Sourdough has surged in popularity around the world. Good bakeries (along with cafés and restaurants) sell like a badge of honour. Part of sourdough’s appeal is its health advantages; but why do health experts tout it as one of the most nutritious breads available?

Sourdough bread has numerous health advantages over modern yeast bread. In fact, nutritionists believe sourdough bread made with white flour is more nutritious and healthy than whole wheat bread made with dried baker’s yeast. This may seem surprising and even counter-intuitive. However, the health advantages of sourdough are due to the wide diversity and type of microorganisms (both bacteria and yeast) used to make it, versus the single species of yeast used to make modern yeast bread.

Old-style artisan sourdough bread is made with a sourdough ‘starter’ that serves as the leavening agent. This starter is essentially a thick soup of flour, water, wild bacteria and wild yeast. The bacteria and yeast in the starter are obtained by simply leaving out a flour and water mixture in a warm place over time. The wet flour attracts the wild bacteria and wild yeast species in the ambient air. Once these microorganisms find this substrate, they will begin to use it to grow and multiply.

There are literally dozens of species of lactobacillus bacteria and saccharomyces yeast species in the air that are attracted to the flour and water substrate. However, the exact species composition that end up in a starter will vary somewhat between geographic locations and climates because different bacteria and different yeast will be present in different places.

A sourdough starter created and maintained in San Francisco will have a different assemblage of bacteria and yeast species than a sourdough starter created and maintained in Texas. However, the collection of bacteria and yeasts in the different sourdough starters will also be somewhat similar because only certain types of bacteria and yeast are attracted to wet flour and can survive by eating the flour and living in this substrate. For example, you’ll get lactobacillus species of bacteria in both San Francisco and Texas but the actual species and the numbers of each species may vary. This is why a sourdough starter that is found to be particularly good will sometimes be passed down from generation to generation.

One of the primary health advantages of sourdough bread is the fact that it is loaded with beneficial probiotics. In fact, a single slice of traditionally made sourdough bread will have a much higher diversity of probiotics than almost all brands of yoghurt sold in the US. While these yogurts may have two to five species of probiotics, a slice of traditionally prepared sourdough bread will contain dozens of probiotics. Eating sourdough bread will fill your gastrointestinal system with beneficial probiotics in much the same way as eating traditionally prepared kimchi or sauerkraut would.

Probiotics allow you to more easily digest your food and obtain nutrients that would be otherwise be unavailable to you. They also help you maintain a slightly alkaline internal environment, which confers a whole cascade of health advantages.

Individuals with celiac disease or gluten sensitivity will be happy to hear you may be able to tolerate sourdough bread, as long as it is made in the traditional style. The living lactobacillus bacterial species in sourdough bread essentially pre-digest gluten. The gluten molecule is made of two proteins, gliadin and glutenin.

It is actually the gliadin part of the molecule that most people with a gluten sensitivity have a problem with. This is because their immune system recognises gliadin as a foreign substance and attacks it. However, the lactobacillus bacteria in old-style sourdough bread breaks down gliadin within four hours of fermentation. If you have coeliac disease or a gluten sensitivity, look for sourdough breads that have a stronger sour taste because these breads will have been fermented longer and will contain less gliadin.

Sourdough bread is also the best bread for diabetics to eat. The lactobacillus bacteria make the absorption of the bread a much slower process. This means old-style sourdough bread has a lower glycemic index than modern yeast breads. Foods with a lower glycemic index do not raise blood sugar as much because the glucose obtained from the breakdown of food is released more slowly into the bloodstream. For diabetics, this means they can enjoy foods that are often on the ‘avoid’ list such as pizza, bagels and sandwiches, as long as they are made with old-style sourdough bread.

Throughout the past few decades, scientists and nutritionists have discovered people who eat a lot of grains are often deficient in essential minerals such as iron, magnesium, zinc, copper, and phosphorous. This was a mystery until it was discovered that substances called phytates, found in high quantities in wheat, interferes with the absorption of these minerals in the human body. In fact, phylates are very powerful chelators, binding with these minerals and quite literally moving them out of the body before they can be absorbed.

While phytates are also found in beans, nuts, and other plants, they are more highly concentrated in wheat, especially the bran portion of the wheat. However, when sourdough bread is traditionally prepared, the lactobacillus bacterial species neutralise more than 60 per cent of these phytates. In modern yeast bread, however, these lactobacillus bacterial species are absent and, therefore, most of the phytates remain in the finished product. This means a person eating sourdough bread can obtain more nutrients out of the wheat than the remaining phytates remove. This is not so for a person who eats modern yeast bread and, thus, mineral deficiencies can set in.

It should be noted phylates are actually a double-edged sword and do confer some important health advantages as long as they are kept at low levels. They are anti-inflammatory and can help chelate toxic heavy metals out of the body. Recent research indicates they may also stop the proliferation of cancer cells. Therefore, traditionally made sourdough bread seems to offer the right balance of phylates whereas modern yeast bread puts too many phylates into the body so they end up causing more harm than good.

The next time your customers are deliberating over a loaf, recommend a good, crusty sourdough loaf – you’ll be supporting a time-honored bread-making tradition dating back more than 3000 years.