Millions of people take probiotics to treat and prevent a number of medical disorders. Probiotics have been claimed to treat a wide variety of medical ailments. However, for most of the medical disorders, the evidence for probiotics in fighting diease is scant.
Now there is some evdience that daily intake of probiotics can help fight upper respiratory tract infections. The latest analytical review of several large studies by Dr. B. Dong from Sichuan University in China, indicates that taking prophylactic doses of probiotics in yogurt or other supplements is associated with a lower incidence of respiratory tract infections. In addition, people who took probiotics also required less medications when treating their symptoms (1).
While this evidence is not very strong, Dr. Dong claims that there certainly does appear a trend that probiotic usage on a daily basis may have some protective benefits against upper respiratory tract infections. The major side effects of probiotics were stomach upset and excess gas. This study only looked at young people.
Previous data also support the use of probiotics for the treatment of infectious diarrhea and vaginal infections during pregnancy.
Dr. Dong believes that probiotics which contain the lactic acid bacteria and bifidobacteria may help boost the immune system in the gut and also improve the integrity of the intestinal wall.
Similar studies on elderly people have not shown a reduction in the common cold but the duration of the infection has been shortened. More important, the risk of getting really sick was also much lower in people taking probiotics. (2)
At the moment it is not known how long the benefits of probiotics last if the supplement is stopped.
In any case, for consumers who are prone to the common cold (URI) and do not like taking medications, probiotics are an option. These health supplements are relatively cheap, safe and come in a variety of flavors. In my opinion the only sure way to know if these products lower the frequency of the common cold, is to try them out.