It's recommended that children do not receive solid foods before they are 4 to 6 months old. Introducing solids earlier may increase the risk of food allergies.
A recent study found that introducing solids to babies earlier than 4 months appeared linked to a higher likelihood of developing food allergies.
In addition, breastfeeding babies for longer while they first start having foods with cow's milk protein appeared linked to a lower likelihood of food allergies.
The most common allergies among the children included in the study were egg allergies and cow's milk protein allergies.
Both of the study findings support the recommendations by pediatric and gastrointestinal doctors' organizations.
This study, led by Kate E.C. Grimshaw, PhD, RD, of the Clinical and Experimental Sciences Academic Unit at the University of Southampton Faculty of Medicine in the United Kingdom, looked at the relationship between children developing food allergies and their early diet.
The researchers compared the food diaries kept by mothers of 41 toddlers with food allergies (medically diagnosed by age 2) and 82 toddlers of the same age who didn't have food allergies.
All the children had been part of a larger long-term study started at the children's birth. In this larger study, the mothers kept a food diary of when their children first tried different foods during their entire first year of life.
Among the children who had food allergies, about half had developed symptoms of the allergies by the time they were 6 months old, and the other half had developed them after 6 months of age.
The most common food allergies found among the children were egg allergies (in 22 babies) and cow's milk protein (in 20 babies). In addition, 12 kids were allergic to more than one kind of food.
The most common symptoms of the food allergies among the children who had them were eczema (in 12 children) and vomiting (in 11 children). Diagnoses were confirmed with allergy testing.
The researchers found two main differences in the early diets of children with food allergies compared to their peers without food allergies.
Children with food allergies tended to be introduced to solid foods earlier — at 4 months old or earlier — than children without food allergies.
Across all the children, the average age for introduction of solids was 5 months, most commonly starting with rice and followed most commonly by carrots, apples, bananas and pears.
In addition, children with food allergies were less likely than those without allergies to have been receiving breastmilk when they first started eating or drinking foods with cow's milk protein, including yogurt.
Children with food allergies tended to continue breastfeeding for an average 5.5 weeks after first having cow's milk while children without food allergies continued breastfeeding for an average nine weeks after first having cow's milk.
Of all the mothers in the study, about half breastfed for more than five months, and about half breastfed for less than five months.
About half exclusively breastfed for more than two months and about half exclusively breastfed for less than two months. Rates of breastfeeding were about the same in both groups of children.
The researchers concluded that their study's findings confirmed the current recommendations of the American Academy of Pediatrics and the European Society of Pediatric Gastroenterology, Hepatology and Nutrition.
These organizations recommend not introducing solids to babies before ages 4 to 6 months.
"Our findings suggest 17 weeks is a crucial time point, with solid food introduction before this time appearing to promote allergic disease whereas solid food introduction after that time point seems to promote tolerance," the researchers wrote.
In addition, the AAP recommends that babies continue breastfeeding as solids are introduced into their diet and continue breastfeeding until at least 1 year old.
Thomas Seman, MD, a pediatrician at North Shore Pediatrics in Danvers, Mass., noted that starting solid foods can be a very stressful time in new parents' lives.
"When, how and what to feed are all questions that they ask since they know that the past influences the future," he said. "Starting food too early can cause problems – as can starting too late."
Dr. Seman said that generally children are started on solids when they are at least 4 months old and seem to require more food because they wake up hungry in the night or want more frequent feedings during the day.
"Over the last few generations, the pendulum has swung back and forth from starting cereal when the child arrives home from the hospital until waiting past 6 months before starting," he said. "Both seem to increase the risk of various food allergies."
But he added that continued breastfeeding can help with digestion and regulating the immune system.
"This, in turn, decreases allergies, as has been demonstrated by the article," he said. "Starting with cereal and slowly adding other foods, namely fruits and vegetables before higher protein foods are started, is recommended."
Dr. Seman added that any allergies that are identified mean the child should completely avoid that food for at least one year before retesting it again.
This study was published November 18 in the journal Pediatrics. The research was funded by the UK Food Standards Agency with the European Union's EuroPrevall Project.
One author sat on the scientific advisory board for Danone Baby Nutrition and another provided a lecture and consulting for Nutricia Ltd. Another author attended a board meeting for Novartis and consulted for Pepsico International and DBV Technologies on meal preparation.
The other authors reported no other potential conflicts of interest.