Should I be eating more prebiotics?

What are prebiotics?

A prebiotic is a type of non-digestible fibre that promotes the growth of beneficial organisms in the intestine. As prebiotics aren't digested in the stomach or small intestine, they reach the colon (large intestine) and are fermented by the bacteria in the gut to be used as an energy source. In other words, prebiotics are the food or energy source for the healthy bacteria found in our gut.

In order to be classified as a prebiotic, it must:

• Pass through the gastrointestinal (GI) tract undigested,
• Act as food and stimulate the growth and/or activity of certain 'good bacteria' in the colon,
• Induce effects that are beneficial to the health of the host by making the gut environment healthier.

Sources of prebiotics

Chances are you're already eating some prebiotics in your normal diet. Good sources of prebiotics are listed in Table 1. As a general rule, to get the most out of the prebiotics found in vegetables, they should be eaten raw, for example in salads, smoothies or hummus, or otherwise gently cooked such as by steaming. In addition to being good sources of prebiotics, many of these foods are also excellent sources of dietary fibre which is recommended for a well-balanced diet.

Table 1: Food sources of prebiotics

Vegetables	Chicory root, Jerusalem artichokes, garlic, onions, leeks, asparagus, dandelion greens
Legumes	Chickpeas, lentils, red kidney beans, baked beans, soybeans
Fruit	Unripe bananas
Wholegrains	Barley, rice, quinoa, oats

Health benefits

Prebiotics are a relatively new topic of discussion, and are far less well-known than 'probiotics' – cultures of live microorganisms, often termed 'good bacteria', that confer a health benefit by rebalancing the balance of bacteria in the gut. The evidence backing the health benefits of prebiotics is still limited and requires further investigation, although it is suggested that prebiotic intake may:

• Reduce the prevalence and duration of diarrhoea associated with infections or antibiotics.
• Reduce symptoms associated with inflammatory bowel disease.
• Exert protective effects to prevent colon cancer.
• Reduce episodes of constipation.
• Enhance the uptake of minerals including calcium which may maintain bone density and reduce the risk of developing osteoporosis.
• Lower some risk factors for cardiovascular disease.
• Promote satiety (feeling full after a meal) and weight loss to prevent obesity.

Irritable bowel syndrome

Although the health benefits of prebiotics sound great, they're not for everyone. Patients with irritable bowel syndrome (IBS) for example are advised to follow a low FODMAP diet. FODMAPs are indigestible sugars that act as 'fast food' for gut bacteria. In IBS, FODMAP foods are poorly absorbed in the small intestine and are instead fermented by bacteria in the colon, producing gas and contributing to the symptoms of IBS. Unfortunately many of the foods that are good sources of prebiotics are also high-FODMAP foods and are not advised for IBS sufferers, so if you are considering a noticeable change to your diet it is important to discuss your options with your doctor or dietician.