Feeding infants diverse foods early may cut allergy risk, study reveals

New research reveals that feeding infants a variety of foods in their first year can help prevent allergies by strengthening gut microbiota and immune tolerance—challenging outdated advice on allergen avoidance.

Review: The Role of Diet Diversity and Diet Indices on Allergy Outcomes. Image Credit: nadiadamaris / Shutterstock

In a recent review article in the journal Frontiers in Pediatrics, researchers examined how allergy outcomes, particularly in early life, are associated with dietary diversity.

The current evidence indicates that exposure to a diverse range of foods during the first twelve months of a child’s life could lower the risk of developing food allergies, provide critical nutrients, and strengthen the gut microbiome. Early dietary exposure may help train the immune system to tolerate allergens, while skin exposure (especially in infants with eczema) may increase allergy risk. Some research also suggests that following a higher-quality diet during pregnancy could reduce asthma and wheezing in children, although there is no consistent evidence that maternal diet prevents food allergies in offspring.

Evolving Guidelines for Food Introductions

The American Academy of Pediatrics (AAP) recommended delaying allergenic foods in the guidelines they issued in the early 2000s. They suggested that milk should be introduced after the child turned one, eggs until after they were two, and fish, peanuts, and tree nuts until after they turned three. These were based on research indicating that early introductions to allergens could increase the chances of developing atopic diseases.

The American College of Allergy, Asthma, and Immunology extended delayed introduction to all infants, not just those at high risk, in 2006, but food allergy rates continued to rise across Western nations. Emerging research found that delaying the introduction of allergens could increase the risk of food allergies, especially for eggs and peanuts.

Scientists developed the dual allergen hypothesis, which suggests that early exposure to allergens orally increases tolerance, while exposure through the skin increases allergy risk, particularly for infants with eczema. The AAP revised its guidelines in 2008, noting the insufficient evidence to delay allergenic foods, but stopped short of specifying an ideal age for introduction. Guidelines now vary by country, with organizations like the National Institute of Allergy and Infectious Diseases (NIAID), the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN), and the Australasian Society of Clinical Immunology and Allergy (ASCIA) offering slightly different recommendations on timing.

Allergenic Foods and Food Allergies

An important study that looked at the impact of early introduction to peanuts was the Learning Early About Peanut Allergy (LEAP) project. Infants with egg allergy or eczema were either introduced to peanuts before their first birthday or had their caregivers told to avoid them until they turned five.

This trial found that early introduction significantly reduced peanut allergy development, while a follow-up study found that allergy risk was not increased if the children stopped eating peanuts for a year. In another ongoing study, researchers are looking at the impact of introducing infants with eczema to peanuts on the development of allergies.

Studies on the effect of introducing young children to eggs are not as conclusive. While most trials found no protective effect, one study found that introducing heated egg powder that had been boiled for 15 minutes and increasing the dosage over time significantly reduced allergy risk. The PETIT trial, in particular, found that a stepwise introduction of heated egg reduced egg allergy risk in infants with eczema. However, other studies using raw or pasteurized egg products did not find a benefit, indicating that the form and preparation of the egg may influence outcomes. A meta-analysis of this body of research, in which the one positive result may be biased, found moderately strong evidence that allergy risk could be lowered by introducing eggs when children are between four and six months old.

Regarding cow’s milk, a randomized controlled trial found that avoidance of cow’s milk formula in the first three days of life reduced sensitization, while a Finnish study found that early exposure increased the risk of allergy development. Another study in Israel found that introduction in the first two weeks of life decreased risk, while delayed introduction (between four and six months) increased it. These conflicting findings suggest that the timing of cow’s milk introduction may not have a uniform effect across different populations.

There is no conclusive evidence regarding the introduction of fish, but some studies suggest that introducing children to seafood before they are nine months old could lower their risk of asthma, rhinitis, and allergic sensitization. Fish also provides omega-3 fatty acids, which have anti-inflammatory properties, but their specific role in allergy prevention remains uncertain.

Introducing Multiple Allergens

The Enquiring About Tolerance (EAT) study examined whether introducing multiple allergenic foods early in life could reduce food allergy risk in exclusively breastfed infants. The analysis showed a significant reduction in overall food and peanut allergies in the early introduction group, but there was no significant difference after three years.

Adherence was low, especially for eggs, highlighting the challenges of early allergen introduction. Other factors, such as genetics and gut microbiota, may also influence FA development before weaning. Emerging research suggests that diet diversity may affect the gut microbiome, as a more varied diet increases fiber and nutrient intake, which in turn promotes microbial diversity. Greater gut microbial diversity has been linked to lower allergen sensitization.

Diet diversity may influence allergy prevention by affecting the gut microbiome, as a varied diet increases fiber and nutrient intake. While few studies have explored this link, research suggests that greater diet diversity is associated with increased gut microbial diversity, which may reduce allergen sensitization. Omega-3 fatty acids and prebiotics may reduce inflammation, but evidence of their role in allergy prevention is inconclusive.

Diets During Pregnancy

Diet indices such as the Healthy Eating Index, Diet Inflammatory Index, and Mediterranean Diet Index have been studied during pregnancy for their impact on allergy outcomes in offspring. Some studies have found associations between these diet patterns and improved lung function or reduced wheezing in children. However, no consistent evidence links diet during pregnancy to reduced food allergy risk.

Conclusions

Following studies like LEAP, global guidelines now recommend introducing peanut, egg, wheat, and dairy within the first year, with an earlier introduction (between four and six months) for high-risk infants. Higher dietary diversity increases nutrient intake and facilitates the development of the gut microbiome. Fiber, prebiotics, and omega-3 fatty acids may be especially important for reducing inflammation and shaping immune responses, though their direct role in allergy prevention remains uncertain. Overall, there is no strong evidence to delay the introduction of other allergens.