or disprove) things that such small studies have concluded, and to get a better understanding of the personal experiences that some people report.

Health and nutrition claims 

Given the growing body of evidence (perhaps including positive personal experiences that you or people you know have had) it’s understandable that a baker might feel justified in saying that their sourdough bread is ‘more digestible’ or ‘gut friendly’. They might even feel they have good reason to say that it is safe for someone with coeliac disease (or who has another medical reason for eliminating wheat or gluten from their diet) to eat sourdough.

It is not legal to do any of this in the UK or EU.  

In the EU, the use of health and nutrition claims is controlled by Regulation (EC) No 1924/2006 and all that are permitted are listed in the EU Register of Nutrition and Health Claims. Neither this or the Great Britain nutrition and health claims (NHC) register has any claims relating to sourdough bread/fermenataion or different types of wheat. See also  The Committee of Advertising Practice’s advice on making health claims in non-broadcast advertising

If you’ make and sell sourdough bread, please stay within the law and, unless you are a registered physician with the qualification, expertise and licence to practise in the relevant field, don’t give out medical advice, or anything that could be construed as such. 

Sourdough bread is not yeast free 

A sourdough culture will always contain one or more species of yeast. In some cases these yeasts might include the same species (Saccharomyces cerevisiae) that is sold as baker's and brewer's yeast, though it is likely to be genetically different to any commercially-cultivated strain. 

Concentrations of yeast in a genuine sourdough may well be lower than in bread made with commercial yeast. Yeast cells die at around 60°C and the internal temperature of bread should reach at least 90°C during baking. Some people might still have adverse reactions even to small amounts of dead yeast cells and by-products, though.  

Say no to sourfaux 

Any potential benefits of sourdough bread, such as those outlined above, rely on long fermentation in the presence of LAB. Speeding up the process, or removing live LAB from the equation altogether, reduces or eliminates the possibility of the necessary biochemical changes taking place.

The Real Bread Campaign believes that to be named or marketed using the word sourdough, bread (by the Campaign’s ‘no additives’ definition) must be: 

  1. Leavened only using a live sourdough culture, without the addition of baker’s yeast or other raising agents, such as baking powder. 
  2. Made without using other souring agents such as vinegar or inert sourdough powder/concentrate. 

Products named or marketed using the word sourdough but that fail to meet these simple criteria are what we call sourfaux and Campaign co-founder Andrew Whitley calls pseudough.

A starter culture can be used in combination with baker’s yeast to make Real Bread as it can improve the flavour, aroma and texture. Please, please don’t use the word sourdough in the name or marketing of such loaves, though! 

Since 2009 the Campaign has lobbied the UK government for an Honest Crust Act of improved loaf labelling and marketing legislation. This includes a call for the criteria above to be in the basis of a legal definition of the word sourdough. 

This is an adapted extract from the microbakery handbook Knead to Know...more, due for publication by Sustain on 1 November 2021.

Published Thursday 9 September 2021

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