Fermented vs. Probiotic Foods – What’s the difference?
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Gut health and the use of fermented and probiotic foods are a hot topic these days. There’s no doubt that you’ve heard mention of the ‘gut microbiome’ and have some idea that gut health is important. A quick internet search will result in a plethora of entries about how to improve your gut health by modifying your diet, particularly with the inclusion of fermented or probiotic foods as a means to do so. The idea is that if we can alter our diet and, in turn, change the gut microbiota we can potentially improve our gut health…and maybe, just maybe, our overall health, too.
So, what’s the deal with fermented and probiotic foods? What are they and are they worth including in your diet? Let’s find out.
A (very) brief summary of the microbiome…
While knowledge and understanding of the true complexity of the human microbiome is still in its infancy, there are some things that we do know about it, including:
Humans have trillions of microbes living on and in them symbiotically, including on the skin, in the nasal/oral cavities, on the genitals, in the respiratory tract, and in the digestive tract. Each of these areas are composed of different types and amounts of microbes.
These microbes include bacteria, viruses, protozoa, and fungi.
This ecosystem, or microbiome, is very important for our health.
The collection of microorganisms that dwell in our gut is often referred to as the gut microbiota.
In the digestive tract, some of the known mechanisms by which these microbes elicit health effects include producing short chain fatty acids (SCFA) which feed the cells of the gut, regulating the immune system, protecting against pathogens and synthesizing vitamins (just to name a few actions).
Microbiome diversity (that is the amount of different microbes present in the gut) is associated with better health outcomes. Low diversity is associate with disease states (but we do not know if low diversity causes disease states).
The gut microbiota is influenced by diet, geography, stress, medications, and disease states.
No one person’s microbiome is identical.
Some microbes are more beneficial than other. There are so-called “bad” microbes living in our gut but it is not the presence of them which is a problem (we all have them). The problem often is more related to the amount or ratio of bad to good microbes.
Image from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4838018/
Essentially, we know that the gut is inhabited by a tonne of microbes and these microbes, in some way, convey some sort of effect on our health. As such, there’s lots of interest in how we can modulate the state of our gut microbiota.
Fermented vs. Probiotic foods – What’s the difference?
Eating patters have, rightfully so, gained a lot of attention as a means to improve the gut microbiome, particularly through the use of probiotic and fermented foods.
Fermented and probiotic foods are often used interchangeably but they are not the same. There are some fermented food that are probiotics and some that are not. And some probiotic foods have been fermented while some have not been. Sounds a bit confusing, doesn’t it? Let’s take a closer look at these probiotic and fermented foods to help sort out the differences.
The use of bacteria and yeasts in the process of fermentation goes back thousands of years as a form of food preservation. Foods like beer, wine, cheese, miso, sauerkraut, and yogurt all use microbes to transform (or ferment) food substrates, like sugars, into other substrates which produce their distinct final product. Taste profile, acidity, carbonation and even altered nutrition can be the result of this fermentation process.
All fermented foods, at one point in time, use live microbes in their production, however, not all fermented foods contain live microbial cultures. Some processes used in food production remove or kill the live microbial cultures. Sourdough bread is a good example of this – fermentation by yeast is responsible for the production of sourdough bread but the baking process kills the yeast, so that the final product does not contain live microbial cultures. Another example is a shelf stable sauerkraut (found in the unrefrigerated aisles in the grocery store) – the cabbage in this type of sauerkraut was fermented but to increase its shelf life in the grocery store, it has been pasteurized which has effectively kills the microbes which fermented the product.
Probiotics are defined by the Food and Agriculture Organization (FAO) and World Health Organization (WHO) as "live microorganisms which when administered in adequate amounts confer a health benefit on the host". Accordingly, for food (and supplements) to officially qualify as a probiotic they must meet the following criteria:
Properly labelled. This means for any food or supplement to be considered a probiotic, they must be labelled with the specific microorganism type – that is with the genus, species, and strain. For example: Bifidobacterium (genus) longum (species) 35624 (strain)
Proven health benefits. There must at least one positive, human, clinical trial that shows the microorganism in question has beneficial effects. This is why proper identification is important as different microorganisms have different proven health effects.
Adequate dose. The dose must be indicated in CFUs (colony forming units). This dose must be at minimum the dose of live microorganisms found in clinical studies to show health benefits and remain at this level until the indicated expiry date the product or food.
Safe for use. This is sort of self explanatory, right?
In short, food manufacturers can use the official ‘probiotic’ claim on their food labels if they meet the above criteria. You may find a certain yogurt that can sport the word probiotic, due to its live bacterial culture present being in an amount that has been shown, in human studies, to confer beneficial health effects. Or you may find some probiotic functional foods (these are defined as foods with health-promoting additives) sitting on your grocery or health food store shelves. Some of these functional foods could have been fermented or have had probiotics added to them.
Turning our attention back to the broader category of fermented foods, we can see that fermented foods could officially be considered probiotic foods, if they meet all the criteria listed above. However, to meet said criteria, there would have to be some testing to identify the strain and quantity of microbes present. The reality is that for many food manufacturers (and for those fermenting food at home, of course), it is unlikely that these criteria will be met.
Are Fermented Foods Good for You?
If some fermented foods aren’t considered probiotics, does that mean that they aren’t as healthful as we thought? Should we only look for those foods labelled probiotic? Certainly not!
While some fermented foods contain live microbial cultures that are themselves what causes beneficial health effects, the process of fermentation also modifies food components into bioactive compounds and these compounds (not necessarily the microbes themselves) can be beneficial.
Let’s take a closer look at what some studies have found about fermented food and health. Of course, this is not an exhaustive list of the studies out there (or else we’d be here for a long time), it’s merely a sample of studies that show the potential benefits of including fermented foods in our diet.
Fermentation of milk increases its antioxidant content, for example, in yogurt or kefir. One specific antioxidant produced during fermentation of milk is Conjugated Linoleic Acid (CLA). Antioxidants, such as CLA, are used by the body to neutralize cell-damaging free radicals molecules.
Another interesting action of fermentation in dairy products (depending on the bacterial starter used) is the formation of folate, or vitamin B9. Folate is needed for the synthesis of genetic material (DNA and RNA), protein metabolism, the formation of healthy red blood cells and for fetal development. Along with folate, B12 is also increased in some fermented dairy products, as much as a 10 times increase in some cases. In addition, certain lactic acid bacteria can cause an increase in vitamin K content of fermented dairy, which is beneficial to bone and heart health.
Some fermented dairy products have also been found to contain more anti-hypertensive peptides than their non-fermented counterparts. A meta-analysis of 14 randomized placebo-controlled trials, found that fermented milk produced a reduction of both systolic and diastolic blood pressure in pre-hypertensive and hypertensive subjects. Note: If you have high blood pressure, you probably don’t want to ditch your medication for yogurt but perhaps used in addition, or incorporated into your diet if you have a strong family history of hypertension as a means of prevention (in addition to other strategies).
The fermentation of wheat flour, in the making of sourdough bread, has been shown to increase the content of resistant starch and decrease the overall glycemic index. This means that eating sourdough bread, when compared to bread made without fermentation (i.e. regular wheat bread), there is a less dramatic effect on your blood sugars after consumption. For those with blood sugar regulation issues this is important.
The fermentation process of making sourdough bread also decreases the FODMAP content (more specifically the fructan content), compared to regular bread. This is an important factor for those with Irritable Bowel Syndrome (IBS), as FODMAPs can trigger symptoms and an elimination and/or decrease of such dietary components can great improve symptom control.
Fermentation can improve iron bioavailablity of some vegetables, including carrots, beets and sweet potatoes. As plant-based sources of iron are not as accessible to us during the digestion process, fermentation may improve our body’s ability to utilize this mineral.
Several studies (albeit small studies) have shown that kimchi, the Korean fermented cabbage dish, may have a positive impact on both blood sugar levels and cholesterol levels.
In a recent (2021) 10-week dietary intervention study, a diet high in fermented foods were found not only to increase the diversity of the microbes present in the gut (which is a very good thing) but also to decrease markers of inflammation.
As you can see, fermentation is not only a way to preserve food or change particular taste characteristics, but also can impact our health positively. While it is a common belief that the benefits of fermented foods are due solely to the presence of live bacteria and only act in the gut. The truth is that these live cultures don’t necessarily need to be present in a fermented food at the time of consumption to elicit positive health effects. Microbial fermentation can alter food components and these health-promoting products of fermentation (called postbiotics), and not necessarily the microbes themselves, can be what we benefit from. Pretty cool, isn’t it?
To recap, there are certainly similarities between probiotic and fermented foods but they aren’t always the same thing. Foods labeled as ‘probiotic ‘ contain live microbial cultures which have been shown, in human studies, to confer health effects. Fermented foods, as their name indicates, use fermentation sometime during their production but don’t necessarily contain live cultures (although a lot still do). Realistically, many fermented foods you encounter in your day to day life are unlikely to meet the official criteria for a probiotic, not necessarily for lack of microbial content but more for logistics of getting tested. This is especially true for small scale fermented food production and for those who make fermented food at home.
Fermented foods, while not always meeting the probiotic criteria, certainly have been shown to be a healthy addition to your diet. Incorporating these foods may directly affect your gut microbiome due to their live microbial content, or provide you with other health effects from the products of fermentation, as some of the studies indicated above. With so many delicious, fermented foods available, adding them to your diet is an great way to add variety to your diet and, possibly, improve your overall health.
