Do you think all yoghurts are pretty much the same? Well, have we got news for you. Yoghurt is a handy, low fat, nutritious snack - and now it is even better than ever

You have probably seen 'live' yoghurt or 'bio-active' yoghurt advertised on TV or sitting in the chilled section of your local supermarket - well, now might just be the time to try them.

For thousands of years, yoghurt has enjoyed a rich tradition of being a healthy food. It has been suggested, for example, that it can increase your life span. Scientific interest began in the early 1900's with the work of the Nobel Prize-winning biologist Elie Metchnikoff at the Institut Pasteur in Paris, but it has not been until the past twenty years that interest has really taken off.

Yoghurt is made by a living culture fermenting milk to produce yoghurt as we know it. The culture is one of the essential ingredients in yoghurt - in fact, yoghurt wouldn't really be yoghurt without it.

Cultures are composed of unique living micro-organisms and common cultures are used in all yoghurts, but some yoghurts may also contain additional cultures, such as Lactobacillus casei Shirota, L. casei Immunitas or Bifidobacteria - these are the ones we know as probiotic yoghurts.

Probiotics are naturally occurring, live bacteria, added to some foods to help replenish levels of good bacteria that occur naturally in the gut. Specific strains of probiotic bacteria, such as L. acidophilus, L. casei and B. bifidus, can help to prevent the growth of 'unfriendly' bacteria. Probiotic foods mainly include dairy foods, but probiotic bacteria are also available in the form of tablets and powder.

Prebiotics act slightly differently, by nourishing the bacteria that are already present in the digestive system. They often go hand-in-hand with probiotics as they create a hospitable atmosphere in the gut for probiotic bacteria to grow and thrive. The most common prebiotic, inulin, is found in garlic, onions, artichokes, bananas and wholegrains.

More research is needed into the beneficial effects of pre- and probiotics on health, but a number of studies have already shown benefits believed to be associated with pre- and probiotics, including:

• Improved digestion
• Increased immunity from infectious disease
• Lowering of blood pressure and blood cholesterol
• Replace beneficial bacteria after a course of antibiotics
• Prevention of candida

There have been some questions about how probiotics can benefit healthy people, and whether they actually reach the intestine in sufficient amounts to be beneficial. So for maximum effect, it's best to take prebiotic and probiotic supplements, although there is certainly no harm in taking foods containing them, such as probiotic drinks, yoghurt and breakfast cereal. These foods taste just as good as those without pre- or probiotics added so you won't notice a difference!

Here are some of the most worthwhile supplements and foods available:

Probiotic

• Seven Seas Multibionta - independent tests have shown that this supplement is one of the few that does what it says on the label. It is enteric coated to protect the ingredients during their passage to the gut and can therefore deliver the promised amount of probiotics.
• Solgar ABC Dophilus powder for kids under 4, Advanced Acidophilus Plus for kids over 4, and Advanced 40 Plus Acidophilus for adults over 40 - all enteric coated and available from Nutricentre or health food stores.
• There is a wide range of probiotic drinks and yoghurts available including Tesco own brand and other well known brands. It's important to bear in mind that probiotic and prebiotic drinks can be quite high in sugar, so compare brands to find those lowest in sugar.

Prebiotic

• For a good prebiotic, try fructo-oligosaccharide (FOS) sold in powdered form or tablets. Can be added to smoothies and cereal. Available as above.
• Prebiotics are also found in Muller Vitality Yoghurt Drinks and Kellogg's Rice Krispies Multigrain.