Probiotics help distance runners stay healthy

By Anne Harding

NEW YORK (Reuters Health) - Endurance runners' strenuous training can erode their immunity and make them more vulnerable to catching colds, but a daily dose of "good" bacteria could bring their immune systems back up to speed, Australian researchers have shown.

These bacteria, known as probiotics, are found in fermented dairy foods like yogurt, and are also available as dietary supplements.

"There is emerging evidence that probiotic supplementation can improve the health of a wide range of individuals including infants, athletes, people in highly active and/or stressful jobs, and in the general population," Dr. David Pyne of the Australian Institute of Sport in Canberra, one of the study's authors, told Reuters Health.

To investigate whether the supplements help endurance athletes stay healthy, Pyne and his team randomized 20 healthy elite distance runners to take a capsule containing Lactobacillus fermentum or a placebo every day during their four-month winter training session. The athletes ran about 100 kilometers (62 miles) per week, on average.

As the researchers report in the British Journal of Sports Medicine, runners who took probiotics averaged 30 days of respiratory symptoms during the course of the study, compared to 72 days for those on placebo.

Probiotic treatment also doubled levels of interferon gamma, a substance secreted by T cells that plays a key role in fighting viral infections.

"Probiotics primarily work by providing good bacteria in the gut to maintain a healthy balance in the digestive tract and stimulating the immune system," Pyne noted. "In effect, probiotics top up the beneficial bacteria in the gut to improve the balance between good and bad bacteria." This better balance may improve mucosal immunity, or the ability of cells in the body's mucous membranes to fight off infection, throughout the body, he added.

While probiotics clearly benefit a wide range of individuals, including recreational athletes as well as elite competitors, they can't replace "a healthy, well-balanced diet, regular exercise, and good hygiene," Pyne said. To get the most out of probiotic supplements and foods, which can degrade over time, "consumers should purchase products and supplements from reputable manufacturers and ensure that use-by-dates are adhered to," he added.

SOURCE: British Journal of Sports Medicine, February 13, 2008.