Kristina Campbell, MSc
Practised for millennia, fermentation was originally a way to preserve food. New flavours and textures kept people coming back for more. This article takes a look inside the fermentation crock and discovers the unique health benefits of fermented foods.
Shredded cabbage, water, salt. That’s it. You throw them together in a glass jar and let them settle a while. Peering closely into the jar, you might see tiny bubbles beginning to form along the sides. And if you had a microscope, you might even see the friendly bacteria latching onto the plant material. If you studied the jar for long enough, you’d see that waves of different bacteria proliferate in the jar over time, releasing byproducts that changed the acidity and enzymes inside. And you’d end up with a mixture of your shredded cabbage with lactic acid, some acetic and propionic acid, a mixture of gases (mainly carbon dioxide), trace amount of alcohol, and aromatic esters. In other words, a fantastic batch of fermented sauerkraut.
What is fermentation?
Fermentation is the process by which carbohydrates, like those in plant material or dairy products, are converted to acids, gases, and/or alcohol. In the case of sauerkraut, the micro-organisms responsible for kicking off the process are lactic acid bacteria (LAB)—a diverse group of bacterial species (mainly Lactobacillus, Leuconostoc, and Pediococcus) found naturally on the surface of plants, which produce lactic acid as their main metabolic end product.
Yogurt and some other fermented foods on store shelves are produced in highly controlled environments, so scientists know exactly which strains of bacteria they proffer. But in home fermentation, friendly microbes from the vegetables, the air, and the hands of the maker all combine to produce a microbially different batch every time. Although most fermented foods contain strains of bacteria that are potentially beneficial, these live cultures do not fit the accepted definition of a probiotic, since they are a random, unnamed mix.
Fermentation is considered very safe, since LAB naturally produce substances (including hydrogen peroxide and bacteriocins) that inhibit the growth of food-spoiling bacteria. If you try fermenting at home, however, it’s prudent to familiarize yourself with how to discriminate benign kahm yeast (a harmless fermentation byproduct) from potentially harmful mold.
Preserving food deliciously
Fermented food consumption has been documented for millennia. In the beginning, fermentation was a way to preserve. Human groups throughout history then discovered that certain ways of storing food came with an added bonus: it changed their flavour and texture. Only later with advances in microbiology did we come to understand how the bacteria were doing their work in favourite fermented foods such as yogurt, kimchi, and kefir.
Fermented foods and health
Since the mix of bacteria in each batch is individual and complex, fermented foods are a difficult subject of controlled laboratory study. What scientists know for sure, however, is that the live cultures in fermented foods are key to their health benefits.
Certain bacterial strains, which are present to a greater or lesser extent in a serving of fermented food, have distinct health benefits when tested in isolation. In healthy adults, these bacteria can help prevent acute upper respiratory tract infections, as well as urinary tract infections and allergies, and they can lower cardiovascular disease risk.
Yet a fermented food is more than just the sum of its micro-organisms. Some evidence suggests the food matrix may help boost the beneficial health effects. One mouse study, for example, showed a strain of beneficial bacteria protected against colitis when delivered in fermented milk, but not when delivered on its own.
As well, when it comes to fermented vegetables, the fibre they contain could act as a prebiotic and magnify the effects of the good bacteria, helping them proliferate and produce health-boosting short-chain fatty acids.
Some traditional fermented foods have been studied for their unique effects on the body. Kefir, for example, was the subject of a recent review that presented evidence for its promotion of antimicrobial activity, its contribution to wound healing, and its modulation of the immune system. Studies have also linked fermented food consumption to mental well-being, with outcomes including lower social anxiety and decreased reactions to negative stimuli, although more comprehensive studies are needed to verify these effects in humans.
The finest fermented foods
True fermented foods are not shelf-stable, so if you’re buying them from the store, look for them in the refrigerator section. Live cultures should be listed on the label, and the food should have an expiration date clearly marked.
On the other hand, with a little resourcefulness and a few supplies, you can make delicious ferments at home. Look online for resources on DIY fermenting, or pick up a book such as Joel MacCharles and Dana Harrison’s Batch (Appetite by Random House, 2016; see here for recipes from Batch).
Fermented foods have a long history of use, and they offer so many benefits—for both your health and your taste buds. And if you make them yourself, you’re preserving not just a food but also a moment in time: a microbial snapshot. So what are you waiting for? Dig into that delicious kraut.
Different types of fermented foods
Although fermented foods such as sauerkraut and yogurt can be found widely on store shelves, there are a staggering number of fermented foods from traditions around the world. Here are just a few examples.
Food used |
Fermented product |
Origin |
| Vegetables | ||
| taro | poi (sticky mash) | Hawaii |
| maize | chicha (beverage) | South America |
| Fruits | ||
| papaya | atchara (relish) | Philippines |
| pineapple peel | tepache (beverage) | Mexico |
| Dairy products | ||
| milk | amasi (yogurtlike product) | Southern Africa |
| Meat and fish | ||
| raw fish | funazushi (fermented sushi) | Japan |
| ground pork | nam (sour-tasting sausage) | Thailand |
Cultures that don’t stick around
The process of fermentation dramatically transforms many different foods. No one enthuses over grape juice or milk the way they do over wine or cheese, and it’s because fermentation can permanently change the flavour of food in unique and desirable ways.
In some cases (as in transforming cocoa beans into chocolate), live bacteria are eliminated by the time the food is eaten, while in other cases (as in yogurt and kombucha), the bacteria are alive at the time of consumption. The term “fermented foods” generally refers to those that contain live micro-organisms upon ingestion.
When it comes to making fermented supplements, bacteria can degrade substances like oxalate, phytate, and tannins, making some of the nutrients more available. These supplements do not contain live micro-organisms when you take them. Supplements in this category include fermented cod liver oil, fermented vegan proteins, and fermented mushrooms.
Kristina Campbell, MSc
Kristina Campbell, MSc, author of The Well-Fed Microbiome Cookbook (Rockridge Press), is a science writer specializing in bacteria and the gut microbiome. She lives in Victoria, BC.
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