A recent French study found that a specific species of bacteria can improve maternal behavior in stressed rat mothers. The researchers stressed the rats by putting them in the rat equivalent of a crowded subway car. (This, by the way, is stressful for both species, but at least humans have the option of calling an Uber.)
The stressed rat moms neglected their newborns. But when the scientists put Lactobacillus reuteri into their water, normal maternal behavior was restored.
The researchers found that stressed moms had higher levels of the stress hormone cortisol, which wasn’t too surprising. But they also found lower levels of oxytocin, the “cuddle hormone.”
This one-two punch affected the moms so deeply that they stopped licking their pups. For a delicate pink baby, that lack of attention is stressful. In that way, moms transfer stress to their pups.
The researchers contend that this could be a good animal model for postpartum depression (PPD). If so, it suggests a simple and cheap way to improve a devastating condition, one that doesn’t just depress mothers; PPD may have residual effects on children, too.
Lactobacillus has recently been renamed Limosilactobacillus, apparently because the original name was too easy to pronounce. We’ll shorten it to the first letter.
L. reuteri works by battling gut pathogens and generally improving gut health. That takes a load off the immune system, helping to boost oxytocin and reduce cortisol. That makes L. reuteri what’s known as a psychobiotic, acting to balance and calm the gut microbiome, easing stress and improving mood via the gut-brain axis.
Psychobiotics use the machinery of the hypothalamic-pituitary-adrenal (HPA) axis. The hypothalamus is like the brain’s tongue: It “tastes” our blood to detect hunger and stress, among other flavors.
When our gut is sour—even if you’re not aware of it—the hypothalamus can taste it. That causes it to trigger the pituitary and then the adrenal glands to produce cortisol—which is how a sour stomach can trigger anxiety.
If the stress continues, a low level of inflammation sets in. Over time, the inflammation can become systemic, involving all the organs, including the brain. If you’re a new mom, that can contribute to PPD.
The hypothalamus plays a major role in the regulation of our body weight, sociability, sleeping cycle, and stress response—all of which are compromised in depressive disorders, including postpartum depression. PPD is also associated with weight gain, which can push people toward metabolic complications, exacerbating depression and anxiety. However, the rats on L. reuteri lost weight, possibly due to the changes in oxytocin.
Could This Work on Human Mothers?
So, how relevant are these rat studies to humans? Rats and mice are fairly good proxies for psychobiotic effects, although the specific microbial species are often different. In this case, L. reuteri is known to be beneficial in humans as well. It successfully colonizes the guts of both adults and children. It balances the gut and can reduce episodes and duration of diarrhea.
An Italian study with 200 women found that L. reuteri, along with another bacteria, Bifidobacterium breve, improved mood in mothers in the first three months after birth. So, it would not be a stretch to think that L. reuteri could help with PPD.
You can find L. reuteri in probiotic blends, but you can also grow your own by consuming prebiotic fiber like galacto-oligosaccharide (GOS). L. reuteri is also found in yogurt and kefir, which might be the easiest way to consume it.
Beneficial microbes in the mother’s gut can be captured by dendritic cells, which then hitch a ride in the lymphatic system to the milk ducts. From there, this bacterial starter kit is incorporated into breast milk and passed on to the baby. That improves the baby’s mood, which makes everyone happier.
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The Bigger Picture of PPD
There are other drivers of PPD, of course. Genetics, hormonal changes, sleep deprivation, and general stress all play a part. These studies show that microbes also play a role, but whether it is a bit part or a starring turn is yet to be determined.
Nevertheless, microbes are undeniably in the script, which is wonderful, because we can improve our microbiome with diet. And when it comes to postpartum depression, any dent we can put into this miserable syndrome is worth it.
More studies are needed to pin down all the specific microbes that could further improve the moods of both mother and baby, but most of the studies so far point in the general direction of Lactobacillus and Bifidobacteria, common probiotics.
Almost everyone can benefit from yogurt or kefir. If you’re a new mom, talk to your doctor about these simple foods. Diet is a potent lever over your mental health, and where you have some control, take it.
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