Fermented Foods & Gut Health

Fermented foods are becoming increasingly popular for improving gut health. We often hear about their beneficial effects, but what exactly falls into this food category? What is fermentation? Do all fermented foods contain live bacteria? And why are they so important? 

Let’s take a look at the science behind fermented foods and why not all of them are equal.

What is Fermentation and Why Does it Benefit Our Gut Health?

In simple words, fermentation is a metabolic process that occurs when certain types of microorganisms - mainly bacteria - modify the composition of our food and beverages.

Humans have been fermenting food for ages to increase flavor or to preserve foodstuffs. Today, we know that these live microorganisms are beneficial for gut health, they can produce vitamins, and they also have a potential role in reducing inflammation.

You can learn more about fermentation and its gut health benefits in our podcast episode with professor Dennis Sandris Nielsen from University of Copenhagen

What are the Different Types of Fermentation?

There are two main methods. Foods can be fermented naturally, known as “wild ferments” or “spontaneous ferments”, where the microorganisms are present naturally in the raw food or processing environment. This is the case with sauerkraut, kimchi, and certain fermented soy products. 

Foods can be also fermented via the addition of starter cultures, often referred to as “culture-dependent ferments”, for example, yogurt, cheese, wine, beer kefir, kombucha, and natto.

 What is the Definition of Fermented Food?

According to The International Scientific Association for Probiotics and Prebiotics (ISAPP), an expert panel convened to clarify the inconsistencies around the term ‘fermented’; fermented foods and beverages are “foods made through desired microbial growth and enzymatic conversions of food components”. 

This definition includes food items that are made by fermentation but might not necessarily have the live bacteria, when we consume them. Meaning that although in some part of the processes the bacteria are inactivated or extracted, these products still belong to the category of fermented foods. 

A clear example of this is leavened bread where the baking process eliminates the microorganisms or some beers and wines where the bacteria are removed from the final product.  

Not All Fermented Foods are the Same 

There are probably a myriad of different types of fermented foods consumed worldwide. Although the formal definition of fermented foods is very broad, it is important to take into account some practical aspects to choose those that benefit our intestinal health the most. 

But the question that arises so often is whether all these items are equally beneficial. Is it the same to eat yogurt, kimchi, sauerkraut, or drink kombucha?

How Should I Shop for Fermented Foods? 

Here we present three basic aspects that you should take into account when choosing what to buy: 

1. Does the fermented foods contain living microorganisms?

The most important distinction is whether or not the fermented foods contain live microorganisms at the time of consumption. The key is to read the packaging labels and look for statements like “contains live and active cultures” or some products will also list the microbial strains that they contain. The single claim “foods made by fermentation” does not ensure the presence of living microorganisms.

2. Watch out for added sugar

Unfortunately, many products that we normally perceive as “healthy” are loaded with amounts of added sugar that exceed the recommended limits. This is the case of flavored yogurts or versions of kombucha that we find on supermarket shelves.

Here once again it’s a good idea to get used to reading food labels and checking ingredients, to choose products in their natural format, with lower sugar, or sugar-free.

And don’t be fooled: Sugar can be named in various ways, such as corn sugar, dextrose, fructose, glucose, high-fructose, invert sugar, isoglucose, maltose, molasses, or sucrose to name just a few!

3. Try fermenting at home

Despite the rumors, fermenting isn’t that complicated. It takes a bit of preparation and then the bacteria do all the hard work. 

If you are up for experimenting, you could start with one of the simplest fermented foods to do at home: sauerkraut. Easy to make, requires very little special equipment, and tastes delicious. 

Do you want a look into your personal gut microbiome and what bacteria you have, then you can get insight with a gut microbiome test from Unseen Bio. 

If you want to dive deeper into the gut microbiome, then listen to our podcast "Mikrobiomet" (The Microbiome), where we explore everything science knows about gut health and the microbiome together with a broad range of microbiome experts. 

You can also read more about different food’s impact on the gut microbiome in our other articles. 

By Cecilia Clausen (Clinical Dietitian)