Food Introduction in Infancy

Despite an abundance of information available regarding pediatric food introduction, significant discrepancies exist in providers’ guidance to parents on the optimal timing, types, and methods of introducing solid foods to infants. Addressing this education gap is essential for ensuring healthy introduction of complementary foods, mitigating the rising incidence of food allergies, and preventing feeding challenges in infants overall.After completing this article, readers should be able to: Appropriately guide parents of atopic/nonatopic infants on the introduction of allergenic foodsDescribe the risk and benefits of early introductionProvide guidance to parents regarding introduction of complementary foodsList the protective benefits of breastfeeding for food allergy developmentThe introduction of solid foods to infants marks a significant milestone in their development, yet introducing solid foods can also be a source of confusion and concern for parents and caregivers. With overwhelming information available, navigating the infant feeding landscape can be intimidating. In recent years, a growing body of research has shed light on optimal practices for introducing solid foods to infants. This research offers invaluable insights for parents seeking to provide the best nutrition for their children. Nevertheless, increased awareness about food allergies has also led to increased anxiety among parents regarding the introduction of new foods to their infants. Close to 6% of children in the United States have food allergies,1 which has an annual cost of $24.8 billion.2 The most prevalent food allergies in children include peanut, egg, and cow’s milk.2 This review article consolidates recommendations by presenting the current evidence surrounding infant food introduction. Key topics addressed include the optimal timing and methods for introducing solid foods, strategies for safely introducing potentially allergenic foods, and special considerations for children with atopic conditions such as atopic dermatitis and food allergies. This review seeks to provide health care professionals and caregivers the knowledge to make informed decisions on food introduction and mitigate the risk of adverse reactions in infants and children.Complementary feeding refers to introducing foods alongside human breast milk or commercial formula to meet the nutritional needs of infants as they grow beyond age 6 months.3 This transition from exclusive milk feeding to a diverse diet is crucial for the infant’s optimal growth and social, emotional, and cognitive development.3 In this section, we will discuss the timing, selection of foods, preparation methods, progression of the diet, and possible risks of complementary food introduction based on current data and recommendations.The timing of introducing complementary foods is a critical factor in infant nutrition.4,5 Exclusive breastfeeding through the first 6 months of life has been recommended by the World Health Organization (WHO) since 2002.3,4 The American Academy of Pediatrics (AAP),3 American College of Obstetrics and Gynecology (ACOG), and the American Academy of Family Physicians (AAFP) all also recommend initiating complementary foods around age 6 months, while avoiding introduction before 4 months.4 The AAP also advocates that breastfeeding can be continued beyond age 2 years if desired by both the mother and infant.3 Delaying the introduction of complementary foods beyond 6 months may lead to nutritional deficiencies5,6; although currently controversial, there is a chance that introducing solids too early may increase the risk of obesity.4–6Organizations such as the US Department of Agriculture and the WHO recommend incorporating foods rich in macronutrients such as protein, fats, and carbohydrates and micronutrients such as iron, zinc, calcium, and vitamins A, B, C, and D while discouraging the inclusion of caffeine, added sugars, and high-sodium foods.3,5,7Common first foods include the following: Iron-rich foods: Experts recommend that infants receive a daily intake of iron-rich foods in the form of iron-fortified cereals, red meat, fish, poultry, legumes, and nuts.5–7Pureed fruits and vegetables: The addition of pureed or mashed fruits and cooked vegetables such as bananas, leafy greens, squash, potatoes, carrots, and peas are excellent sources of vitamin A, vitamin C, B vitamins, and calcium.7Protein-rich foods: Cooked and pureed meats, poultry, fish, eggs, grains, nuts, and legumes provide essential protein, iron, and zinc.7Because iron stores become depleted by age 4 to 6 months, iron-fortified cereals and pureed meats are important complementary foods to first introduce to breastfed infants.8 Despite the common practice of pediatricians recommending the introduction of iron-fortified cereals and vegetables before fruits to avoid exposure to sweeter flavors, there is no evidence to support any particular order of solid food introduction.8 The WHO suggests gradually introducing various food textures and consistencies, beginning with pureed and mashed foods before advancing to more solid options, aiming for children to partake in family meals by approximately age 1 year.6 Additionally, it is recommended to introduce foods with lumpy textures, such as finger foods, between ages 8 and 10 months, because delaying beyond this timeframe has been linked to pickiness and food refusal behaviors.6,7 When introducing solids, caution must be taken with foods that can be choking hazards, such as raw fruits and vegetables (grapes and carrots) and nuts.7 Parents should emphasize caution in ensuring that the consistency of the food is adequate for the child, such as using purees or cutting food into smaller pieces.7 Furthermore, the child should have adequate head control to sit in a feeding chair and be eager to consume foods.The early introduction of solids has been associated with potential risks and benefits, particularly concerning allergies, obesity, and the intestinal microbiome.4,9Allergies: Although early introduction was once thought to increase allergy risk, recent evidence suggests early introduction may decrease the likelihood of developing food allergies.4 Two studies, Learning Early About Peanut Allergy (LEAP) and Enquiring About Tolerance (EAT), demonstrate lower allergy rates in infants exposed to allergenic foods before age 6 months, highlighting a potential opportunity to achieve oral tolerance with early introduction.4Obesity: The evidence is limited that introducing solids before age 6 months increases the risk of obesity.4 Although most studies found no association between early introduction and future obesity, some observational studies hint at a potential link, although this could be influenced by factors such as rapid weight gain rather than early solid introduction.4,9Intestinal microbiome: The introduction of solids alters the infant’s intestinal microbiome, increasing diversity and shifting bacterial populations.4 Some association has been found tying low intestinal microbial diversity during infancy to a risk for developing conditions such as colic, eczema, asthma, and type 1 diabetes in the future.4The Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA) and the Food Allergy Safety, Treatment, Education, and Research (FASTER) Act, pivotal in the field of food allergies, have identified major food allergens. FALCPA, for instance, recognized peanuts, cow’s milk, egg, wheat, soy, tree nuts, fish, and crustacean shellfish as the common food groups that make up most food allergies (Table 1).10 The FASTER Act, on the other hand, identified sesame as a major food allergen in the United States, with labeling requirements taking effect on January 1, 2023.10 It is worth noting that egg and cow’s milk are the most common allergens in infancy.11According to the 2013 American Academy of Allergy, Asthma, and Immunology (AAAAI), Canadian Society of Allergy and Clinical Immunology (CSACI), and the 2019 AAP Clinical Report, if a child is diagnosed with a food allergy and is exclusively breastfeeding, the mother does not have to exclude these foods from her diet.12 Another study showed that breastfeeding infants had a lower risk of developing wheat allergy if introduction occurred while they were still being breastfed.12 A study in Canada showed that if peanuts were introduced to breastfeeding infants via breastmilk from a peanut-consuming breastfeeding mother and then having direct oral ingestion of peanuts prior to age 1 year, such introduction was protective against peanut sensitization until at least age 7 years.13 The AAAAI, American College of Allergy, Asthma, and Immunology (ACAAI), and CSACI also wrote a consensus report that some research indicates that concurrent breastfeeding and allergen introduction can potentially protect against the onset of food allergies.12 However, there are still some conflicting data on this benefit, and the duration of breastfeeding as a contributing factor remains unresolved.12 The WHO conducted a systemic review, comparing exclusive breastfeeding until age 6 months vs 3 to 4 months.14 The benefits of exclusive breastfeeding were lowering the risk of gastrointestinal illnesses in children and quicker weight loss for mothers. However, there are no data suggesting that it will reduce the risk of allergies.14Based on studies showing benefits, there has been a switch in the recommendations for the early introduction of allergenic foods. The United Kingdom–based trial mentioned earlier, LEAP, showed that introducing peanuts prior to age 1 year decreases the likelihood of developing a food allergy to peanuts in high-risk infants.15 An Australian study, EarlyNuts, showed that the rate of early introduction of peanuts increased from 28.4% to 88.6% after an update to the infant feeding guidelines in 2016 following the LEAP study.16The National Institute of Allergy and Infectious Diseases-Addendum Guidelines (NIAID-AG) recommend consuming safe peanut powders/flours and snacks such as peanut puffs (Bamba or Cheeky Monkey) on an average of 2 g of peanut protein (∼2 teaspoons) 3 times a week to maintain tolerance.12 The peanut protein powder can be mixed into breast milk or formula, or with pureed foods.12 The Prevention of Egg Allergy with Tiny Amount Intake Trial (PETIT) in Japan showed a protective effect when infants consumed 50 to 250 mg of cooked egg daily between ages 6 and 12 months.12 Fully cooked/baked eggs (ie, muffins) are heated to at least 350 °F for at least 30 minutes.17 The recommendation is that fully cooked/baked eggs should be introduced first, compared with raw or undercooked eggs, as nonbaked eggs have a higher likelihood of triggering an allergic reaction.12 Sesame and tree nuts can be introduced in pureed or paste-type foods to avoid choking hazards, also around age 6 months, once the infant has tolerated typical complementary food introduction.12 The overall goal is regular exposure to allergenic foods throughout the years to maintain tolerance, as there is no good consensus regarding the specific protein amount or interval of ingestion.12The recommended age for introduction of specific complementary allergenic foods is varied. Soriano et al reviewed the available evidence and found that peanut and egg introduction should occur between ages 4 and 11 months to lessen the likelihood of developing a food allergy.9 Scarpone et al found evidence showing that introduction at age 3 to 6 months had a 40% reduction of egg allergy development, whereas introduction at age 3 to 10 months had a 69% reduction of peanut allergy.18 Roberts and colleagues developed a model for the burden of peanut allergy across an entire population using data from the LEAP, EAT, and other pivotal trials.19 The model revealed that a 77% reduction in the burden of peanut allergy can be achieved if peanut is introduced to high-risk infants with any eczema severity at age 4 months and in all other infants at age 6 months.19The evidence for when to introduce cow’s milk into the diet for allergy prevention shows low certainty,9,18 but whole liquid cow’s milk should be delayed until age 1 year due to adverse health effects, particularly iron deficiency anemia.5 Other forms of cow’s milk, such as yogurt, cheese, custards, and commercial formula, can be introduced before age 1 year.20 Hydrolyzed formula is not recommended as a means for food allergy prevention.12 The evidence shows low certainty regarding the timing of the introduction of wheat/gluten into the diet and its relationship with wheat allergy.9,18 However, there is some high-certainty evidence showing that early introduction did not have an increased risk for developing celiac disease.9The first introduction of a food should be performed at home vs a clinical environment, but it is acceptable to introduce under clinical supervision if there is a risk that, due to parental fear, there will be unnecessary avoidance of the food.12 It has been common to recommend introducing 1 complementary new food every 3 days to see if reaction occurs, although data do not support this method.12 Acidic fruits commonly cause a contact irritation reaction that can be mistaken for an immunoglobulin E (IgE)–mediated reaction, which can cause further delayed introduction of the food.12 However, contact dermatitis does not carry the risk of progression to anaphylaxis and is often self-limited, so delayed introduction for this reason is not recommended.12 Nonallergenic complementary foods should be introduced first to assess tolerance of solid foods and to prevent intolerance from being mistaken for an allergic reaction.12The topic of introducing foods, particularly those that are potentially allergenic, to patients with existing atopic conditions has been evolving. Since the publication of the LEAP trial in 2015,15 many of the guidelines published by professional societies around the world have focused on guiding parents and practitioners on introducing peanuts. As mentioned above, most of these guidelines need to be supported by sufficient evidence regarding the timing of introducing other significant allergens. Also, these guidelines vary in how they define infants at higher risk and whom and when to test before food introduction. In response, the AAAAI, ACAAI, and CSACI provided an extensive review of evidence and formulated a consensus statement in 2020 to address how to define an infant as high risk for the development of food allergy, the timing of introduction of potentially allergenic foods to these patients, and when to refer to an allergist for possible testing or supervised oral food challenge.12There is no international consensus on defining a high-risk infant for developing food allergy. The LEAP and EAT studies set the current standard for high-risk patients: severe eczema and sensitization to egg allergy or other food.21 The NIAID-AG include mild to moderate eczema as a high-risk factor, and previous guidelines include having a first-degree relative with atopy as a risk factor; however, some considered this too inclusive.12 To help clinical decision-making, a 2021 AAAAI/ACAAI/CSACI consensus report proposed a risk gradient for the development of food allergy to help clinicians risk-strategize their patients.12 The infants at highest risk are those with severe eczema, followed by those with other food allergies, followed by those with mild to moderate eczema, followed by those with a family history of atopy.12 Therefore, for the purpose of this article, we are defining high-risk infants as those with eczema, asthma, other food allergies, and a family history of atopic diseases.The AAAAI/ACAAI/CSACI workgroup reviewed 7 randomized control trials that investigated the relationship between the timing of the introduction of peanuts and eggs and the development or prevention of food allergy in both standard-risk and high-risk patients.12 They concluded that peanut and egg allergens should both be introduced between ages 4 and 6 months for all infants.12 There are less data surrounding the timing of introducing other food allergens and the impact on the development of food allergies; however, current observational studies suggest there is no harm in early introduction of these allergens other than the potential harm in delaying introduction.12 It is important to emphasize to patients that regular, continued consumption of the food is essential to maintaining tolerance once the food is introduced.12The guidelines for allergy testing prior to food introduction have been continually evolving. After the LEAP study 2015, the recommendation was to test before introducing peanuts to those infants they defined as high-risk.22 The British Society of Allergy and Clinical Immunology 2018 recommended peanut introduction at age 4 months without risk stratification or testing for all infants.23 After a review of the evidence, the AAAAI/ACAAI/CSACI consensus statement in 2021 concludes that for both standard and high-risk infants, skin or serum IgE testing is not required prior to the early introduction of peanut or egg.12 However, screening should remain an option for families who want to test before the introduction rather than delaying the introduction, which could cause more harm.12 Overall, the current stance is that there is no evidence to support preemptive allergy testing prior to introduction of allergenic foods due to the risk of getting false positives, the low-cost-effectiveness, and the low risk of a severe reaction on first exposure.24SummaryExclusive breastfeeding is recommended through the first 6 months of life (WHO, ACOG, AAP, and AAFP),3,4 and the AAP advocates that breastfeeding can be continued beyond age 2 years if both the mother and infant desire.3 (Level A; Strong Recommendation, based on clinical studies)Complementary foods should be rich in macronutrients such as protein, fats, and carbohydrates and micronutrients such as iron, zinc, calcium, and vitamins A, B, C, and D.3,5,7 These foods should be absent of or have minimal amounts of caffeine, added sugars, and high-sodium content.3,5,7 (Level A; Strong Recommendation, based on clinical studies)The LEAP study showed that introducing peanuts before age 1 year decreases the likelihood of developing a food allergy to peanuts in high-risk infants.13 (Level A, Strong Recommendation, based on clinical studies)The PETIT study showed a protective effect when infants consumed cooked eggs daily between the ages of 6 and 12 months.12 (Level A, Strong Recommendation, based on clinical studies)There is evidence that liquid cow’s milk should not be introduced until after age 1 year for the risk of iron deficiency anemia, but families may introduce nonliquid cow’s milk prior to this age.5,9,18,20 (Level A, Strong Recommendation, based on clinical studies)The evidence shows low certainty on the timing of the introduction of wheat/gluten into the diet and its relationship with wheat allergy.9,18 (Level C, based on observational studies and inconsistent study findings)An AAAAI/ACAAI/CSACI consensus report proposed that severe eczema is the highest risk factor for an infant developing a food allergy.12 (Level B, based on clinical and observational studies)There is no evidence to support preemptive allergy testing prior to introducing allergenic foods due to the risk of getting false positives, the low-cost-effectiveness, and the low risk of a severe reaction on first exposure.24 (Level C, based on observational studies and inconsistent study findings)The overall goal is regular and maintained exposure to allergenic foods throughout the years to maintain tolerance.1 (Level C, based on observational studies and inconsistent study findings)

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