Leeks are one of the few foods that contain prebiotics (others include garlic, onions, artichokes and asparagus). Most people have heard of probiotics, the friendly bacteria that help keep our intestines healthy, but it is believed that we need prebiotics to help feed our probiotic bacteria.

Prebiotics - which include inulin and fructo-oligosaccharides - are mainly carbohydrates that cannot be broken down by our body's own enzymes, so they pass through our digestive system and into the colon in the same state that we ingested them. Once in the colon, they act as a food for the probiotic bacteria and as a result help to increase the friendly bacteria.

Nutritionists believe that we need to eat approximately 7g of prebiotics a day to have a positive impact on our gut bacteria. A bowl of leek and artichoke soup can contain around 6g of inulin and if we also eat a couple of bananas we will have possibly exceeded our target. The fresher the produce, the higher its prebiotic content; as always, fresh is best.

British leeks are available year-round except in June. The season peaks in September and November and again in the spring, coinciding with St David's Day (the leek is feted as the national symbol of Wales).

Allium porrum is the type of leek cultivated in the UK; it thrives in cool climates and is tolerant of frost. It is a member of the onion family and has many of the same health benefits as onions, such as helping to maintain a healthy heart and circulation, protecting against cancer and generally boosting the immune system.

Leeks can be cooked slowly in stews or soups, or pre-cooked and added to tarts and quiches. They are equally delicious tossed quickly in hot oil and butter and served alongside meat or fish. I also love steamed leeks wrapped in ham, covered in cheese sauce and lightly grilled until golden - a meal particularly popular with small children.