What are probiotics? Also known as “good bacteria,” probiotics are bacteria that are the same or similar to those found naturally in the human body. Advertised to help a variety of health conditions or to prevent food allergies, but despite claims on product packaging, the U.S. Food and Drug Administration (FDA) has not approved probiotics for the treatment of any disease. That is not to state, however that there are no scientific studies demonstrating health benefits of probiotics.
Probiotics are often used for the treatment of diarrhea. In a Cochrane review published this year, of 23 trials examined, with over 4000 participants studied, probiotic use reduced the risk of developing antibiotic-associated diarrhea by 64%. In a recently published 12-week study in the treatment of diarrhea from irritable bowel disease/irritable bowel syndrome, however, there was no significant difference in diarrheal symptoms between those patients with IBS who consumed probiotics compared to those who did not.
Probiotics may help prevent eczema or food allergy. In a study published last year in the Journal of Allergy and Clinical Immunology, women with a history of allergies who took probiotics during pregnancy or while breast feeding had a significantly reduced incidence of infant eczema (30% versus 79%). In a meta-analysis of 23 randomized, placebo-controlled studies, the majority (60%) had a decreased risk of eczema associated with taking probiotics (Current Opinion Allergy Clinical Immunology, 2013).
Probiotics plus anti-histamines given to children may ease the symptoms of allergic rhinitis (J. Pediatric Otorhinolaryngol 2012).
Probiotics may have direct effect on brain activity. In a study published earlier this year (Gastroenterology, 2013), researchers found evidence of changes in brain activity on functional MRI in women regularly taking probiotics. In a separate study, probiotics taken by patients with cirrhosis of the liver had a beneficial effect for preventing the first episode of hepatic encephalopathy.
Data on the efficacy of probiotics on reducing cholesterol levels reveal conflicting results (Clinical Lipidology, 2012).
Patients who receive probiotics before and after surgery for colorectal cancer had fewer post-operative infections, according to a study published from China (American Journal of Clinical Nutrition, 2012). These findings have not been confirmed by other studies in the U.S.
Recently published research examined the effects of probiotics on atopy (predisposition toward developing certain allergic hypersensitivity) risk reduction and asthma prevention in children. Published in Pediatrics, the authors performed a meta-analysis of randomized, placebo-controlled trials on the effect of probiotics in children. This study found that prenatal and/or early-life probiotics reduces the risk of atopic sensitization and total IgE (allergic immunoglobulin) but may not reduce the risk of asthma.
In summary, probiotics may help with antibiotic associated diarrhea, eczema in infants, or allergic rhinitis. They also appear to have effect on brain activity and may help prevent hepatic encephalopathy in patients with liver cirrhosis. The data are inconclusive whether probiotics can help with cholesterol levels or reduce infection rates after surgery. Probiotics reduce the risk of atopic sensitization but have not been shown to reduce asthma in children. In general, probiotics are safe, with few side effects.