What are probiotics?
Probiotics are living organisms that, when ingested in sufficient quantities, provide health benefits beyond basic nutrition. They're often referred to as "friendly," or good, bacteria.
Edward Farnworth, a senior research scientist for Agriculture and Agri-Food Canada, says that some strains of probiotic bacteria can kill the disease-promoting bacteria that live inside our intestines. During the time that the probiotic bacteria pass through the digestive system, they also release chemicals to communicate with the intestines. "As the probiotics go through, they're communicating with the intestinal wall, and the cells in that intestinal wall are starting all kinds of protective mechanisms for disease resistance and infection," says Farnworth.
Who should take probiotics?
Probiotics are recommended for people who take antibiotics, are under stress or are travelling. Stress can upset your stomach and alter the microflora in your gut, says Lisbeth Truelstrup-Hansen, the coordinator of the food science program at Dalhousie University in Halifax. "When you travel, you're bombarded with new organisms that your body isn't really balanced out to accept," she says, and probiotics can help stabilize your gut microflora.
The probiotics in yogurt may also help make the diarrhea caused by some antibiotics less severe and shorten its duration, says Farnworth, because the active cultures help replenish beneficial bacteria, returning colon function to normal.
Do all yogurts contain probiotics?
Gregor Reid, director of the Canadian Research and Development Centre for Probiotics, and one of the specialists responsible for helping develop World Health Organization (WHO) guidelines for probiotics, says consumers have to be aware that until a manufacturer has tested a yogurt product in human trials, there is no way to be sure it confers any additional health benefit beyond "replenishing the organism's beneficial bacteria inside of you." Health Canada does not currently enforce WHO guidelines, and the only yogurt that has been tested in human clinical trials in Canada is Danone Activia, notes Reid. Until products are tested in human trials, he says, they shouldn't be called probiotics.
Each strain of bacteria can have a different effect. One probiotic may help with diarrhea, says Farnworth, while another may boost the immune system or help with urinal-genital tract infections, but the health benefits they confer vary. At this point, he says, it isn't possible to tell consumers which strains to look for on the label, but the more types of probiotics a yogurt contains, the better the chance it will have positive effects. "Consumption of probiotics in general is healthy for your digestive system, and I think people find that when they consume these products."