While the practice did not provide for totally uninterrupted nights of sleep, the study of 1,303 children in England and Wales between 2009 and 2012 showed that babies given solids earlier than now recommended did improve their sleep patterns. Half the babies were exclusively breastfed until six months of age, the other half were introduced to a variety of foods including some that are associated with allergies, including peanuts and eggs.
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.
Parents then filled in online questionnaires every month until their baby was 12 months old, and then every 3 months until they were three years old.
The EAT trial was comprised of the early introduction group, which continued to breastfeed while six allergenic foods were introduced, and the standard introduction group, which were instructed to exclusively breastfeed to around age 6 months and consumed no food in that period, according to British infant feeding guidelines.
The study showed that babies who were feed with solid food had fewer problems with sleeping and mothers had improved their quality of life.
However he also stated that he believed "the most likely explanation for our findings of improved sleep is that that these babies are less hungry".
Infants introduced to solid foods at an earlier age slept longer through the night, while infants with later introduction to solid food were more likely to have sleep problems, researchers found.
Official advice is to breastfeed exclusively for the first six months of life.
"Given that infant sleep directly affects parental quality of life, even a small improvement can have important benefits", says Dr. Michael Perkin, a co-author of the study from St George's, University of London.
The researchers' findings were limited to babies' sleep duration, not on what is nutritionally best for babies.
Responding to the study, Prof Mary Fewtrell, nutrition lead at the Royal College of Paediatrics and Child Health, pointed out that guidelines for infant feeding are now being reviewed.
However, doctors still are emphasizing the importance of continued breastfeeding, in addition to the introduction of solid food.
Despite the official piece of advice, about 75% of mothers gave solid food to their babies before five months - 26% of the babies were waking up at night frequently because of this reason.