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A University of Toronto study, the first of its kind, reveals that not all probiotic yogurts are created equal.

While all probiotic yogurts support intestinal health, a study of common supermarket yogurts marketed for their probiotic health properties, found that products could offer a variety of additional health benefits not advertised on their label. However, in many cases the dosage of probiotics in these products are too low to offer the health benefits found in clinical trials.

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“Most people don’t realize that different products contain different types of probiotic bacteria and therefore may offer different health benefits,” says Mary Scourboutakos, a postdoctoral researcher who co-authored the study along with Assistant Professor Elena Comelli and Professor Mary L’Abbé, chair of the Faculty of Medicine's department of nutritional science. “Our study showed there’s a gap between the health benefits found in clinical trials and the benefits that consumers can expect to receive from the probiotic food products in the marketplace.”

Probiotics are “good” bacteria that survive digestion and reach our intestines. All probiotic yogurts are healthy because these good bacteria support the intestines, aid digestion and crowd out harmful bacteria in the gut. Currently, Health Canada requires that products labelled as “probiotic” contain at least one billion per serving.

“Products are meeting the minimum standards to be called probiotics but we found that with higher doses some products could be doing much more,” says Comelli.

Probiotics are one of the fastest-growing product markets globally. Emerging research has shown probiotics can improve conditions such as irritable bowel syndrome (IBS) and decrease risk for the common cold. But not all yogurts contained the strains that help with these specific conditions. And sometimes, yogurts that contain these strains have dosages that are up to 25 times lower than has been found to be effective in clinical trials.

The researchers found that the strain Bifidobacterium lactis DN-173 010 contained in Dannon’s Activia has been shown to improve regularity as well as decrease stomach pain and bloating in individuals with irritable bowel syndrome. But they found that two to 25 servings of this yogurt per day may be necessary, depending on the condition being addressed.

Another common brand, DanActive, contains the Lactobacillus casei DN 114-001 strain, which helps decrease the frequency and length of the common cold and the flu. In this case, two servings per day are needed to achieve these effects.

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

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

But none of the yogurt brands makes these other health claims. In Canada, food labelling laws prevent them from doing so. Consumers looking for protection against specific conditions would have to research which strains help, and then search yogurt labels to find those strains. The research shows that more specific probiotic labelling laws could help consumers make more informed choices.

Scourboutakos noted that kefir (fermented milk) products in the study (produced by Liberté and Iogo) had the greatest variety of different types of probiotic bacteria (sometimes greater than 10) and often contained the highest dosage. While there were no studies testing the particular combinations of strains found in these products, some research suggests that products with a larger number of strains (such as these kefirs) may have greater health benefits compared to products that only contain one or two strains. The study results underscored the lack of research on probiotic foods.

The researchers focused on the most common supermarket brands, and did not study health-food store yogurts. To receive benefits, probiotics need to be consumed regularly because these bacteria are constantly passing through the body.

Comelli has received funds from a probiotic company to support her research, but the company was not involved in this study.