Can Eating Sourdough Boost Your Immune System?

Can Eating Sourdough Boost Your Immune System?

Last week I wrote about how much of the commercial bread we eat leaves our bodies starving for nutrition.  Since then, in my mind, there has been an intersection of those findings and how this might affect our immune systems. Especially after reading this NPR Report: “Sourdough Hands: How Bakers And Bread Are A Microbial Match. ”

Surely some of that beneficial bacteria make its way into the baker’s systems. In fact,  Rob Dunn stated in the report that as bakers: “Not only do we impact the species in our food, but the species in our food impacts the species on or in our bodies.”1

Most of you already know that most common sourdough starters are packed with lactobacillus bacteria and saccharomyces yeasts, and all their related species. The NPR report explained,  “If we look at the average human hand, those bacteria and those yeasts are really quite rare—three percent maximum of fungi on the hands.

“On the bakers, they were in some cases up to 60 percent of the bacteria in particular on the hands. Which is to say that the hands looked more like sourdough in terms of the microbes they had more than they looked like the hands of the plumber or the professor.”2

According to , who wrote, in Focus Newsletter that Lactobacilli are potent immune regulators. He wrote, “Our gut microbiota have a powerful ability to prime immune regulation. From the moment we’re born, our immune system is regulated by our flora… Diet directly influences the diversity of the microbiota. Host-microbe cross-talk is key to maintaining immune tolerance and effectiveness.“3

As we face a potential pandemic from the Coronavirus, or even this year’s strain of flu, I would like to know if making sourdough bread might strengthen our immune systems?

Nutrition and Our Immune Systems

In his book, Modern Health and Disease, Dr. Maurice E. Shils, writes: “The alimentary tract houses a major portion of the body’s immune system and is directed toward defending [us] against bacterial, viral, parasitic and food antigens …The immune system requires nutrients to produce and distribute normal healthy immune cells throughout the body, to combat invasive pathogenic organisms. …deficiency in any nutrient will result in impairment of [the] immune response. Furthermore, replenishing nutrient levels to normal physiological levels will, for the most part, restore appropriate immune function.”4

According to the USDA, the nutritional breakdown for a normal 100 g slice of sourdough bread has:

  • Calories: 246 kcal
  • Fat: 0 g (and no saturated fats)
  • Carbohydrates: 51 g
  • Sodium: 561 mg
  • Fiber: 3.5 g
  • Sugar: 1.75 g (and no added sugars)
  • Protein: 8.75 g 
  • Iron: 1.26 g

However, when whole-wheat is used in sourdough, the long fermentation process delivers a powerhouse of nutrition. Researchers in the Department of Applied Nutrition and Food Chemistry at the University of Lund in Sweden found that: “when subjects consumed the bread baked with sourdough, lactic acid, and Na-propionate, their glucose, and insulin responses were reduced compared with the wholemeal bread alone.”

Vitamin and Mineral-Rich

Whole-grain sourdough is a great source of iron and selenium. Iron is important in the production of red blood cells and energy metabolism. Selenium helps our immune systems, works properly, as well as helping to prevent damage to cells and tissues. Sourdough is also a good source of B vitamins, aiding nervous system functions and helps to regulate our metabolisms.


The Things We Add to Bread

If wheat, and bread made from it, is the “staff of life” that is in our long past. Once we began refining flour, bakers discovered lighter, better results, or so they thought. 

Ed Wood in Classic Sourdoughs warned:

“Within just the last hundred years, there have been monumental changes to what we call bread, and these changes are mostly for the worse. …the baking industry adds a plethora of chemicals to flour and dough to change their physical characteristics and improve their ‘machinability.’

“These include surface-active agents (surfactants) to help doughs go through machinery without sticking or tearing, other chemicals to soften the final bread texture or strengthen the dough by modifying the gluten, and a host of emulsifiers just to improve the mixing characteristics or increase shelf life.

“All of these additives have one thing in common: no, or very limited, nutritional value. At least one of them, potassium bromate, has been banned worldwide as a potential carcinogen.”6

There are many other ingredients in bread (or in the things used to make bread) that we as consumers don’t always see on the food’s labels. But here is an example of what is on the label in a loaf of bread we found in our local store:

“Bleached Flour (… Wheat Flour, Malted Barley Flour, Flour, Niacin, Iron, Potassium Bromate, Thiamine, Riboflavin, Folic Acid), Water, Base (Salt, Vegetable Oil, Shortening (Partially Hydrogenated Soybean, Cottonseed And/Or Canola Oil), Dextrose, Sugar, Soy Flour, Cornstarch, Dough Conditioners (Vegetable Mono And Diglycerides, Ascorbic Acid, L-Cysteine, Fungal Amylase), Yeast, Calcium Propionate.”

In addition, another common additive to bread is high-fructose corn syrup. Some brown bread is colored with caramel coloring and while it may contain some whole grain flour, most of it will be refined white flour. 

This kind of bread is high on the glycemic index and gives the consumer a “sugar rush” and more bread cravings. However, it leaves those of us who eat it, starving for nutrition that our ancestors enjoyed every day.

The motivation to remove germ and bran is to extend the shelf life of flour. This makes it white, but producers want it more white, so it’s bleached with either benzoyl peroxide or chlorine gas.”7

The list of additives and behind the scenes processes makes me wonder if commercial bread is even food any more. It seems like a bad chemistry experiment to feed unknowing hordes junk.

Prebiotics and Probiotics

Probiotics contain the good bacteria in our gut and prebiotics are the indigestible fiber that feeds the good bacteria living there. Sourdough’s prebiotics are thought to make that type of bread easier to digest than other kinds of bread. They slow digestion which allows greater absorption of minerals and vitamins from the grain. 

The probiotics in sourdough don’t survive the heat from baking. But during fermentation, the good lactic acid bacteria produced do survive and provide antioxidant benefits, safeguarding your body against illness.

The long fermentation process also breaks down the phytic acid present in wheat, making the nutrients more bioavailable, something that commercially yeasted, refined-flour bread does not do. Michelle from our team explained that in the fermentation of sourdough phytic acid gives up “its death grip” on vitamins and minerals “and lets you actually absorb the available nutrition.  

“That’s where the prebiotics come in. Prebiotics, to quote Dolly Levi, are ‘like manure—pardon the expression.’ It fertilizes the good bacteria in your gut, provides nutrition to your colon, and leads to a healthy digestive system.

“Basically, prebiotics is a type of fiber that feeds the probiotics in your digestive system, releasing more nutrients into your body. It’s an ideal situation for your health.”*

Ideal enough to boost our immune systems?

Katherine Zeratsky, says that we cannot be sure yet, because “the health benefits of currently available probiotics and prebiotics have not been conclusively proved,”  wrote Zeratsky, who has worked at the Mayo Clinic for the last 20 years. However, she went on to explain that “research is ongoing into the relationship of the gut microflora to disease.”

Clarifying the differences, she explained probiotics “contain live microorganisms intended to maintain or improve the ‘good’ bacteria (normal microflora) in the body. Prebiotics are foods (typically high-fiber foods) that act as food for human microflora. Prebiotics are used with the intention of improving the balance of these microorganisms.”8

One study published in the Journal , found: “The gut microbiota are essential for the development of the immune system… Both microbial diversity and abundance in the gut are important to maintain human health. The microbiota is essential to prevent the attachment, growth, and penetration of pathogenic microorganisms on the gut surface. The intestinal microbiota play an important role in pathogen resistance, both by direct interaction with pathogenic bacteria and by influencing the immune system.”9 

Another study found that the extensive community of bacteria (approximately 100 trillion bacteria10 ) in our gut have co-evolved in our intestines and are essential for many of our physiological processes in our bodies including the “development of the immune system, and nutrient acquisition.”11 The study concluded: “Recent studies are providing new insight into the mechanisms by which the microbiota regulates the colonization and eradication of pathogens. Particularly revealing have been studies that indicate that the ability of [a commensal organism, like bacteria] to restrain pathogen growth is dictated by metabolic pathways that control the competition for limited nutrients in the intestine.”12


In my research, I found that the diversity of each sourdough start makes it nearly impossible to find conclusive evidence these cultures have a uniform and positive affect on the human immune system. However, “together with recent medical and technological advances, sourdough-based biotechnology could contribute to improve the quality of life.“13

For nearly a century, we have persisted in the purchase of bread made from white all-purpose flour. This kind of flour is mostly carbohydrates, with the germ and the bran removed. As these are removed, nearly seventy percent of the nutritional value is lost. This makes eating bread, which had been considered as the mainstay of the western diet, a diet of nutritional starvation.

We can turn this around with whole-grain sourdough bread, which slows digestion through the fiber content. This increases the bioavailability of vitamins and minerals, giving us more time to fully absorb them. And it means our systems can be more fully fortified with whole wheat sourdough bread as we face the need for better resistance. Click here to order yours.

In the comment section below tell us about the foods you use to maintain good health. 

Author: Darryl Alder, retired Scouter and outdoorsman, who spent too many hours over a campfire using a dutch oven, and loves sharing recipes for the kitchen and the campfire. You can read many of his recipes here.


1-2 Linsay Patterson, “Sourdough Hands: How Bakers And Bread Are A Microbial Match,” NPR FOOD FOR THOUGHT, 12 NOV 2018
, “Lactobacillus GG: A Potent Immune Regulator Effective in Many Disorders,” Clinical Education Reviews., 07 OCT 2009
4 Maurice E. Shils MD ScDMoshe Shike MD, et al., “Modern Nutrition in Health and DiseaseAug 18, 2005, pp. 1140 & 670
Liljeberg HG1Lönner CHBjörck IM, “Sourdough fermentation or addition of organic acids or corresponding salts to bread improves nutritional properties of starch in healthy humans,”  1995 Jun;125(6):1503-11.
6 Ed Wood,  Classic Sourdoughs, Revised,  Potter/Ten Speed/Harmony/Rodale, Kindle Edition.

Bleached vs. Unbleached Flour, Cooks Country
Katherine Zeratsky, R.D., L.D., What are probiotics and prebiotics?, Healthy Lifestyle, Consumer health, Mayo Clinic
9-10 Angélica T. VieiraMauro M. Teixeira, and Flaviano S. Martins, “The Role of Probiotics and Prebiotics in Inducing Gut Immunity,” US National Library of Medicine
National Institutes of HealthDec 12, 2013
Nobuhiko KamadaGrace Y. ChenNaohiro Inohara, and Gabriel Núñez, “Control of Pathogens and Pathobionts by the Gut Microbiota,” Nature Immunology, Jul; 14, 2013

13 Luana Nionelli,  Carlo G. Rizzello, “Sourdough-Based Biotechnologies for the Production of Gluten-Free Foods,” . 2016 Sep; 5(3): 65.

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