Priobiotics: the 'friendly bacteria'

What are probiotics?

They're better known as 'friendly' bacteria. The smooth functioning of your gut depends on them. Since antibiotics, other drugs (including booze), stress, pollutants and processed foods can all reduce the level of friendly bacteria, the theory is that you should take probiotics to replace them.

Common probiotics include various species of the bacteria Bifidobacterium and Lactobacillus.

Do they work?

In theory, yes. In 2005 the National Center for Complementary and Alternative Medicine (NCCAM), the US government's lead agency for scientific research on complementary and alternative medicine and the American Society for Microbiology held a conference on probiotics. They concluded that they may be helpful to treat:

diarrhoea
infections of the urinary tract or female genital tract
irritable bowel syndrome
some intestinal infections.

Probiotics The evidence for diarrhoea is the strongest. For example, an analysis published in 2006 (in the Canadian Medical Association Journal) of six studies, involving 836 children on antibiotics showed that those who also took a probiotic had far less diarrhoea than those who just took the antibiotic.

How do you take them?

You can take them as supplements in a freeze-dried form or in probiotic-fortified foods.

So they work in theory. What about practice?

The market in probiotic drinks and yoghurts is now worth, according to The Guardian, over 300m a year. However, research reported in the paper in August 2006 suggested that half of these products either did not contain the right bacteria or did not contain enough to have any effect (although well-known brands such as Activia, Immunitas, Digestivas, Yakult, Actimel, Vitality, and the tablet Multibionta were deemed OK).

The big question — as for so many food supplements - is whether taking probiotics in the form of supplements is actually effective — ie do the probiotics actually get to the gut? Research commissioned by the Food Standards Agency in March 2005 suggested that many do not.

But Glenn Gibson, right, professor of Food Biosciences at Reading University who was involved in that research now says: 'Probiotics appear to work. The literature now cites over 100 human trials.

'Whether they'll actually reach your gut in sufficient quantity and quality to make any difference does depend on the type. Some products now use enteric-coating encapsulation to overcome the problems. For the yoghurts and drinks, it's harder to say. You can get high numbers of probiotics into a drink but the numbers reaching the gut do vary.

However, generally I am supportive of probiotics as the risk is negligible and advantages good.'