Back-Engineering Mother’s Milk

In a very small nutshell, back-engineering is the process of taking an object apart in order to learn how it was designed to do what it does. Increasingly scientists are taking this approach to substances and processes that occur in nature with the idea that the thousands of years of evolutionary tweaking that created them might yield better results than the human-engineered substitutes developed to accomplish the same or similar tasks. There’s a certain irony in this process because it often seems to occur after human attempts to reinvent nature’s various wheels sans this awareness fail for one reason or another.

An especially notable example of this is breast milk. While the gap between artificial milk replacers and the real deal often is presented as primarily a human issue, as our purebred domestic animal populations become more fragile and incapable of nursing their young, it seems likely that this may affect some animals too. Young animals separated from their mothers as soon as the young can eat solid food to expedite their sale or adoption seem like another population that could succumb to problems related to a lack of the beneficial components found in species-specific breast milk.

As scientists are discovering, breast milk is a lot more than liquid food. Among the naturally occurring substances in breast milk, one plays a role in the development of the gut’s immune response, while another one ties up iron which helps the body fight disease-causing microbes that need iron for their own survival. A third substance, lysozyme, is an enzyme that’s demonstrated the ability to kill enteropathic (i.e. pathogenic to the gut) E. coli in infected animals.

Another group of substances found in breast milk called oligosaccharides is especially intriguing for several reasons. These sugar molecules are among the most common solid components in breast milk, yet in spite of their numbers they’re not digestible. Did Mother Nature make some tragic mistake? Fortunately for the future health of many babies and adults, increasingly food chemists and bacteriologists are choosing to take an ecological view of their presence: If oligosaccharides are there, then they’re there for a reason. And more likely than not, it’s a good one.

Currently research explores the different ways these indigestible sugars indirectly or directly protect the gut. Some of these compounds apparently mimic normal gut cells enough that they fool harmful parasites into grabbing onto them instead of the host’s intestinal wall. Meanwhile others may actively encourage the growth of beneficial bacteria or reduce inflammation of the gut. Another group inhibits the growth ofStreptococcus pneumonia, a species commonly associated with ear and respiratory functions in human infants and youngsters. Yet another could prevent human infections with micro-organisms known to cause diarrhea in animals, such as Campylobacter and enteropathic E. coli.

As if all of this activity weren’t fascinating enough, breast milk offers yet another wonder. In an attempt to recreate the biology of the human gut as closely as possible, University of California at Davis scientist, David Mills, discovered that bacteria called Bifidobacterium infantis­ have a preference for a particular kind of oligosaccharide that’s commonly found in breast milk. He also discovered that certain bad bugs in the gut like to eat it, too. But given a sufficient population of B. infantis to snarf up these sugars first, the bad bugs can’t get enough to provide the energy they need to wreck their havoc on the gut. While this is important for all of us, it’s especially so for more vulnerable infants and toddlers for whom such infections may be life-threatening.

Naturally the studies involving animal models particularly interest me because of the increasing number of gut problems in companion animals. While there’s no doubt in my mind (even if others may not agree) that stress plays a critical role in this, does the fact that more animals may not have sufficient opportunity to nurse long enough contribute to this?

Going back to Bifidobacterium, many animals carry their own particular species of these bacteria. However aside from the relatively few scientists who study its contributions to human gut health, interest in the animal versions seems primarily limited to using its presence in the human water supply as evidence of animal waste pollution. But if these species-specific bacteria confer similar benefits to the young of other mammalian species as B. infantis confers on human infants, then dogs and cats definitely have the inside track when it comes to giving their offspring a survival advantage—if given the opportunity. This occurs because of the source of those particular bacteria. In humans, they’re among the most numerous bacteria found in the stool/feces/poop of healthy breast-fed infants.

The fact that these bacteria are beneficial rather than troublesome suggests that we may want to rethink our view of poop. For while scientists ponder this connection in humans, it’s possible that animals already may have figured out how to inoculate their young with this beneficial bacteria. Whereas most people like to put as much distance as possible between their babies and themselves and their babies’ poop, such is not the good feline and canine mom’s approach. Quite the contrary. After they finish nursing (for behavioral as well as nutritional reasons) these animal moms lick their infants’ behinds to stimulate them to defecate, i.e. poop. Then they eat the stool in the process of cleaning them up. And grooming those areas is a normal part of animal adult cleanliness too, especially for animals who recently have given birth.

Now before you give in to any knee-jerk, “Oh, gross!!” remember that it’s the lack of the human form of this bacteria in the gut and the body’s inability to produce it that contributes to severe, sometimes fatal disease in premature babies and human youngsters. And if the presence of such bacteria benefit human infants as much some research suggests, why wouldn’t it benefit animal infants and youngsters too? Sadly I could find no research that suggests veterinary scientists are even exploring this issue, but logic says that this is a strong probability.

Another aspect of normal animal nursing behavior relative to this possible bacterial recycling service is that moms taper off the rigorous cleaning when they finish weaning their young which often extends for several weeks after the young have started sampling solid food. . However, eating their own stool is a fairly common behavior in puppies and most outgrow it by a year.

This raises all kinds of fascinating questions including “Did this system evolve as a way to ensure young animals’ guts will be seeded with a microbial ecosystem that will ensure their health and survival in their particular micro- and macro-environment?” I have no answer to that, but I do find the elegance and energy-efficiency of such a system most appealing. And what might this tell us about those dogs with various digestive problems who eat their own stool? It seems reasonable that the majority do this because the stool isn’t really stool to them. Perhaps they’re doing such a poor job of digesting the food that their stool more resembles semi-digested food than waste. But what if they eat it to recycle any beneficial micro-organisms in it as well as any lost nutrients?

So many questions, so few answers! And cats add their own twists to this issue! But after reading about the components being identified in human breast milk and their benefits that may last a life-time, I recalled the popular commercial slogan that reminds us that we never outgrow our need for milk. How true that may be—if we’re talking about the species-specific breast milk and the nursing rituals that go with it that mothers of all mammalian species evolved to share with their young. Talk about a gift that keeps on giving!

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