It wasn’t until the six-month mark in my first pregnancy that I really started to exercise. I know that sounds strange, but for the first two trimesters severe nausea made it hard for me to do anything more vigorous than brisk walking. When the morning sickness finally lifted, I felt euphoric — pedaling along Atlanta’s winding bike path at top speed, jogging with my husband, hiking in the North Georgia Mountains.
But I also worried. The advice books I read always included cautious reminders not to overdo it, to talk to your doctor, to be careful not to get your heart rate up too high. This was in 1999, before anyone was sharing stories about pregnant women doing ballet in the third trimester, marathon-running pregnant mamas, or pregnant power lifters.
My doctor’s attitude was not overtly in favor of exercising. Having recently given birth to her second child, the obstetrician’s only advice for me was “be careful.”
This attitude was likely based on her own bias, as well as on a lack of research specifically about exercise during pregnancy. Though common sense would dictate that exercise during pregnancy could only be a good thing (right?), and though we’ve long known that an active lifestyle has myriad benefits — including improving mood, memory, and erectile function, lowering the risk of death from heart disease, helping reverse adult onset diabetes, and increasing muscle strength — it is notoriously difficult to do high-quality studies on pregnant women.
But now a growing body of research — mostly done on rodents — is revealing just how beneficial it is for the offspring when their mothers exercise during pregnancy. In 2014 researchers at Dartmouth College revealed that exercise during pregnancy enhances brain function in offspring, and that this boost to the brain continues into adulthood. In 2015 a team at the Washington University School of Medicine found that exercise in pregnancy lowers the risk of heart defects in offspring.
A new scientific study from the University of Colorado Boulder, published in the journal Immunology and Cell Biology on January 12, 2016, presents more interesting findings about the benefits of exercise. The human body is teeming with microorganisms — many of which are thought to play an essential role in immune function, metabolism, and digestion. Exercise, it turns out, has a pronounced positive effect on these microbial communities, especially when done early in life.
Examining the fecal matter of genetically identical laboratory rats who were given access to exercise versus rats who had no way to exercise, researchers found that young rats that ran on wheels every day had much more beneficial bacteria in their guts than rats who did not. The beneficial bacteria found most abundantly in the intestines of the young rats who exercised have been associated with lean muscle and reduced stress.
“Adult animals and young animals both reap these benefits, but a young animal reaps these benefits in a more permanent fashion,” Monika Fleshner, a professor in the Department of Integrative Physiology at the University of Colorado Boulder and one of the authors of the study, explains when I reach her by phone at her laboratory.
Wait, what? The bacteria in our guts influence our health?
“These are crazy ideas, right?” Fleshner laughs, backtracking to explain that scientists have discovered that the bacteria that reside in the intestines of humans and other mammals, “participate in real and meaningful ways in the development of our immune system and our brains, as well as the regulation of our metabolism and the way our bodies respond to stress.”
Though Fleshner and her team did not study pregnant rats in these experiments, Fleshner says that the microbes babies are populated with very early in life play an important role in their health and well-being. “We are populated within the first moments of birth from bacteria from our mothers,” Fleshner says. “Those bacteria go on to live in a symbiotic relationship on our skin, in our mouth, as well as in our intestines. The type of bacteria are very important for our normal, healthy development.”
Fleshner has been studying the effects of exercise for twenty years. She says the take-away message from these new experiments is that parents should encourage their children to exercise at very young ages because the benefits to their microbes will be life long.
She also encourages pregnant women — and everyone else — to be active.
“You can reap a lot of mental health benefits long before you see big physical changes,” Fleshner tells me. “A little bit of exercise, just getting out every day, will help you improve your mood, have more energy, and sleep better. You don’t have to become an athlete to get a lot of the health benefits.”
Sixteen years ago when I was flying down the bike paths of Atlanta, I thought I was just soaking up the sunshine and celebrating the end of so many months feeling nauseous. Who knew I may have also been setting the stage for my baby’s microbiome?