White Bread vs Sourdough, Should Anyone Care?

Michael Pollan, best known for his book “An Omnivore’s Dilemma” produced a 2016 multi-part documentary on Netflix called “Cooked”.  A recurring theme throughout was that the global obesity crisis is tied to the changes in the way that we consume food.  His best example involved Americans moving from traditional breads, now known as sourdough, to processed breads that fill our supermarket shelves.  It’s a compelling argument, especially when he illustrates how sourdough bread is made and how that compares to today’s spongy loaves packaged in plastic sleeves that stay “fresh” for weeks.

What makes sourdough bread “sour”? The distinctive taste comes from microbes that are used when making the bread. A “starter culture” of wild yeast strains and bacteria fills the loaves with the sour taste that many people know and love. These microbes in sourdough bread have been used since ancient times, unlike industrially-made white loaves, which have been produced using yeasts that date back only 150 years.

But Does Sourdough have health benefits?

As well as its rich history, sourdough bread has been viewed as having health benefits derived from the microbes the bread contains. According to The Guardian, the microbes “slow down the rate at which glucose is released into the bloodstream.” This means that sourdough bread has a low glycemic index and is considered a good choice for anyone who is managing their blood glucose levels.

In a piece written by Ed Yong of The Atlantic, a study was highlighted that compared processed, white bread to sourdough bread and the effects it has on people’s health and nutrition. Israeli scientists Eran Segal and Eran Elinav led a team which studied the common claim that sourdough bread is overall a better option for people. But were the results what they expected?

The Study

In a small, thorough study, volunteers were monitored for a one week stint of eating either white or sourdough bread. Out of 20 volunteers, 10 were asked to spend half a week eating the white bread and the other half eating sourdough bread. The other volunteers were asked to do the same, but in reverse order. Nearly 20 variables were measured of each of the volunteers, including blood pressure, weight, blood sugar, cholesterol, and various hormones.

Results--It depends

To the scientists surprise, there was no significant difference between the two breads on any of the parameters that were collected. What surprised the scientists even more was that the results showed that people vary substantially in how the two types of bread affect their blood sugar. Some of the patient’s blood sugar spiked more dramatically when eating white bread over sourdough, however other patients results were reverse. With these results, it suggests that the common belief that sourdough has a lower glycemic index than white bread is only true for some people.

So what does this mean for the future of health and nutrition guidelines? It means that nutrition needs to be personalized for each individual patient. Instead of offering universal dietary recommendations, or categorizing foods as “healthy” or “unhealthy”, the science of nutrition should be different for each patient.

Why is this relevant for MATClinics?  Two reasons:

  1. Correlation vs Causation:  We think the Israeli study is an excellent example of science trumping intuition. Correlation, the emergence and growth in processed bread tied to the growth in global obesity, was proven not to equate to causation of societal obesity. 

  2. Individual Metabolism:  Different people metabolized the breads differently.  Who is who? Do you know whether you are better off eating Wonder Bread or your grandmother's sourdough?

In the addiction world, there are endless studies and politicians spouting about their newfound solution.  The problem, however, is that we know very little about why some people get addicted and others do not.  We know even less about why some treatments work for some people and not others.

We can safely state that opioid addiction is a thornier problem than which loaf of bread to eat, but if we can't even predict how breads impact the population, how can we possibly be so strongly convinced about what the right solution is for the opioid epidemic.

Humility in the face of such a large and intractable problem would be a welcome addition to the conversation around addiction.