Most probiotic yogurts don't contain enough 'good' bacteria for additional benefits: study

CTV National News: Probiotics debunked Vanessa Lee reports on a close look by scientists at the dose of probiotics in yogurt and whether it's beneficial to consumers.

Lots of popular yogurts contain probiotics linked to all kinds of health benefits, but a new Canadian study finds that most of those products don’t have anywhere near enough of the “healthy bacteria” to do much good.

The new study by nutritional science researchers at the University of Toronto finds that the dosage of probiotics in most widely-available yogurts are too low to offer the health benefits seen in clinical trials.

Probiotic yogurts have become hugely popular in light of research that found the types of “good” bacteria contained in these products can help aid digestion and crowd out harmful bacteria in the intestines.

Some studies have found the bacteria can reduce flatulence, stomach discomfort, diarrhea caused by the use of antibiotics -- even the bacteria that cause cavities.

But Mary Scourboutakos, a postdoctoral research associate who co-authored the study along with professors Elena Comelli and Mary L’Abbe, says their study found that the probiotic levels in these yogurts were sometimes up to 25 times lower than what clinical trials have found to be effective.

“What we found is that all probiotic food products offer certain general benefits,” Scourboutakos told CTV News Channel Wednesday. “The caveat here is that often, the dosage that’s being tested in these clinical trials is higher than the dosages found in the products.”

Health Canada requires that products labelled as “probiotic” need to contain at least one billion bacteria per serving. But food labelling laws prevent the products from making any health claims about the probiotics.

Each brand of yogurt the Toronto team studied contained different types of probiotic bacteria, each linked to different health benefits. But the study found most brands don’t contain enough to offer those benefits.

For example, Dannon’s Activia contains Bifidobacterium lactis DN-173 010, which has been shown in lab studies to improve regularity, as well as decrease stomach pain and bloating in those with irritable bowel syndrome. But the researchers found that it would take two to 25 servings of the yogurt per day to achieve the effects observed in clinical trials.

Another common brand, DanActive, contains Lactobacillus casei DN 114-001 strain, which studies show helps decrease the frequency and length of the common cold. But at least two servings per day would be needed to achieve these benefits.

Yoptimal contains Bifidobacterium lactis BB12+ and Lactobacillus acidophilus LA-5, which decrease cavity-causing bacteria and may improve glycemic control and cholesterol levels in diabetics. One-half to two servings per day would be needed.

BioBest also fights the common cold, but, 20 servings a day would be needed to achieve the effect observed in clinical trials.

The team also looked at kefir products by Liberte and Iogo, which are a kind of drinkable, sometimes effervescent fermented milk. They found these products often contained the highest dosage of probiotic bacteria. They also had the greatest variety of different types of bacteria -- sometimes as many as 10 strains.

However, the particular mixtures of bacterial strains in these kefirs have not been studied, so it’s hard to determine what health benefits they might offer.

But the study’s findings don’t necessarily mean that consumers should give up on probiotic yogurts and kefirs.

Scourboutakos said there’s agreement among scientists that the more good bacteria there is in your gut, the harder it is for bad bacteria to flourish and cause problems. She suggests looking for probiotic products that have at least 10 billion bacteria per serving.

“People have been eating bacteria for thousands of years,” she said. “If you look around the globe, every region has some sort of fermented food that would have given them these bacteria.”

In Germany, for example, that food is sauerkraut and Koreans have enjoyed the bacterial benefits of kimchi for generations, she added.

The researchers focused on the most common supermarket brands, and did not study health-food store yogurts. It should also be noted that Comelli has received funds from a probiotic company to support research. The company was not involved in this study.