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Researchers say they aren’t sure why exercise increases a compound that makes breast milk healthier, or how much exercise is sufficient. Getty Images
  • Researchers say exercise can increase a compound in breast milk that may lower a child’s lifelong risk for heart disease, diabetes, and obesity.
  • Researchers say they aren’t sure why exercise enhances this compound, or how much exercise is beneficial.
  • One expert tells Healthline that exercise isn’t always an option for new mothers, and there may be other ways to improve a baby’s metabolic health.

Want to make your breast milk even more nutritious for your baby?

In a new study, researchers say moderate exercise during pregnancy increases a compound in breast milk that can lower a child’s lifelong risks for heart disease, diabetes, obesity, and other conditions.

Recent research on animals has shown that mothers who exercise before and during pregnancy pass on protections against impaired glucose metabolism, decreased cardiovascular function, and obesity.

However, the medical community still isn’t sure what exact compound delivers the benefits, or how exercise may affect it.

Kristin Stanford, PhD, an associate professor of physiology and cell biology at The Ohio State University, says researchers believe oligosaccharide 3′-sialyllactose (known as 3’-SL or 3’SL), a compound in breast milk, is what protects infants.

Along with other milk oligosaccharides, 3’SL is likely only synthesized in the mammary gland and only during lactation, Stanford told Healthline.

“We are not sure how exercise increases 3’SL,” she added.

Stanford’s study, published in Nature Metabolism, highlights research on mice and humans.

Stanford’s team looked at mice born to sedentary mothers. Researchers then fed them milk from female mice who were active during their pregnancies. They followed the mice for a year after their nursing period.

“Just supplementing 3’SL during the nursing period improved glucose metabolism, reduced fat mass, and reduced body weight in male offspring, and preserved cardiac function in female offspring,” Stanford said.

Additionally, researchers observed that the mice who were fed 3’SL during their nursing period and put on a high fat diet were protected from the detrimental effects of a high fat diet.

In humans, the team examined about 150 pregnant and postpartum women who wore activity trackers.

They discovered that women with more steps per day had higher amounts of 3’SL.

“We measured 3’SL in milk 2 months after birth and it was still correlated to steps per day and activity during pregnancy,” Stanford said.

Higher levels of 3’SL weren’t necessarily related to exercise intensity, so even moderate exercise, like a daily walk, is enough to reap the benefits, Stanford adds.

Researchers aren’t sure whether exercising after birth can keep 3’SL levels up, or how much exercise is needed to keep levels high enough to benefit infants.

Stanford says isolating 3’SL could be useful as it can be added to infant formulas to provide the “significant impacts on offspring health” found in breast milk.

“In women, 3’SL is correlated with activity and steps per day, and that in a mouse, 3’SL improves metabolic health and cardiac function in offspring,” Stanford said. “More work needs to be done to fully determine the role of 3’SL consumption in human infants.”

In the future, she hopes to pinpoint the mechanism through which 3’SL improves metabolic health and cardiac function in offspring, as well as determine how exercise increases 3’SL in milk.

Though the research seems promising, Yaffi Lvova, a registered dietitian nutritionist from Arizona specializing in helping mothers and infants, is concerned about the stress level it could place on new moms.

“There is a lot of pressure during new motherhood and very little support. Adding exercise to the to-do list without first effectively evaluating the mental and physical state of the mother is dangerous, having both psychological and physical consequences,” she told Healthline.

Exercise has been shown to improve symptoms of depression and anxiety. New mothers are prone to those conditions, but that doesn’t mean every new mother should exercise, Lvova says.

“She may overextend herself while in a state of extreme fatigue in order to provide the best for her infant, whether or not she is putting herself at risk by doing so. That is the nature of motherhood,” Lvova said.

“This study does not address the idea of overexercising, or the possible ill effects that a baby-mother dyad may experience from the mother overtaxing herself either physically or psychologically,” she added.

While there are documented benefits of 3’SL on the microbiome and mental health, women who aren’t in a place to exercise have other opportunities to support their infant’s microbiome, Lvova says.

She would like to see more factors in future research as it pertains to exercise and breast milk nutrition, such as the state of the mother’s nutrition, sleep quality, and mental state.

“When we advise a new mom to include exercise without also considering these other biological and psychological factors, we run the risk of adding to the already stressful mental and physical load of the new mother,” Lvova said.