A little bit of rot is hot to trot these days. That is, food that has been intentionally fermented. And here's why: the process of fermentation sees microorganisms break down the starches and sugars and essentially pre-prepare the food for your digestive system.

All sorts of good bacteria are created along the way, which, when consumed, are believed by believers to boost the health of gut, helping with myriad conditions from IBS to skin disorders and compromised immunity.

Fermented foods are generally made either by introducing a culture inoculate foods, or by simply allowing ingredients to ferment over time in a controlled manner, often with salt added to draw moisture out of the foods and keep mould at bay. Plenty of foods and drinks that we enjoy every day have gone through a fermentation - chocolate, some cheeses, black tea and miso paste among them. But certain fermented foods are considered more powerful than others.

Here are a fantastic five of fermented foods which you can easily introduce to your diet:

Kimchi

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We say 'cheese' to elicit a picture-perfect smile; in Korea, it's "kimchi" that gets those pearly whites showing. This fermented vegetable condiment is Korea's national dish; it has its own museum in Seoul to prove it. The most common type of kimchi is made with cabbage, but turnip, cucumber and spring onions are also used. The vegetables are coated in a pungent mix of garlic, ginger, chilli powder, salt and fish sauce and left to ferment anywhere from a few hours to months. Traditionally, crocks of kimchi were buried in the ground where the temperature remained cool enough to aid a slow fermentation, but today most kimchi is made in purpose-built refrigerators. To Koreans, kimchi is not only a side dish that is eaten with every meal, it's a potent health food - said to cleanse the blood, prevent colds and flus and aid longevity. Kimchi is easy, if not a little whiffy, to make at home, but you can also find it in any Asian grocer. If you're not so keen on the heat factor, try kimchi's pale Euro cousin, sauerkraut.

Kombucha

With a history that stretches back at least 2000 years in China, where it was known as "the tea of immortality", kombucha was a big feature of the popular macrobiotic diets of the 1970s, and is currently enjoying a bit of a comeback. An alien-looking symbiotic colony of bacteria and yeast (SCOBY - but more often called the "mother" or "mushroom") is used to ferment a mix of tea leaves, sugar and water, creating a lightly effervescent drink that some swear is an elixir, and others think tastes like a drinking tap plumbed into the bottom of a compost pile. The SCOBY feeds on the sugar, which gives rise to a host of acids incuding glucuronic, lactic, oxalic that are what give the drink its purported effectiveness. Fans say it boosts energy, detoxifies the body and fights disease.

Kefir

Take yoghurt and multiply its probiotic properties by a few hundred and you have kefir. Originating in the Caucasus Mountains, kefir is made using cow, goat or sheep milk cultured with lumpy grains. The grains themselves are a bit of a mystery; scientists don't know how exactly they came about or how to grow them from scratch so it's just as well there's thriving culture of exchanging grains among friends. Depending how long you let it ferment, kefir can be anything from a slightly tangy, yoghurt-like drink or a fizzing, sour, and ever so slightly alcoholic cocktail of pre and pro-biotics. Some people who can't tolerate the lactose in dairy products are able to enjoy kefir as the end product contains very little lactose - the culture has broken down the enzymes in the milk resulting in a food more suited to our body's digestive system. As well as au naturel, kefir can be enjoyed in smoothies, used to make a sourdough starter or in baking where it acts like buttermilk.

Sourdough

Most commercial bread uses raising agents, like baker's yeast, to turn what would be a flour and water brick into a springy loaf. But before we humans knew how to cultivate yeast, let alone chemicals and additives and preservatives that go in to today's packaged bread, we learned that nature, combined with a bit of care by us, could turn flour and water into a dough that would rise, as if by magic, when cooked. Sourdough bread is made using a starter culture, sometimes called a biga or levain, which is kept alive, nurtured, by continuously feeding it with flour and water. It's a bit carnivorous, really. Like other lacto-fermented foods, a sourdough bread has a slight tang from the lactic acid that is created in the fermentation process. And artisan bakers often attest to the idea that sourdough can be tolerated by those who generally don't tolerate wheat products well; again, that's down to the fermentation basically pre-digesting your food you.

Natto

If you consider yourself a bit of a no-fear eater, here's one to taunt your friends with. It smells like socks, like dirrrrrty socks, and is gooey, stringy texture doesn't help either. Yet in its native Japan, these whole, fermented soybeans are an everyday food, especially popular at breakfast, enjoyed simply with steamed rice and a bit of seaweed paper. And before you snub it, think about what makes a nice ripe Brie - that smell, that ooze - yep, pretty much natto in a nutshell. And like a good stinky cheese, natto smells much more pungent than it tastes.