TORONTO -- Experts are questioning existing guidelines on how to best introduce new foods to infants graduating to solids, according to a new study, which suggests those recommendations may be outdated and even potentially harmful.

Both the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC) recommend that parents introduce new single-ingredients foods one at a time and wait three to five days between each one before trying a new food to monitor for any kind of reaction.

But that practice is being called into question in a new study that surveyed 563 health practitioners -- the vast majority of whom were pediatricians -- who provide care to babies less than a year old. The survey, which focused on examining current practices by pediatric healthcare workers and was conducted in early 2019, found many of the respondents were not following AAP and CDC guidelines, and instead were recommending a shorter timeline based on clinical experience.

"There is now evidence that food diversity helps to decrease the development of allergic diseases in infants, and early peanut introduction is an important peanut allergy prevention strategy,” said lead author Waheeda Samady, a Chicago doctor and an assistant professor of Pediatrics at Northwestern University’s Feinberg School of Medicine, in a statement.

Almost two-thirds of those surveyed recommended waiting less than three days to parents. Among that group, 27 per cent recommended introducing one new food a day, while 20 per cent suggested waiting two days. Ten percent felt that introducing multiple foods in a single day was not an issue.

About 30 per cent told parents to wait three days, while just over eight per cent recommended waiting more than three days. Researchers did not find any major associations between food introduction practices and the demographics of the health practitioners.

More than two-thirds of those surveyed -- just over 69 per cent -- said they would adjust their recommendations, however, if the baby had a greater risk of developing food allergies due to a sibling or other family member with allergies, or if the infant had moderate to severe eczema.

Despite the caution around allergy risks, the National Institute of Allergy and Infectious Diseases currently recommends that infants with atopic dermatitis, or eczema, be given foods that contain peanuts between four and six months. At the same time, peanuts should only be introduced after a number of other new foods have been given first.

“If infants are required to wait three to five days between the introduction of each new food, peanut introduction may be delayed past the recommended ages,” researchers wrote in the study.

Just over 55 per cent of practitioners believed the waiting period between new foods was helpful for families, researchers found.

Even so, more than 55 per cent of those surveyed reported having seen food-related allergic reactions in less than 5 per cent of infant patients, while nearly 20 per cent reported seeing it occur in five to 10 per cent of babies.

“In practice, this recommendation may have a deleterious effect of limiting early infant food diversity, which has been reported to be associated with an increased risk of pediatric asthma and allergies,” the paper said.

“Introducing a more diverse diet in the first year of life has been shown to be associated with a reduced risk of atopic dermatitis, asthma, and food allergies up to six years of age.”

Current guidelines mean that a baby is introduced to just five to seven new food items a month, which limits their food exposure. The study noted that previous research had found that introducing certain foods later, such as potatoes, oats, rye, wheat, meat, fish, and eggs, was directly related to sensitivity to food allergens, and that earlier introductions were tied to a lower risk of allergy-related reactions like asthma and eczema.

More than half of those surveyed also felt there was a need for more training on the issue.

Close to 47 per cent of said they recommended infant cereal as the first food, but 40 per cent did not have a specific recommendation for what type of food to introduce first.

Re-evaluating current recommendations to help increase a baby’s exposure to a greater variety of foods would also support CDC’s nutritional recommendations of more food exposure in an infant’s first year to minimize “picky eater syndrome,” the paper added.

"From the perspective of food allergy detection and prevention, there is no reason why a new food can't be tried every day," said co-author Dr. Ruchi Gupta, Director of the Center of Food Allergy and Asthma Research (CFAAR) and Professor of Pediatrics at Northwestern, in a statement.

"The guidelines need to be revisited and updated to reflect the latest research on food allergy prevention and to provide greater clarity for pediatricians and parents on safe solid food introduction to infants."