Does it matter where you get your daily dose of probiotics—in food or a supplement—as long as you get them? The answer, according to two new studies, is a resounding yes.
Probiotics are living bacteria and yeasts that offer a variety of health benefits, especially for the digestive system. They’re available in yogurt and a variety of other fermented foods and beverages as well as in nonfood supplements.
Until now, little has been known about how the products containing those probiotics might influence their effectiveness—and if there something about dairy products that makes them particularly effective.
“Taken together, our findings indicate that the manner in which a probiotic is delivered—whether in food or supplement form—could influence how effective that probiotic is in delivering the desired health benefits,” says Maria Marco, associate professor of food science and technology at University of California, Davis.
In two preclinical studies, researchers examined the performance in the intestine of Lactobacillus casei, one of the most common probiotics, frequently found in yogurt and other dairy foods that has been shown to be helpful in preventing a host of digestive problems ranging from diarrhea and lactose intolerance to more severe, chronic disorders including inflammatory bowel disease, or IBD.
While dairy foods such as yogurt are often used to deliver probiotics commercially and in clinical research trials, it has been unclear exactly why dairy products are preferred over other foods and beverages or nonfood supplements, Marco says.
Two suspected benefits were the dairy carbohydrates that support the growth of the probiotics and the potential for dairy foods to buffer the probiotics from exposure to acidic conditions in the stomach.
Probiotics in Milk
In the first of the two studies, published in the Journal of Proteome Research, investigators tested whether the low temperatures at which dairy foods are stored might better prepare the probiotics to survive and function in the intestine. They compared how a particular strain of L. casei, allowed to incubate in refrigerated milk, persisted in the intestine compared to when that probiotic was delivered in milk without the cold-temperature incubation step.
The researchers found that 205 L. casei proteins were produced either at higher levels or exclusively when the probiotic was allowed to incubate in refrigerated milk, and that these proteins, which were produced before the dairy product was even consumed, were key to survival of L. casei in the digestive tract.
In the second study, published in the journal Applied and Environmental Microbiology, the researchers compared L. casei delivered in milk to milk alone and to L. casei delivered in a nonnutritive, buffered medium, in terms of the effectiveness in preventing symptoms of IBD in mice.
They discovered that mice fed L. casei in milk exhibited fewer symptoms of IBD than did mice fed milk alone or the same probiotic strain in a nonfood supplement format.
They also demonstrated that mutant forms of L. casei, which were unable to produce certain milk-based proteins, were unable to prevent the disease, further underscoring the importance of the dairy-based delivery system for this probiotic.
“We are now beginning to understand the concise mechanisms by which probiotic bacteria benefit human health,” Marco says. “These findings are pivotal to understanding the conditions in both the food product and the digestive tract that influence the effectiveness of the probiotic, and they really point to the need now for similar studies with humans.”