DOES IT WORK? Dónal Ó Mathúna looks at probiotics and intestinal problems.
PROBIOTICS HAVE quickly become very popular as "functional foods". These are foods alleged to have health-promoting or disease-preventing properties beyond their nutritional value.
Probiotic yogurt drinks are among the fastest-growing examples of these products. While your first encounter with probiotics may be among dairy products, most of the research has been conducted on capsules of the dietary supplement. Tablets, powders and supplemented drinks are also available.
Probiotics are used to promote a healthy balance of micro-organisms in our intestines. More than 400 different species of bacteria and yeast normally inhabit our gastrointestinal tracts.
A delicate balance exists between microbes that are beneficial and those that cause problems. This balance can be disturbed by illness, poor diet, stress, alcohol, antibiotics and other factors.
The most common symptom of imbalance is diarrhoea, but a variety of other stomach and intestinal problems can develop. Probiotics are believed to help restore a healthy microbial balance and inhibit disease-causing microbes.
There is clear evidence that some probiotics are beneficial. However, a huge variety of products is available with a vast range of doses. This makes it very difficult to give general recommendations about probiotics.
Some of the bacteria most commonly used in probiotics (either alone or in combination) are Lactobacillus species, Bifidobacterium species and Streptococcus thermophilus. A specific strain, Lactobacillus GG, has been the subject of a large number of studies and been shown to be beneficial in preventing and treating diarrhoea.
This strain seems to be particularly helpful for children. When this strain was given to children or adults at the same time as they received antibiotics, significantly less diarrhoea occurred. Probiotics also appear to help with the latest culprit in hospital-acquired infections, C. difficile.
Beneficial effects were also found in developing countries where diarrhoea is a life-threatening problem, especially for children. Visitors to these countries can also benefit from taking probiotic supplements. However, the benefits vary depending on which particular infectious agents cause diarrhoea in a location and which strains are present in the probiotics.
Probiotics are also commonly recommended for irritable bowel syndrome (IBS). This is a relatively common intestinal problem leading to a variety of symptoms including abdominal pain, bloating, flatulence and bowel movement difficulties.
In the US, only the common cold leads to more missed work days. Studies with probiotics have found that they can reduce some symptoms, particularly bloating, but not all. The results have not been consistent. The evidence of benefit for IBS is therefore much less clear-cut.
Studies with probiotics have not found them to be effective with more serious intestinal problems like Crohn's disease or to treat infections.
Probiotics are generally safe. A common side effect is flatulence, but that usually subsides after a few days.
The biggest risk with probiotics appears to be to your wallet. Large variation exists in the quality of products. The bacteria in probiotics must reach the intestines, but stomach acid kills many of them.
Therefore, large doses are needed, usually one to 10 billion bacteria per day. Independent studies of products found that more than one-third did not contain one billion bacteria per daily serving. Many did not contain what their labels claimed.
Probiotics can be beneficial for people with a range of relatively mild intestinal problems. They may be particularly helpful to take along with antibiotics if they tend to cause diarrhoea.
They might also be beneficial when travelling to countries where diarrhoea is common. However, there is no evidence that probiotics benefit healthy people and manufacturers have been criticised for advertising that implies they do.
Interest in probiotics is relatively new. Because of that, information on the best products to use or the best way to take them is often not available.
As a general approach to improving one's diet when intestinal problems have developed, probiotics are well worth trying.
However, they should be used on a trial basis and not taken indefinitely to avoid unnecessary expenditure. There is limited information available on using probiotics to treat specific conditions.
However, as more research is conducted, it is likely that such guidelines will become available relatively soon.
Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
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