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A small trial including 20 people were given either sourdough whole-grain bread or refined white bread to eat for one week. After a two-week break, each participant switched bread types for another week.

The study found very surprising results. Consuming either bread type improved cholesterol levels and improved markers of inflammation. The glycemic response was also dependent on the person’s gut microbiome composition and not bread type. This was surprising considering that fiber slows digestion and normally lowers the glycemic response. The bacterial strains that affected the glycemic response were Coprobacter fastidiosus and Lachnospiraceae bacterium, the latter of which has previously been associated with the development of type 2 diabetes.

More research needs to be done before any definitive conclusions can be made but this study just highlights the potential importance of the gut microbiome in the glycemic response to food. Here is a link to the full study.

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    Look at Europeans and white bread consumption. Italians are one of the longest living groups and there is plenty of white bread and white pasta consumed. If white bread was so bad, we should see those results in the italian and french populations.

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      I find it amazing the discussion of wheat and bread here is limited to this articleis. One could say the current state of the US type 2 diabetes epidemic can be traced to this one “food”. Yet we discuss whether white or wheat is “better” for us? The wheat lobby must be ecstatic. I would love to see a more in depth discussion of wheat and what it has become today and why vs this junk science. Ever think of getting an interview with the author of Wheat Belly? I think this article and study totally misses the point by design.

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        I think that the whole grains topic is a complicated one. I still think refined white bread is bad. One thing to keep in mind is that this study did not look at any long-term effects. Regarding gluten, it does cause the release of zonulin which transiently opens the tight junctions in the gut barrier but does not cause inflammation in people that do not have celiac or poor gut health (including dysbiosis) because the tight junctions close in a matter of minutes (they stay open in people with poor gut health). Other studies have found that whole grains are associated with lower markers of inflammation including CRP, and fibrinogen (probably reflective of people with decent gut health).

        I think the point of studies like these are that there are many factors including microbiome composition, gene polymorphisms, etc. that affect our physiological responses to food and that a more personalized nutrition approach may actually be the most optimal dietary approach. Another way to look at this would be to look at how vastly different people respond to different types of dietary fat. Some people have lower inflammatory biomarkers, triglycerides etc while others' triglycerides dramatically elevate and inflammatory biomarkers increase. It really depends on certain gene polymorphisms and intake ratios of various types of fat (listen to my short 20-minute audio podcast on does saturated fat cause heart disease on iTunes.)

        I personally do not eat bread but I do eat whole oats once in a while and I eat other grains like quinoa. They do not negatively affect my blood glucose levels or inflammatory biomarkers…but I have good gut health.

        The Composition of Bread

        For those interested in the bread composition…this is taken from the study: “Flour was freshly stone milled from hard red bread wheat (Triticum aestivum var. aestivum). The resulting flour was sifted in order to remove only the largest particles of bran, resulting in a 98% “extraction rate” (1000 g of wheat yielded 980 g of flour). Loaves were prepared using the following four ingredients: freshly stone milled flour as described above, water, salt and a mature sourdough starter without any other additive. The overall formula for the bread was (in bakers’ percentage) 100% flour, 90% water, and 1.8% salt with the sourdough starter portion representing 37% of total flour weight (i.e., 20% of the flour in the formula had been pre-fermented). The dough was kneaded in a planetary mixer, “bulk” fermented for 1 hr at 24°C and “retarded” at 4°C for 8 hr. The dough was portioned into 1150 g pieces, shaped and transferred into loaf pans, where they underwent “proofing” (final rising) for 2 hr at 24°C. The loaves were baked in a stone hearth oven at 245°C for approximately 60 min to obtain final loaf weight of 1kg after baking.”