How does food affect the gut microbiome

14th October 2022

You are what you eat, particularly when it comes to your gut microbes.

The food we eat affects the health of our gut microbial community. A rich, varied diet can help our microbes thrive while a restricted diet can impede our gut microbiome’s health and impact the growth of certain beneficial bacteria.

We explore how some foods affect the gut microbiome.


Fibre is important for gut health. Dietary fibre is found in plant-based foods, including vegetables, cereals grains and pulses, where the plant cell wall is the main source of dietary fibre.

Humans do not have enzymes that digest dietary fibre. Instead, dietary fibre passes through the digestive system to the gut microbiota, where microbes can digest it for us.

It is recommended we eat 30g of fibre a day. Despite this, adults in the UK only eat about two-thirds of the recommended daily intake. Soluble fibre has prebiotic properties, and eating the recommend 30g of fibre a day can help your gut microbiome produce more essential short-chain fatty acids.

At the Quadram Institute we’re looking at ways to increase the quality of fibre in diets to help promote a healthy gut microbiome.


Foods can come with their own microbes that are beneficial to us. These are called probiotic foods, as they aim to deliver live microbes into the microbiome.

Dairy products like yoghurt, kefir and cheese; and preserved vegetables like olives, sauerkraut and pickle, are made with bacteria via lactic acid fermentation.

Friendly moulds can be found in dairy products, such as blue cheese.

It’s important to note that not all foods containing live cultures meet the definition of a probiotic.


Carrots contain high amounts of compounds called carotenoids, which have been shown to alter gut microbiome composition and regulate gut immune function.

Other fruit and vegetables that are red, yellow and orange contain carotenoids such as apricots, melons, carrots, mangoes, and sweet potatoes.

Research at the Quadram Institute is investigating the effects of such carotenoids and other plant bioactive compounds.


Brassicas are a group of vegetables that includes broccoli, cabbage, cauliflower, kale and brussel sprouts.

Researchers at the Quadram Institute have found that increased consumption of brassica vegetables is linked to a reduced amount of sulfur-reducing bacteria in the gut microbiome which may potentially be beneficial to gastrointestinal health.


Cereals and nuts contain phytic acid, which is thought to have benefits for our health. Phytic acid could help achieve a better microbial balance.

Phytic acid in the intestine can bind to iron. Iron is an important nutrient for our health and is absorbed in the small intestine. Unabsorbed iron passes through to the large intestine, where the majority of our gut microbes live.

A type of potentially harmful bacteria that can colonise the large intestine relies on this iron. A research team at the Quadram Institute previously carried out a study to investigate whether delivering a form of phytic acid to the large intestine binds excess iron to decrease the proportion of ‘bad’ bacteria in the microbiome.


A wrinkled ‘super pea’ has been shown to benefit the gut microbiota thorough delivering resistant starch to gut microbes.

Resistant starch escapes digestion and reaches the large intestine where it gives energy to the complex bacterial community that live there.

Leftover food

Leftover carbohydrates such as cooked pasta and potatoes also contain resistant starch which can help look after friendly gut microbes.

Research at Quadram is exploring what happens in potatoes left in the fridge for a day or two and how this benefits the gut microbiome.

Related Targets

Targeting Future Foods

Future Foods

Related Research Areas