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Research Brief: Sourdough Rye Bread

My own recent attempts at making sourdough bread at home involves a small amount of rye flour. Rye flour contains lots of the wild yeasts and lactic acid forming bacteria needed to establish a vigorous sourdough starter.

My own recent attempts at making sourdough bread at home involves a small amount of rye flour. Rye flour contains lots of the wild yeasts and lactic acid forming bacteria needed to establish a vigorous sourdough starter.

Rye is a high FODMAP grain. While authentically prepared, slow-fermentation sourdough bread made from wheat and spelt are low in FODMAPs, sourdough rye breads tested so far in the FODMAP lab at Monash University are high in FODMAPs. But there may yet be hope for sourdough rye bread lovers.

Rationale for the Study

A recent study carried out in Finland by Dr. Reijo Laatikainen and colleagues looked at the the impact of low FODMAP rye bread on IBS symptoms. Why Finland? Rye is the most important source of dietary fiber in the diets of adults in Finland. With all of the interest in low FODMAP diets for IBS today, tolerability of rye bread is an important concern in Northern Europe. People in many other countries enjoy rye bread, too! Study citationLaatikainen R et al. Randomised clinical trial: low-FODMAP rye bread vs. regular rye bread to relieve the symptoms of irritable bowel syndrome. Aliment Pharmacol Ther. 2016;44(5):460-470. doi:10.1111/apt.13726.

Study Design and Methods

Eighty-seven participants with IBS took part in this randomized double blind controlled crossover study. This is a strong type of study design in which each patient alternately ate one of the two types of bread for 4 weeks, along with their regular diets, with a 4 week break in between. They kept track of their IBS symptoms throughout, and quality of life was monitored. Intestinal gas production was measured with hydrogen breath tests.

In this study, a "specific sourdough system" was used to make rye bread with a clearly lower FODMAP content than regular Finnish sourdough rye bread. I met Dr. Laatikainen at Digestive Disease Week in May, 2016, where he presented a poster about this research. He told me that this bread was supplied by a commercial bakery which did not divulge or publish the details of production.

Results in a Nutshell

On its own, switching from regular sourdough rye bread to the special low-FODMAP rye bread did not improve IBS symptoms or quality of life overall. However, there was significant improvement reported by study subjects in specific IBS symptoms, including flatulence, abdominal pain, cramps and stomach rumbling. Less intestinal gas was produced by subjects consuming the low-FODMAP bread. Subjects increased their intake a dietary fiber (a good thing!) on both types of sourdough rye bread.

Bottom Line

Eventually, try it!

Unless a particular brand of sourdough rye bread has been certified low-FODMAP by laboratory analysis, it should be avoided during the elimination phase of a low-FODMAP diet. However, there may be a place for it in your diet eventually, depending on your ability to tolerate oligosaccharides, the type of FODMAP in rye, and the bread-making process used by your local bakery. Bread produced by one bakery may have more or less FODMAPs than that produced by another, so try several before drawing a conclusion about sourdough rye bread. 

Its also worth noting that rye grown in one country might have a different FODMAP content than rye grown in another country. Different cultivars of rye might be grown due to differences in climate, and growing conditions are likely to be quite different from one country to the other.