SIBO Part #3 – Diet & Fermentable Carbohydrates

Anyone dealing with a SIBO diagnosis will know treating SIBO isn’t straightforward.  It can be a long and drawn-out process, with many people experiencing relapse or struggling to eradicate the bacteria in the first place.

After being diagnosed with SIBO, I was relieved to find a specialist in the area, Dr. Natalie Cruttenden, who put me on a protocol to eliminate my SIBO.  For the last 6 weeks I’ve been following a very low carbohydrate diet while taking herbal antimicrobials in the hope of conquering my digestive woes once and for all.

Success!  Well partly.  Last week I retook the lactulose breath test which measures the methane and hydrogen being produced in the stomach, and is the best indicator for measuring SIBO.  You can read more about breath testing here and here.  Previously my methane levels were very high with hydrogen only slightly elevated.  After the 6 weeks, the good news is that the methane has reduced by half!  Happy dance.  When reducing methane a risk is that hydrogen can then increase; luckily this hasn’t happened with me, and my hydrogen levels are now in the single digits.  The bad news is that I do need to complete another 6 week protocol to (hopefully) clear my SIBO.

So in light of committing to the SIBO Diet for another 6 weeks, I thought it timely to delve deeper into the ‘whys’ of reducing fermentable carbohydrates in the diet.

What are Fermentable Carbohydrates?


There are a few types of fermentable carbohydrates (also know as saccharides), that are found in many common foods,  including:

  • Starch – grains, beans potatoes;
  • Resistant Starch – whole grains, seeds, legumes;
  • Soluble Fibre – grains, nuts, fruit & veg;
  • Sugar – sweeteners, fruit, milk products (lactose);
  • Prebiotics  – vegetables, supplements.

In people with SIBO, these carbs feed the bacteria in the small intestine and are the source of much digestive upset.  By reducing the amount of fermentable carbohydrates in the diet, the bacteria aren’t able to thrive, and when diet is used alongside medication, this is thought to be the best way to eliminate SIBO.

But aren’t vegetables good for us?


Yes!  We need to eat a wide array of vegetables to get appropriate amounts of essential vitamins and minerals in the diet.  The key here, is that we are reducing not eliminating the fermentable carbohydrates.  So whilst high carbohydrate veg like potato, sweet potato, garlic and onion are off the menu, you can eat unlimited amounts of other vegetables like leafy greens, tomatoes, eggplant, and capsicum.  Other veggies need to be moderated due to their fermentable load, these include beetroot, pumpkin, brussel spouts, cauliflower and broccoli.  While half a cup of these vegetables is usually tolerated, a larger serve can cause a SIBO flare, which will slow the progress of your healing journey.

The main offenders:


While vegetable need to monitored, and some eliminated for the period, the main offenders with the highest fermentable load are grains, sugars and dairy.  These foods tend to have high levels of fermentable carbohydrates, and should be avoided as much as possible whilst you are dealing with SIBO.

So what can you eat?

I won’t lie – eating out is hard!  No onion, garlic, grains, legumes or dairy does prove challenging for many places.  A simple protein dish + salad or veg is the way to go.  Just don’t expect it to be the most delicious meal you’ve ever had.

Cooking at home has taken some adjustment, but after 6 weeks has become second nature, and I still manage to get plenty of flavour in my meals using various herbs and spices.  On the menu is:

  • animal proteins – eggs, fish, chicken, lamb, beef
  • healthy fats – nuts/seeds, olive oil, coconut oil, ghee, avocado, coconut milk
  • low-fermentable vegetables 
  • low-sugar fruit – berries & citrus
  • lactose-free dairy – butter & aged cheese
  • treats – small amounts of 90% dark chocolate and occasional red wine

Fingers crossed I’m SIBO-free in another 6 weeks!



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