Sweet support for beneficial probiotic cultures in yoghurt

Adding a spoonful of honey to plain yoghurt supports the probiotic cultures in the fermented dairy product, according to two studies from the University of Illinois Urbana-Champaign.

Greek yoghurt and other yoghurts contain probiotic strains such as Bifidobacterium animalis (B. animalis) in addition to conventional yoghurt starter cultures.

Hannah Holscher, associate professor in the Department of Food Science and co-author of the two studies, which are both published in The Journal of Nutrition, said: “The enzymes in our mouth, stomach and intestines help with digestion and facilitate nutrient absorption, but they also reduce the viability of microbes. That’s great when it’s pathogens but not necessarily when it comes to beneficial bacteria.

“We wanted to see if honey could help probiotic bacteria survive in the gut.”

In the first study, Honey Varietals Differentially Impact Bifidobacterium animalis ssp. lactis Survivability in Yogurt through Simulated In Vitro Digestion, the researchers conducted a laboratory experiment where they tested the effect of four different kinds of honey (alfalfa, buckwheat, clover and orange blossom) on the viability of B. animalis in yoghurt through simulated digestion processes. They grew microbes in petri dishes with solutions that mimicked the composition of saliva, stomach acid, intestinal bile and enzymes.

For the saliva and stomach fluids, there were no differences in B. animalis survival between any of the honey varietals and control treatments of yoghurt mixed with sugar or water. However, yoghurt with honey, particularly the clover type of honey, helped support the survival of probiotics in the intestinal phase of digestion.

Next, the researchers wanted to test their findings in a second clinical study entitled Honey Added to Yogurt with Bifidobacterium animalis subsp. lactis DN-173 010/CNCM I-2494 Supports Probiotic Enrichment but Does Not Reduce Intestinal Transit Time in Healthy Adults: A Randomized, Controlled, Crossover Trial. The researchers recruited 66 healthy adults and asked them to consume two different items for two weeks each — yoghurt with clover honey and pasteurised, heat-treated yoghurt. The participants provided stool samples and information about their bowel movements. They also filled out questionnaires and completed tasks evaluating their mood, cognition and overall wellbeing.

“Our findings showed that pairing honey with yoghurt supported the survival of the yoghurt’s probiotic bacteria in the gut, so the lab study results did translate to real-world application in humans,” Holscher said.

However, there were no changes in intestinal transit time, bowel movement frequency or any of the mood and cognition measures. Holscher said this is likely because the participants already were healthy adults with regular bowel movements, so there wasn’t a lot of room for improvement.

The researchers also conducted a smaller follow-up study with 36 participants who consumed a third food item, yoghurt with sugar. When the researchers compared the results of all three conditions, the combination of yoghurt with honey preserved the most probiotics, but there were no effects on the health measures.

“We found that one tablespoon of honey in a serving of yoghurt helps support probiotic survival. However, we have to keep in mind that honey is an added sugar, and most Americans need to be cognisant of the amount of sugar in their diet to maintain a healthy body weight,” Holscher said.

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