Despite the trends for carb free diets, carbohydrates are a major macronutrient and one of the body’s most readily available sources of energy. Not only are carbs extremely important for a balanced and healthy diet but they also can have a positive effect on our gut health.

Simple Carbs

Carbohydrates are made up of three components, fibre, starch and sugar and come in two forms. Simple carbs (simple sugars) such as lactose & fructose which can come from fruit but also products containing refined sugar & grains such as cakes, white rice & pasta. Often eaten in excess and rightly so, are often thought to be the devil for weight gain and unhealthy diet.

Most simple starches are broken down by enzymes in our small intestine into sugar, which is then absorbed into the blood. As sugar levels rise, the pancreas releases the hormone insulin, which is needed to move sugar from the blood into the cells, where the sugar can be used as energy.

This gives the body a sugar spike and although a short-lived increase in energy, if your output is minimal, this sugar can turn to fat and has been blamed for the increase in obesity & diabetes. These starches can also have a negative effect on your gut bacteria.

Complex Carbs

Complex carbs are packed with more nutrients, are higher in fibre & starch and digest more slowly. Ideally, we want most of the carbohydrates in our diet to be in this form. These contain long chains of glucose that are found in grains, potatoes, beans, starch-based fruit & vegetables, lentils, wholemeal pasta etc. Most of us often think carbs are bread & pasta but many fruit & vegetables contain are our high fibre carbohydrates.

Resistance Starch

Not all starch you eat gets digested in the small intestine. Certain types of carbohydrate (beans, legumes, starchy fruits such as bananas, whole grains, cooked & cooled rice & potatoes) resist digestion in the small intestine and ferments in the large intestine. These ferment fibres act as a prebiotic and feed the good bacteria in the gut.

Because resistant starch is not digested in the small intestine, it doesn’t raise glucose. This means there are no spikes & troughs in energy levels and GUT health is improved from the fermentation of the fibres, creating more good bacteria in the gut.

The bacteria in your intestine outnumber the body’s cells 10 to 1. Most food feeds only 10% of the body’s cells, whilst fermentable fibres and resistant starches feed the other 90%. So, you can imagine how important they are to our bodies, helping to: 

  • stimulate blood flow to the colon
  • increase nutrient circulation
  • inhibit the growth of pathogenic bacteria
  • help us absorb minerals
  • help prevent us from absorbing toxic/carcinogenic compounds

Short Chain Fatty Acids

Eating resistance starch & high fibre food, is linked to an increase in short-chain fatty acids. Your friendly gut bacteria digests carbohydrate fibres and turns it into short-chain fatty acids. One of the most important of these short-chain fatty acids produced being BUTYRATE, which is the preferred fuel for the cells that line your colon. 

Unlike most other cells in our body which use sugar (glucose) as their main energy source, the cells of the lining of our gut (colonocytes) mainly use butyrate. Without butyrate, these cells would not be able to carry out their functions correctly, helping to reduce inflammation and keep gut cells & bacteria happy and healthy. Butyrate also functions as a “HDAC inhibitor”, meaning that it performs anticancer and anti-inflammatory functions by suppressing the activity of specific immune cells. 

Therefore, resistant starch both feeds the friendly bacteria and indirectly feeds the cells in your colon by increasing the amount of butyrate.


In addition to the above, resistances starch/short chain fatty acids are seen to reduce type 2 diabetes, obesity, heart disease and other conditions. It reduces our pH level, which in turn reduces inflammation and have been seen to lower your risk of colorectal cancer and may aid various digestive disorders. This includes inflammatory bowel diseases like ulcerative colitis and Crohn’s disease, constipation, diverticulitis and diarrhoea. It also helps reduce gas (due to the fermentation of fibres), leaves you feeling fuller and lowers cholesterol.

It’s is worth noting that high-protein, high-fat, low-carbohydrate diets have been shown to disrupt butyrate production and therefore means we create less of the above health benefits.

Increasing Resistance Starch into your Diet

As mentioned, resistance starch is naturally present in foods such as bananas, potatoes, grains, legumes, fruits, vegetables and seeds etc.

By cooking and cooling or freezing carbs like pasta, potatoes, rice or bread and reheating (making toast from frozen bread etc) changes the molecular structure of the carbohydrate, increasing the resistant starch. Additionally, for those conscious about weight gain or losing weight, the higher the resistant starches in food content, the lower the calories (as they are not turning into sugar in the small intestine)! 

If you’re currently trying to break a weight loss plateau, have high blood sugar, digestive problems or if you’re simply in the mood to increase your good gut bacteria; then eating more resistant starch could be the way forward. Far too often diets restrict foods which contain carbohydrates & this high resistant starch. Now is the time to ditch the idea that all carbohydrates are the devil, in fact they are essential to a healthier you.

One thought on “How to feed your good gut bacteria with carbs

  1. Claire says:

    Thank you for this – it is most instructive and helpful. I have been on keto and low carbs for about 3 years and have recently stopped eating this way because – approaching my menopause, I found I was increasingly anxious and depressed, plus I started to binge on the less healthy carbs. I do feel tho, that I have become psychologically ‘scared’ of carbs, believing myself to be slightly intolerant of them. This article really helped me to see how wonderful they truly are. Thank you!!!

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