Weighing up Probiotics

• Posted On: 27/05/2010 18:00:00
• In: General

Probiotics are the 'good' bacteria that we're told can tackle everything from irritable bowel syndrome to colds and flu. And with nearly 60 per cent of UK households now regularly buying probiotic yoghurt drinks, it seems we have really bought into the idea that these friendly bugs can do us the power of good.  But do probiotics - and the related prebiotics - really offer the many health benefits that manufacturers would have us believe? We look at the evidence.

HOW THEY WORK:

As well as lacing dairy drinks and yoghurts, probiotics - or friendly gut bacteria - crop up as addtions to multivitamin formulations and as supplements in their own right. We already have around 100 trillion equivalent to 1.5kg - bacteria resident in our gut, so it might seem unnecessary to consume any more. But the theory is that in doing so, the good type will outweigh the bad, and our digestive and immune health will be stronger.

Ideally, 70 per cent of the bacteria in our gut should be 'probiotic', with only 30 per cent being less desirable species such as E. coli or salmonella. However, the balance can be tipped the other way by illness, poor diet, stress, the effects of age on our gut flora, or the use of antibiotics.

Two of the most beneficial probiotic families are Lactobacilli and Bifidobacteria. Taken daily, they can crowd out bad bacteria while you are taking them, reducing your risk of stomach bugs, food poisoning and other gut ailments.

IMMUNE BOOSTERS:

According to Professor of Food Microbiology at Reading University and a leading authority on gut bacteria, there's also good evidence that they may help our immune defences.

'Around 60-70 per cent of our immune system is in our guts,' he explains. 'We're discovering that some probiotics may stimulate cells of the gut immune system, possibly causing them to secrete molecules, which can then enter the bloodstream and improve our defences to various ailments, including colds and flu.'

WHAT ARE PREBIOTICS:

Prebiotics aren't in themselves bacteria, but they can increase the number of beneficial bugs in your gut by feeding those already established there. 'Prebiotics are plant fibres such as fructo-oligosaccharides and inulin, which act as a food source for probiotics, helping them to proliferate substantially' explains Professor Gibson.

Prebiotics occur naturally in foods such as leeks, onions, bananas and chicory, but most experts agree that it's impossible to get high enough levels to cause significant gut flora changes through diet alone. Some cereals and breakfast bars have prebiotics added, and they come in powder, pill and capsule form too.

THE EVIDENCE:

Despite the growing popularity of probiotics, scientists at the European Food Safety Agency recently rejected 10 claims for probiotics outright and said a further 170 had not provided enough evidence of their effects. But while there may be many overblown and non-validated claims for probiotic benefits, there's convincing evidence that the right products will do us good,' according to Professor Gibson.  He says: 'An effective product should minimise the effects of gut infection, and benefit people travelling abroad and coming in to contact with different bacteria that might upset their system.' What's more, he adds: 'They are also useful for people taking antibiotics (which kill good bacteria as well as bad), and for those going into hospital where gut infections are rife.'                                                                                  

THE FUTURE: 

Prebiotics have not been as well researched as probiotics, but there is growing evidence that they are useful for a sluggish gut. The bacteria they boost - the Bifidobacteria family - help boost - the Bifidobacteria family - help to bulk out stools, easing constipation and bloating, particularly when these symptoms are associated with an irritable bowel. And because they boost resident bacteria, their effects may last longer.

'In the future, prebiotics may prove to be more reliable way of making beneficial changes to gut flora,' says Professor Gibson. 'That's because they can change flora longer term, whereas the action of probiotics is always transient.' But though their theoretical benefits seem clear, there's still a lot we don't know about how particular strains and blends of probiotic bacteria work - in particular strains and blends of probiotic bacteria work - in particular how genetic differences might affect how they work in one person versus another.

A huge scientific project is now under way to identify all the different bacterial strains living in the human gut.

We should be able to use probiotics much more effectively once scientists have finished this, but for now, exactly which species of bacteria are best in which situation and the dosage needed, is an area filled with uncertainty.

If you're healthy and free of digestive ailments, you probably don't need probiotics. If you could benefit from them, you may need to try various products, which could be yoghurts, probiotic drinks, fortified foods or supplements, to find what suits you best.

'It's unlikely you'll ever do yourself any harm from taking probiotics,' says Professor Gibson. 'And given that gut problems are so rife due to our modern lifestyles, most people will generally benefit.'

PICK AND CHOOSE:

• Stick to bacterial strains that start with the names Lactobacillus of Bifidobacterium. Other bacteria, including yeasts and cocci, can be called 'friendly', but their effects are less proven.
• A product should have a minimum of 10 million bacteria per dose. If it doesn't state the bacterial count, check with the manufacturer or don't buy it.
• For gut benefits, try a probiotic containing largely Bifidobacteria.
• For immune-enhancing effects (including colds) go for one containing Lactobacilli or  Lactobacilli and Bifidobacteria.
• A good probotic will also contain at least 2g of prebiotic.
• If you take a prebiotic on its own (without a probiotic element), you need at least 5g a day.