The World Health Organization (WHO), the American Academy of Pediatrics and other groups recommend exclusive breastfeeding for an infant’s first six months, after which solids can be introduced.

The new data come from the Enquiring About Tolerance (EAT) study, which involved 1,303 infants and was designed to investigate whether introducing solid foods earlier might help prevent food allergies. The EAT study showed that introducing small amounts of allergenic foods to younger babies helped reduce food allergy risks. The American Academy of Pediatrics, the Australian government, and others have changed their infant feeding guidelines to reflect the findings, which were published in 2016.

Michael Perkin, of the Population Health Research Institute and St. George’s Hospital, both in London, said results from the new analysis suggest that better sleep could be another benefit of starting solids early.

As reported in JAMA Pediatrics, Perkin and his colleagues compared infant sleep and mother’s quality of life in the EAT study participants. Infants in the early introduction group began solids at about 16 weeks, on average, compared to 23 weeks in the standard introduction group.

By five months, the babies who had started eating solids earlier were sleeping longer than those whose mothers were instructed to breastfeed exclusively for six months. The difference peaked at six months of age, with the early introduction group sleeping an average of nearly 17 minutes longer, and persisted after the infants’ first birthday. Infants who started solids early also woke up about nine percent less often.

The “most clinically important” finding, Dr. Perkin said, was that parents of babies who started earlier on solid foods were significantly less likely to report that their child had a serious sleep problem.

“There was an extremely strong relationship between mother’s quality of life and infant sleep, which you anticipate,” he added. “If the baby’s sleeping poorly, the mother’s quality of life is very clearly affected.”

The findings provide some solid data to back up the long-held belief that feeding infants solid food helps them sleep better, Dr. Jae Kim, a neonatologist at of the University of California San Diego and the Radey Children’s Hospital of San Diego, told Reuters Health in a phone interview. “This is quite a well-designed study to actually answer that particular question,” he said.

“When it comes to the recommendations for mothers and their children, I think it’s still important to try to aim for exclusive breastfeeding for the first six months,” he added.

When an infant’s frequent nighttime wakeups are causing concern and anxiety, parents can consult their pediatrician about whether starting solid food would be appropriate, Dr. Kim said. But the findings don’t mean parents should feel free to give solid food to infants younger than six months to improve their sleep, he added. Early introduction of solids could cause harm in infants who aren’t developmentally ready to chew and swallow, he explained, while starting solids can also lead to earlier weaning, reducing the benefits of breastfeeding.

There’s also the question of whether longer sleep is actually a good thing for babies - although it clearly can be helpful for parents, Kim noted. Babies who sleep more may wind up consuming less breast milk, he added.

“There’s a bit of polarization around this issue,” he said. “It’s nice to have studies like this to carve out actual data to help manage this problem.”