What Is Prebiotics

Updated on :

Prebiotics and probiotics have gained a lot of attention in recent years, especially when it comes to digestive health.

In this article, we will dive deep into what is prebiotics, what are the benefits, and what the medical research says about them.

Scientific definition

A substrate that is selectively utilized by host microorganisms conferring a health benefit.

Basically, prebiotics is food for probiotics. Probiotics are microorganisms that live mainly in our gut and have many health benefits.

Prebiotics are nondigestible fiber compounds found in food. Prebiotics help enhance the population of probiotics in our gut.

Types of Prebiotics

Fructans ( Insulin type Fructans and Fructo Oligosaccharides FOS )

They are mainly found in foods like garlic, onions, asparagus, and artichokes. Apart from stimulating the growth of probiotics, fructans are known to have immunomodulatory properties which can reduce inflammation of the gut.

Galactooligosaccharides ( GOS )

GOS is mainly found in beans, dairy products, and root vegetables. These also help the growth of Bifidobacteria and Lactobacilli and are thought to reduce allergies such as eczema, and weight loss effects and most recent findings have anti-anxiety properties.

Starch and Glucose Derived Oligosaccharides 

These are like dietary fiber and mainly have benefits for obesity and metabolic diseases such as diabetes and cardiovascular health.

Benefits of Prebiotics

Gastrointestinal disorders

Irritable Bowel Syndrome and Crohn’s Disease 

Prebiotics has immunomodulatory properties ( regulate the immune system) thus reducing inflammation. Two recent randomized, double-blind trials have shown that taking Fructans ( Fructo Oligosaccharides FOS ) for 5g/ day reduces the symptoms of IBS.

Similar studies for Crohn’s disease carried out with a higher doses of 15 g/day showed an increased Bifidobacteria population and improved Crohn’s disease.

Colorectal Cancer

Prebiotics-induced fermentation release of butyrate reduces the risk of colon cancer by reducing the rate of proliferation in colon cells.

Immune system

 Prebiotics helps boost the immune system by increasing the number of protective microorganisms. Human and animal studies have shown that prebiotics decreases the population of harmful bacteria by promoting the growth of Lactobacilli and bifidobacteria.


Prebiotics improves cardiovascular health by regulating the lipid profile ( ie fat level in the blood vessel), reducing body weight thus producing an overall protective effect.

Nervous system

Memory, concentration, and learning

Numerous studies have been conducted on different types of prebiotics and memory improvement. In middle age adults, it has shown general improvement in cognition but more concise studies are yet to be done. The recent conclusion is that prebiotics helps with preserving recall and learning rather than the development process of the brain which means no effect on preventing dementia or age-related memory decline but might have a good effect on recalling existing memory.


Scientists measure the level of stress hormones following exposure to controlled stress and then gave Bifidobacterium infantis, then they found stress hormone levels were reduced.

Skin and Bone

Including prebiotics in the diet has been shown to reduce the risks of allergic skin diseases such as atopic dermatitis, and eczema.

Prebiotics enhances the absorption of calcium from the gut but whether it reduces the risk of fractures or osteoporosis is still uncertain.

Prebiotics-rich food


  • Mushrooms
  • Garlic
  • Leek
  • Asparagus
  • Green peas
  • Cabbage
  • Eggplant
  • Onions


  • Chickpeas
  • Baked beans


  • Watermelon
  • Grapefruit

Whole grain

  • Oat
  • Rye
  • Wheat
  • Cocoa

Should I take prebiotics supplements?

General advice is that it is always best to optimize diet. However, the food we eat every day is more and more processed. It has become more and more difficult to obtain natural, lean food.

Although there are lots of research evidence for prebiotics, strong evidence for supplementing prebiotics is still lacking.

Side effects of prebiotics

Prebiotics are not known to cause any serious side effects. Since they are indigestible fiber the main side effects are bloating, diarrhea, cramping, and flatulence.

Who should not take prebiotics?

For people who have a severe systemic illness, active inflammation in the gut, immune suppressed individuals due to a disease, or taking tablets that lower the immune system.

It is always best to consult with a doctor before taking anything even supplements.

Photo of author
Dr Tun Min is s GP working in NHS UK and writing articles about supplements and vitamins based on personal clinical experience and clinical research.

Leave a Comment