Although the full benefits of a regular intake of probiotics have not been completely determined the results of some published studies are interesting and compelling. Some of these studies certainly need confirmation in larger more scientifically robust studies before we can absolutely be sure of their specific roles for certain diseases. Most of the benefits of probiotics logically relate to the gut but more recently benefits are beginning to be realised for other areas of the body:

Potential benefits for the gut and digestion.

Travellers diarrhoea. Certain strains of probiotics have demonstrated positive results in treating diarrhoea and gastroenteritis commonly caught whilst travelling, usually from drinking water. In particular, a study published in the Journal of Pediatrics, concluded that Lactobacillus species are a safe and effective form of treatment for children with infectious diarrhoea. Other studies, have shown that prophylactic use of Lactobacillus containing probiotics significantly reduced the risk of nosocomial diarrhoea in infants, especially nosocomial rotavirus gastroenteritis.

Antibiotic induced diarrhoea. Antibiotics are obviously vital to kill unhealthy bacterial infection but, as a side effect, they also reduce the healthy bacteria in our gut altering natural balance of the microflora which can lead to bloating and diarrhoea. A report published in the Journal of Pediatric Gastroenterology and Nutrition showed that probiotics were helpful in the prevention or treatment of, antibiotic induced diarrhoea especially in children.

Bacterial food poisoning. Most acute diarrhea episodes are caused by viruses but some, especially those caught by ingesting infected food, can be bacterial. A study published in the prestigious scientific journal Proceedings of the National Academy of Sciences, found that probiotic bacteria can help protect against bacterial infection including Listeria and the super bug Clostridium difficile infection. Some Hospitals are giving people probiotics before going into hospital to reduce their risks of infection.

Chemotherapy induced diarrhoea. Some chemotherapy agents commonly cause diarrhoea due to damage to the cells lining the gut. If severe, as well as being very distressing and uncomfortable for the patient, this can lead to dehydration, concentration of the chemotherapy in the blood stream and eventually renal damage. A placebo controlled randomised trial from Helsinki involving 5FU chemotherapy for bowel cancer showed a highly significant reduction in the risk of diarrhoea. Other trials have reported benefits for analogues of 5FU such as capecitabine. Several ongoing trials are underway across the world including a large and significant one from Washington University School of Medicine

Irritable bowel syndrome (IBS) is a condition associated with abdominal bloating and flatulence. A 2010 Cochrane review summarised the evidence from clinical studies which showed that probiotics can help in some people. The National Institute for Health and Care Excellence (NICE) recommends taking them for at least four weeks, at a dose recommended by the manufacturer and if they work – continually.

Wheat and Lactose intolerance. As you get older it is common to develop an intolerance of gluten found in wheat and other grains. This causes IBS like symptoms with bloating and colicky pains. In the first instance it is advisable to reduce the intake of bread, pasta and cereals but a number of studies have demonstrated a helpful effect for probiotic intake. Intolerance to milk also is becoming more common, usually the result of a lactase deficiency. Lactase is an enzyme normally produced in your small intestine. It is needed to break down lactose and to enable you to digest milk. The probiotic Lactobacillus acidophilus helps with the digestion and absorption of lactose by producing lactase.

Potential benefits outside the gut.

Upper respiratory tract infections (colds). A study from Australia gave healthy athletes either probiotics or placebo. After one year the probiotic group had less colds and as a consequence had less disruption to their training. Athletes in Australia and across the world now take probiotics regularly. Several studies have shown that regular intake of live lactobacilli and bifidobacteria, shortened the duration and severity of upper respiratory tract infections. In 2011 a summary of all international studies was published in the prestigious Cochrane Database of Systematic Reviews, and concluded that probiotics also reduced the incidence of upper respiratory tract infections. The economic implications of these findings are enormous as the impact of colds is estimated to cost the United States $40 billion each year!

Bone health. There is a known link between chronic gut inflammation and bone, though it’s unclear exactly why. A laboratory study, involving mice, conducted by Scientists at Michigan State University was reported in the Journal of Cellular Physiology . It showed that just 4 weeks of probiotics significant increase in bone density. Experiments in humans have not been published yet.

Brain function. A study involving mice conducted by the Alimentary Pharmabiotic Centre in University of Cork showed that mice fed with Lactobacillus had significantly fewer stress, anxiety and depression-related behaviours than those fed with just broth. Moreover, bacteria fed mice had lower levels of the stress-induced hormone, corticosterone and had altered expression of receptors for the neurotransmitter GABA in the brain. In humans, a study from The University of California, showed that healthy women consuming probiotic-containing yogurt were reported to have improved brain function and less environmentally induced markers of stress.

Blood Pressure. There is emerging evidence that probiotics may have a role in cardiovascular health. A meta-analysis of nine studies, published in the journal Hypertension, tracked over 543 adults with both normal and high blood pressure and found that taking probiotics lowered systolic blood pressure by 3.56 mmHg and diastolic blood pressure by 2.38 mmHg, on average. The greatest effects were seen in subjects with BP above 130/85. And those who took probiotics with multiple strains were more successful at lowering BP than single-strain sources.

Fatty liver and metabolic syndrome. Too much fat accumulating in the liver affects its function, eventually leading to damage. Several factors can cause a fatty liver, defined as fat stores >10% of its volume, including obesity, diabetes, alcohol abuse, poor diet and genetic susceptibility. Although there are no significant studies in humans, researchers recently discovered that Lactobacillus and Bifidobacterium probiotic strains prevented the accumulation of fat in the liver of obese rats. Markers of inflammation (tumor necrosis factor and interleukin 6) and triglyceride counts also improved. In another animal study, mice were fed a high fat diet for eight weeks and given probiotics or placebo. Mice who received the bacteria ate significantly less than the control mice, had lower insulin levels and body fat, and reduced their fatty liver deposits. Trials in humans are planned.

Cholesterol levels. Research presented at the American Heart Association’s Scientific Sessions in 2012 reported that a formulation of Lactobacillus may be able to reduce blood levels of LDL (bad cholesterol).

Chronic Fatigue Syndrome. Scientists at University of Cork reported in the journal Gut Microbes that Bifidobacterium may have benefits for patients with chronic fatigue syndrome.

Bowel cancer. Preliminary experiments in animals found that a stimulated growth of bifidobacteria in the colon lead to the inhibition of colon carcinogenesis. The authors suggested that was attributed to the pH-lowering effect of bifidobacteria in the colon, which subsequently inhibited the growth of E. coli and clostridia. A decrease in growth of such pathogenic microorganisms also produce the modulation of bacterial enzymes that convert pro-carcinogens to carcinogens. In humans taking regular probiotics been linked to a lower rate of new polyp formation and bowel cancer relapse.


Prevention of irinotecan-induced diarrhea by probiotics: Randomized double-blind, placebo-controlled phase III study. J Clin Oncology. Mego M et al 32:5s, 2014 (s 9611).

Health claims substantiation for probiotic and prebiotic products. Sanders M, James T. Heimbach J, Bruno Pot B et al. 2011, Gut Microbes, 2 (3) pp 127-133.

Safety assessment of probiotics for human use. Sanders M, Akkermans L et al 2010 Gut Microbes, 1 (3) pp 164-185.

Probiotics: From Bench to Market. Annals of the New York Academy of Sciences (2010) Klein M, Sanders M, Duong T DOI: 10.1111/j.1749-6632.2010.05839.x

Guide to designing, conducting, publishing and communicating results of clinical studies involving probiotic applications in human participants. (2010) Gut Microbes Shane A, Michael D. Cabana M et al, Vol 1 (4) pp 243-253.

Food Formats for Effective Delivery of Probiotics. Annual Review of Food Science and Technology. 2009 Saunders M and Marco M. Vol. 1: 65-85.

How Do We Know When Something Called “Probiotic” Is Really a Probiotic? A Guideline for Consumers and Health Care Professionals (2009).

Probiotics: Their potential benefit to human health. Journal of the council for agriculture science and technology 2011 Saunders M, Gibson, Gill A. Oct 2011.

Use of probiotics in the management of chemotherapy induced diarrhoea – case study
JPEN J Parenter Enteral Nutr 2009. 33 (5) 569-70.