Fermented Foods for Better Gut Health?

And the role of fibre in your diet

A recent study by researchers at the Stanford School of Medicine investigated two different dietary interventions and their influence on the gut microbiota and immune system in healthy adults.

The dietary approaches were:

  1. A diet high in plant-based fibre
  2. A diet high in fermented foods


What did the study find?

It was a very small study (only 36 participants) but the results are encouraging. The study found that including six portions of fermented foods per day in the diet for a 10-week period resulted in increased diversity of the Gut Microbiota (GM).  We’ve spoken about this before and increased diversity is good for our gut and overall health.

The study also found that including six portions of fermented foods per day in the diet for a 10-week period also reduced markers of inflammation – another very encouraging result. Inflammation is known to be involved in the aging process (now known as inflamm-aging) and it also increases the risk of cancer. So in general, reducing markers or signs of inflammation in the body is seen to be a good thing.

Graphic abstract - Gut-microbiota-targeted diets modulate human immune status
Graphic abstract - Gut-microbiota-targeted diets modulate human immune status

Fibre and Gut Bacteria Diversity

The study also looked at the effect of increasing fibre intake in the diet. They recommended that people eat up to 45g of fibre per day. This is a high amount of fibre and may cause bloating and increased bowel frequency if you have IBS.

This part of the study threw up some interesting results: 

  • The high fibre diet did not increase GM diversity in everyone.
  • The researchers speculate that if you go from a very low baseline fibre intake, then you may actually be missing the necessary GM to ferment and digest the fibre and that it might take longer for a high fibre intake to increase GM diversity. There may be a personalised response depending on your baseline level of GM diversity
  • However, the high fibre diet also reduced inflammation in some people, again this is a good thing

Start Low and Go Slow

These findings would suggest that it’s still beneficial for your gut bacteria to eat a diet that is rich in fibre but that it might take a little longer for some people to see the benefits. 

Fibre plays an important role in reducing the risk of conditions such as diabetes, obesity, heart disease and bowel cancer, so it’s not just our gut bacteria that we need to think about. 

The guidelines vary worldwide but aiming to eat 20-35g of fibre each day is a good place to start. If you wish to increase your fibre intake, do this slowly e.g. by 5g per week and ensure you’re drinking plenty of water. Why? If you increase the amount of fibre you’re eating too quickly, you may experience some unpleasant digestive effects. Nobody wants to experience a fibre traffic jam.

You can learn what a low, very high and recommended fibre diet looks like here.

Fermented Foods – What Should You Do?

If you don’t have a gut condition then the signs are that it may be beneficial and enjoyable to include more fermented foods in your diet. That means including more of the following foods that were used in the study in to your diet:

  • Yogurt
  • Kefir 
  • Buttermilk 
  • fermented cottage cheese
  • Kimchi and other fermented vegetables 
  • Kombucha tea 

If you have IBS or FD you should start with small amounts, particularly with foods like kimchi and see if you can tolerate them. If you can tolerate small amounts e.g. one tablespoon then you could continue to slowly increase your intake. 

Fermented foods can be tricky for people with IBS or FD, as while very healthy, they can cause something of a feeding frenzy for our gut bacteria. Therefore, they may cause uncomfortable gut symptoms such as bloating and wind. 

So, as with fibre, start low and go slow.

 ©The Gut Experts 2021

You can read the study in Cell here.
Featured image courtesy of Brooke Lark.


Share on email
Share on facebook
Share on twitter

Related Articles

Sign up for our newsletter

to get the latest gut health insights,

our top tips, recipes and more.