Is sourdough bread really healthier?
And do the health benefits justify the time investment?
My baby, just out of the oven
My sourdough starter is part of my home. Like a pet, it needs attention – a morning and evening feed. It's actually the only pet I want, as it asks for so very little, yet like all those beloved dogs and cats, gives back so much more than it receives.
Feeding my starter has become a part of my daily routine in the past few months, as has been the baking of the daily loaf. When I make too many I give them away, sometimes with an offer of a jar of the starter – or leaven – the magic behind the sourdough.
My starter is indeed some kind of reflection of my home, as it contains the unique microorganisms that live here. No two starters are alike, even if they started from the same batch, or came from your favorite bakery, and today’s starter is different from the one you’ll have next month. It took me around two weeks to get from whole wheat flour and water to a reliable starter, but now my baby’s strong, resilient, and as long as it’s fed, it will make delicious, nourishing bread.
A long history
A sourdough bread is made out of four ingredients: flour, water, salt and the starter. Seemingly simple ingredients, except the starter. Many bakers name theirs and speak of them in terms of endearment – sourdough starter is no ordinary ingredient.
The starter is a complex microbial ecosystem, consisting mostly of lactic acid bacteria and yeast. These microbes ferment the dough, give it its unique flavor characteristics, and change the bread’s nutritional profile.
Fermentation must have started as a happy accident thousands of years ago.
In order to digest dry cereal ancient people had to process it: grind the hard grain, and mix it with water. At some point they must have noticed the pleasant sour aroma from the left-on-its-own porridge, and the accompanying airy quality it took, and when they heated this puffed up sponge it rose even more, like magic, emitting the most magnificent scent.
The rest is history. Sourdough was already part of the European diet 5000 years ago; murals of baking leavened dough in Egypt date back to 1500 BC. Sourdough was how bread was leavened up until the 19th century, when it was largely replaced by baker’s yeast, Saccharomyces cerevisiae, a monoculture of yeast that gives predictable results. Nowadays, sourdough starter is used mainly in artisan breads.
What’s in that starter?
Each starter is unique, and because it’s a living culture of organisms (which produce their next generation several times an hour), it evolves constantly. The dominant bacteria are Lactobacillus species, bacteria that produce lactic acid, which vary from region to region. The typical San Francisco environment has native inhabitants that are distinct from those in Rome. Lactobacillus sanfranciscensis, a common species of lactic acid producing bacteria is named after San Francisco, where it was first identified in this city’s famous sourdough, but it’s by no means endemic to the Bay area.
Yeasts are less abundant: There are generally 100 bacteria to each yeast. Many different kinds of yeast are typically present in sourdough starter, and those, too, depend on variables such as where the leaven originated, the type of grain used, humidity, and temperature. The yeast and the bacteria are everywhere, in the air and in flour; by nurturing your starter you’re giving them an opportunity to form a colony and collaborate in bread making.
No wonder homemade sourdough bread holds so many surprises.
Professional bakeries go to great lengths to get a consistent loaf, but for the home baker the endless mystery of the sourdough experiment may be part of the appeal – you can nurture your starter, but total control isn’t possible, and serendipity is part of the game.
During the sourdough’s long fermentation, typically 12-24 hours, the microorganisms extract energy from the carbs in the dough, and develop flavor molecules – mainly organic acids, alcohols, esters, and carbonyls – through that process. The yeast in the starter is responsible for most of the rise of the bread, and this negative space, created by the gasses that the microorganisms emit, is as important as its substance. A perfect sourdough inner texture will have holes both big and small, alveoli in baker speak.
Sourdough’s airiness: holes of different sizes, derived from fermentation
Is sourdough healthier?
Sourdough’s flavor and mouthfeel are its main selling points – devotees swear it’s the best bread with no parallels – and it’s a more natural and traditional loaf.
But is it nutritionally superior to other breads?
The long fermentation process is one in which the microbial culture changes and digests the dough, hydrolysing proteins, using up sugars, and chemically transforming an amorphous blob into a plump crusted loaf.
During fermentation, sourdough bacteria and yeast produce bioactive peptides, which are fragments of protein made of 3-20 amino acids with antioxidant and anti-inflammatory activity, at least in the test tube. These peptides remain active after baking, and may promote health. Lunasin, for instance, is a strong anti-tumoral peptide that's produced during sourdough fermentation.
Sourdough, as the name suggests, is sour, acidic. The bacteria’s produce lactic acid, as well as bacteriocins and antifungals, which act as biopreservatives, protecting the bread from spoilage microbes. That’s why sourdough keeps so well despite having no added preservatives.
Phytic acid, or phytate, a substance found in cereal grains, is considered anti-nutritional: it interferes with absorption of grain’s minerals such as iron, magnesium, potassium and zinc. The enzyme, phytase, present in flour, breaks down phytic acid, making these minerals bioavailable, but this enzyme is usually quite inactive. The acidity of sourdough, as well as the phytase made by the culture, degrade phytate significantly, therefore increasing the bioavailability of the hidden micronutrients.
The friendly bacteria in sourdough don’t survive the high temperatures of the oven, therefore sourdough is not a probiotic. It’s a prebiotic though – the fiber and absence of additives may benefit a healthy microbiome.
My sourdough starter
Sourdough may also provide relief for those of us who have specific sensitivities and conditions.
Let’s start with gluten. Sourdough may be better tolerated by people with gluten sensitivity. Sourdough fermentation results in some breakdown of gluten, especially the gliadin component of gluten, and wheat flour sourdough may be better tolerated by people sensitive to gluten. Wheat sourdough isn’t gluten free, though, and people with celiac should avoid it.
Bread is also a thorny issue for people with diabetes, insulin resistance, and people on a low glycemic diet. Sourdough bread, however, typically has a lower glycemic index than regular bread – 54, which puts it in the low glycemic index food category – and it may elicit lower spikes in blood sugar and insulin, making it more suitable for people with glucose intolerance (regular breads have a glycemic index in the 70s).
Each sourdough bread is of course different. Sourdough can be made with whole or refined flour, with wheat and with rye and many other grains; the more whole grains in the dough, the healthier the bread.
Worth the trouble?
A sourdough routine has been somewhat popular in these crazy Covid-19 times for many reasons. Once you look at a sourdough recipe you’ll realize the time and space commitments, and that sourdough bread making is more logically outsourced. Even in old times bread was at least baked in a central location – I feel kind of bad about heating my oven to 500 °F daily for just one or two loaves. It’s more of a hobby than a practical practice.
I strongly believe in healthy homemade meals – those needn't be complicated, or terribly time consuming, and they’re key to taking charge of your health and wellbeing.
Look at sourdough as a metaphor. When you go through the exercise of telling this bread apart from factory-made fast loaves, you see the nutritional sacrifice on the one hand, and the time saving on the other. Bread making is perhaps best left to the specialists, or those with ample time and enthusiasm to pursue the project. This is not so with something like a salad, which you can make in minutes, with incredible results.
Dr. Ayala
“I strongly believe in healthy homemade meals – those needn’t be complicated, or terribly time consuming, and they’re key to taking charge of your health and wellbeing.
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