Exercise Might Make Breast Milk's Goodness Even Better
Exercise is part of a healthy lifestyle, but a new study suggests it also increases the amount of a beneficial compound called 3SL in the breast milk of both humans and mice.
Based on that, researchers think that its benefits to babies could last for decades, potentially making them less likely to experience such chronic illnesses as obesity, type 2 diabetes and heart disease as they age.
"As long as they were given 3SL during their nursing period, they were protected as they aged," said Kristin Stanford, who led the mouse portion of the study at Ohio State University's Wexner Medical Center. "In the absence of any self-intervention, this has absolutely provided a really strong protective effect."
Though past studies have shown the benefit of maternal exercise to offspring, this study begins to answer the question of why, Stanford said.
The human side of the research was led by Aline Andres at Arkansas Children's Nutrition Center and included 150 pregnant and postpartum women who used activity trackers to count their steps. The women then provided samples of breast milk, which researchers analyzed.
Mothers whose trackers had recorded even a moderate number of steps showed a greater amount of 3SL in their breast milk, without considering exercise intensity. And more steps showed even greater levels of 3SL in the women.
Andrea Berardi was one of those women. The Ohio resident has always enjoyed exercise, running marathons and doing deep-stretch yoga classes, so continuing to stay active during pregnancy came naturally. Now the mom of a 6-month-old daughter, she joined the study right after her daughter was born.
Though Berardi initially thought she would breastfeed her daughter for six months, her goal now is one year. To think that what she's doing now could enhance her daughter's health for years to come is amazing, she said.
"So many people want to give their children the best step forward and do everything that's best for them," Berardi said. "Anything to help her bypass those major issues in her medical charts, that's obviously a goal of mine."
Stanford was thrilled to see the human findings mirrored what her team saw in mice.
"It was really exciting for us to have them do the study in a totally different institution and see the same thing that we had seen in mice that they were seeing in humans," said Stanford, who is an associate professor of physiology and cell biology at Ohio State's Dorothy M. Davis Heart and Lung Research Institute.
The research was published June 29 in the journal Nature Metabolism and also included scientists from the University of California, San Diego, and the Joslin Diabetes Center in Boston.
In mice, researchers found the offspring of those who exercised had reduced fat mass or body weight, as well as improved glucose metabolism, Stanford said. When other mouse pups were given the breast milk of the exercise-trained mice, they showed these same benefits.
"This showed that the milk is definitely an important factor in that," Stanford said. "It was really enough to contribute to these overall metabolic effects."
Even when the mouse pups were fed a high-fat diet later, they still had improved metabolism, cardiac function and body composition. The increased 3SL in breast milk for moms who were more active held true, even if the moms were overweight.
"It didn't really matter what your starting BMI [body mass index] was or your starting body weight, as long as you were moving, we saw these effects," Stanford said.
"If something as simple as increasing your steps per day while you're pregnant can protect your child from some of these things or even have a minimal effect on how they develop in a positive way, I think that the implications for public health can be pretty dramatic," Stanford added. But the study could not prove that exercise actually caused 3SL levels to rise.
Researchers also are examining whether they can isolate 3SL for potential future inclusion in infant formula or infant supplements.
Breast milk is remarkable, said Connie Diekman, a food nutrition consultant in St. Louis.
"The validation of this study is what we have long said, that breast is best," Diekman said. "It is that foundation that it lays for the rest of life that is so vitally important and that we don't fully understand.
"It appears even if a mom can do it for six weeks or two months, that infant gets a very significant benefit for the rest of their lives," she added.
For mothers who may not be able to breastfeed or who choose not to, "you still can provide your infant a well-balanced, healthful eating plan," Diekman said.
There's more on breastfeeding at the American Academy of Pediatrics.
SOURCES: Kristin Stanford, Ph.D., associate professor, physiology and cell biology, Ohio State University, Dorothy M. Davis Heart and Lung Research Institute, Columbus; Connie Diekman, R.D., food nutrition consultant, St. Louis; Andrea Berardi, Ohio; Nature Metabolism, June 29, 2020