Probiotic literally means ´for life´ and involves using live, ´friendly´ bacteria to improve digestive and immune health. The science of probiotics is one of the most exciting areas in nutritional medicine.

The wealth of research confirming the benefits of replenishing probiotic bacteria is growing daily and an increasing number of doctors recommend their use - even in hospital. You may not realise it, but there are ten times more bacteria in your intestinal tract than there are human cells in your body. The most important intestinal bacteria are those that produce lactic acid through fermentation of glucose. These are known as probiotic bacteria and include species such as Lactobacillus acidophilus and Bifidobacterium longum. Ideally, at least 70% of the 11 trillion bacteria in your gut should be ´probiotic´ with only 30% consisting of others such as E.coli. In practice, however, the balance is usually the other way round, which is bad news for your intestines and your general health.

Probiotic bacteria help to reduce overgrowth of harmful yeasts and bacteria in your intestines in a number of ways. They produce lactic acid, acetic acid and hydrogen peroxide which lower intestinal pH and discourage reproduction of less acid-tolerant, harmful bacteria. They also secrete natural antibiotics (bacteriocins such as acidophiline and bulgarican) and stimulate production of interferon - a substance which helps to protect against viral infections. Probiotics also compete with harmful bacteria for available nutrients and for attachment sites on intestinal cell walls. If these sites are already occupied by friendly bacteria, potentially harmful microbes cannot gain a foothold in your intestines so easily and are more likely to get flushed out.

As a result of all these beneficial actions, probiotic bacteria have a powerful, protective action against a number of intestinal infections - especially those responsible for travellers´ diarrhoea such as Bacillus cereus, Salmonella typhi, Shigella dysenteriae, Escherichia coli and Staphylococcus aureus. Even if you don´t take probiotics at any other time, you should definitely consider them when travelling abroad. Probiotics can also reduce the well-known intestinal side effects of broad-spectrum antibiotics which, as well as killing harmful bacteria, will also deplete your natural population of healthy, probiotic microbes.

Studies suggest that lack of probiotic bacteria in the colon is common and can result from previous antibiotic treatment, stress, general infections, poor dietary habits, smoking and alcohol consumption. Lack of probiotic bacteria in the intestines creates an unhealthy environment that allows other, potentially harmful organisms - viral, bacterial and fungal - to thrive. This can lead to the development of a number of health problems, including food intolerance, bloating, flatulence, diarrhoea and constipation. It may even increase the chance of developing long-term intestinal problems such as diverticular disease and irritable bowel syndrome.

Research shows that probiotic supplements can significantly improve symptoms associated with irritable bowel syndrome and, although they are beneficial when taken alone, they can also be used in combination with antispasmodic IBS drugs to boost their effectiveness. In Scandinavia, probiotic supplements are now widely used in hospitals to maintain healthy intestines in patients who have undergone abdominal surgery or who have experienced severe trauma; they are also given to infants with intestinal infections, and to those who are failing to thrive as a result of serious illness. Another benefit of probiotics is that they appear to reduce the tendency towards allergic (atopic) diseases such as eczema, asthma and rhinitis. Lactobacilli are also needed for optimum health in the female reproductive tract and may help to reduce the risk of developing candida (thrush) infection and bacterial vaginosis - a common condition in which healthy lactobacilli are severely depleted within the female tract. Interestingly, recent research suggests probiotic bacteria may even have a beneficial effect on the circulation, helping to reduce excessive blood stickiness and lowering raised cholesterol levels. This is probably because they produce short-chain fatty acids which are absorbed from the colon and transported straight to the liver, where they have a positive effect on fat metabolism.

Dietary sources include live bio-yoghurts, fermented milk drinks and such supplements in tablet or capsule form. While probiotic dairy and juice-based drinks are ideal for children, and make a popular addition to school lunch-boxes, many adults prefer to take their probiotics in supplement form. These contain ´freeze-dried´ probiotic bacteria which, although alive, are essentially held in suspended animation. Such supplements have the advantage of being dairy free and virtually calorie-free as they do not have to provide the sugar needed to keep actively growing bacteria alive. More importantly, modern techniques mean they do not have to be kept refrigerated, making them especially useful for travelling abroad. Supplements also provide a guaranteed potency of live probiotic bacteria. In contrast, the active bacteria found in yoghurt and fermented drinks are fragile and, after a product has been kept in a fridge for several days or even weeks, it will contain less live bacteria than when it was freshly prepared. Capsules also tend to work out cheaper.

However you choose to obtain your probiotics, they should ideally be taken every day to replenish those naturally flushed from your body. There are no known problems associated with continuous treatment, even at high dose.

Replenishing your probiotic bacteria can improve your general sense of well-being as well as helping to maintain a healthy digestion, immune system and circulation. I firmly believe that everyone would benefit from taking probiotics, but they are especially helpful for those who:

• eat a nutrient-poor diet
• lead a busy, stressful lifestyle
• are currently on, or have recently taken, antibiotics
• suffer from intestinal problems such as irritable bowel syndrome, inflammatory bowel disease, chronic diarrhoea, diverticulitis, recurrent candida or other bowel problems
• are suffering with, or recovering from, a serious illness or surgery
• feel they have a reduced immunity, eg associated with recurrent infections
• are travelling abroad and therefore at increased risk of gastroenteritis

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