Adding prebiotics to formula may benefit baby's brain.
Anyone who has had children will have heard the phrase "breast is best." This is a given, but, for a wide range of reasons, not every mother can breast-feed their baby.
For this reason, it is important that infant formula provides the best start in life and mimics the incredible capabilities of breast milk as closely as possible.
Already, infant formula is a good substitute, but there is always room for improvement when you are competing against Mother Nature.
Breast milk naturally contains prebiotics, which are small, indigestible fiber molecules; they provide a welcoming environment for gut bacteria.
Having the gut colonized by bacteria early in life is important for the developing immune system and helps prevent infections. Also, studies have shown that adding prebiotics to infant formula can help improve intestinal function and reduce allergies.
A recent study from the University of Illinois' Piglet Nutrition and Cognition Lab investigated what effects adding prebiotics to infant formula might have on pigs. Specifically, they wanted to know whether it would enhance memory and exploratory behavior.
Why study pigs?
Using rats and mice to investigate drugs or biological mechanisms is a well-known and incredibly useful method. However, piglets are more similar to baby humans than rodents are. Their behavior, their digestive systems, and even the way their brain develops are much more similar to us than we are to rats.
Although adding fiber to a piglet's diet to alter the workings of the brain might seem strange, evidence is already mounting that our gut bacteria play an influential role on our mind and mood.
One of the researchers, Stephen Fleming, says, "There hasn't been a lot of work looking at the gut-brain axis in humans, but a lot of rodent work is showing those connections." For instance, in one study, rodents fed prebiotics shortly after birth displayed increased positive social interactions and improved memory.
"This is taking it to an animal model that is a lot closer to human infants and asking if that connection still exists and if we can tease out possible mechanisms."
Stephen Fleming, lead author
The latest study, published in the journal Nutritional Neuroscience, follows on from research by the same scientists in 2016. In their earlier paper, they concluded that adding new ingredients to formula, including prebiotics, might influence brain development and behavior.
Piglets and infant formula
For the new research, 2-day-old piglets were fed infant formula based on cow's milk supplemented with galactooligosaccharide (GOS), a naturally occurring prebiotic, and polydextrose (PDX), a synthetic carbohydrate with prebiotic activity.
When the piglets were 25 days old, they were put through their paces in a range of learning, memory, and stress tests. After 33 days, blood, brain, and intestinal tissue was collected for examination.
To test their memory, the scientists used a "novel recognition test." The pigs were given dog toys to play with; they received a brand new toy and one that they had seen before. If the pig spent more time with the new toy, it was taken as an indication that they recognized it as new and, therefore, preferred it.
Fleming explains why this type of test is useful:
"If you're trying to test for memory, this test is closer to what we'd do with an infant. After all, we don't generally train infants on mazes. We know from previous research this test works for pigs, but this is the first published example of using it in a nutrition context."
They found that pigs who received the PDX- and GOS-enhanced formula spent more time playing with the new toy than those that received standard formula. This was taken to mean that the brain was healthy and learning and memory was improved.
Did the prebiotics make a difference?
To find out whether the prebiotics were having an effect on gut flora, the researchers tested for volatile fatty acids (VFA). Bacteria excrete VFA's as they digest prebiotics, so increased levels indicate increased numbers of bacteria.
As expected, in the pigs that were fed PDX and GOS, VFAs were increased in the blood, brain, and colon. It is possible that VFAs could be involved in gut bacteria's influence on our brain and behavior.
However, in the current study, the expected change in stress-related behavior was not found; despite measuring changes in VFAs, no connection was seen in behavior.
The researchers were also surprised to find that, in the pigs fed the prebiotic, serotonin levels in the hippocampus went down.
"When you hear less serotonin, there's an immediate reaction to say, 'Well, that's bad,'" Fleming says. But that's not necessarily the case; the pigs didn't display any greater anxiety during stress tests, for instance. This drop in serotonin may have been because of reduced levels of tryptophan, the precursor of serotonin. More research is needed to explore this further.
Although the study could not find an alteration in behavior, they did show that the pig's memory was improved by prebiotics. As part of the growing evidence of gut bacteria's impact on brain function, the results make an interesting read.
"There are so many ways we can alter the composition of the microbiota and they can have very strong benefits. Promoting good 'gut health' remains a strong focus in the field of nutrition," says study co-author Ryan Dilger, associate professor in the Department of Animal Sciences at the University of Illinois in Chicago.
As Dilger says, there is a great deal of interest in gut bacteria's influence on the brain. More work is sure to follow in hot pursuit.