Researchers studied over 20,000 families across five Chinese cities to understand what causes food allergies in children. They looked at three main factors: vitamins and supplements the mother took during pregnancy and the child ate, things in the home environment like flooring and toys, and outdoor air pollution. The study found that certain vitamins and supplements appeared to protect children from food allergies, while some household items and air pollution increased the risk. Interestingly, good nutrition seemed to help reduce the harmful effects of pollution and household factors on food allergy development.

The Quick Take

  • What they studied: How vitamins, supplements, things in your home, and air pollution together affect whether children develop food allergies
  • Who participated: Over 20,700 families with children from five different cities in China, surveyed about their health, nutrition, and home environment
  • Key finding: Children whose mothers took certain vitamins during pregnancy and who ate iron, vitamins, and fish oil had fewer food allergies. However, vitamin D supplements and some household items like plastic toys and air conditioning were linked to more allergies. Air pollution, especially nitrogen dioxide, also increased allergy risk.
  • What it means for you: This suggests that good nutrition during pregnancy and childhood may help protect against food allergies, but more research is needed before making major changes. Talk to your doctor before starting new supplements, as this study shows vitamin D supplements may increase allergy risk in some cases.

The Research Details

Researchers collected information from families in five Chinese cities using questionnaires about what mothers ate during pregnancy, what children ate, their home environment, and whether children had food allergies. They used statistical methods to look for patterns and connections between these factors and food allergies. The study examined how these different factors might work together—for example, whether good nutrition could reduce the harmful effects of air pollution on allergies.

Food allergies in children are becoming more common, and scientists don’t fully understand why. This study is important because it looks at multiple factors at the same time—not just nutrition or just pollution, but how they interact. Understanding these connections helps doctors and parents know what might increase or decrease allergy risk.

This was a large study with over 20,000 families, which is a strength. However, it was a survey-based study where families reported their own information, which can sometimes be less accurate than direct measurement. The researchers tested many different factors, which increases the chance of finding false connections by accident. The authors themselves warn that some findings may not be real and need to be confirmed by other studies. The study was done in China, so results may not apply equally to other countries with different environments and diets.

What the Results Show

Children had fewer food allergies when their mothers took iron, vitamins A through E, cod-liver oil, DHA (a fish oil), protein powder, or probiotics during pregnancy. Similarly, when children themselves ate these same supplements and vitamins, their allergy risk went down. The protective effect was strongest for iron, vitamins A, B, C, and E, and fish oil. In contrast, when children took vitamin D supplements or probiotics, their food allergy risk actually went up, which was surprising and unexpected. The study suggests that the timing and type of supplement matter—what helps during pregnancy may not help the same way in childhood.

The home environment also played a role. Homes with ceramic tile, stone, or cement floors had fewer allergies compared to other flooring types. Using glass baby bottles and plastic toys was linked to more allergies, while silicone rubber bottles and air filters reduced allergy risk. Using air conditioning in summer and having mosquitos in the home were associated with higher allergy rates. These findings suggest that both what children touch and breathe at home matters for allergy development.

Previous research has suggested that vitamins and a clean environment might protect against allergies, and this study supports that idea. However, the finding that vitamin D supplements increase allergy risk contradicts some earlier research, suggesting the relationship is more complex than previously thought. The connection between air pollution and allergies has been shown before, but this study adds detail by showing that good nutrition may help reduce pollution’s harmful effects.

The study relied on families remembering and reporting what they ate and their home conditions, which can be inaccurate. Because researchers tested so many different factors (vitamins, household items, pollutants), some findings may have occurred by chance rather than being real effects. The study was done in China, so the results may not apply to children in other countries with different diets, climates, and pollution levels. The study shows associations (things that happen together) but cannot prove that one thing causes another. Finally, the researchers themselves noted that some findings may be false positives and need to be confirmed by future studies.

The Bottom Line

Based on this research, pregnant women and children may benefit from adequate iron and vitamins A, B, C, and E, though you should talk to your doctor about appropriate amounts. The finding about vitamin D is concerning and suggests caution with vitamin D supplements—discuss with your pediatrician before starting them. Maintaining a clean home environment with good air quality appears helpful. However, these recommendations are preliminary and should not replace advice from your healthcare provider. (Confidence level: Moderate—more research is needed to confirm these findings.)

Pregnant women and parents of young children should find this interesting, especially if they have a family history of allergies. People living in areas with air pollution may want to pay extra attention to nutrition and home environment. However, these findings are most directly applicable to families in similar environments to the study locations. Anyone considering supplements should discuss with their doctor rather than self-treating based on this study.

If these findings are real, protective effects of good nutrition would likely develop gradually during pregnancy and early childhood, not overnight. You wouldn’t expect to see changes in allergy risk in days or weeks, but rather over months to years of consistent nutrition and environmental improvements.

Want to Apply This Research?

  • Track maternal vitamin intake during pregnancy and child’s daily supplement use (iron, vitamins A/B/C/E, fish oil) alongside any food allergy symptoms or reactions. Record dates and types of supplements taken to identify patterns.
  • Users can set reminders to take recommended vitamins consistently during pregnancy and early childhood, log home environment factors (flooring type, air filter use, toy materials), and monitor outdoor air quality on high-pollution days to adjust outdoor activities accordingly.
  • Create a long-term log tracking supplement adherence, home environment changes, air quality exposure, and any new food allergy symptoms. Review monthly to identify correlations between nutrition, environment, and allergy development. Share data with healthcare provider for personalized guidance.

This research suggests associations between nutrition, environment, and food allergies but does not prove cause-and-effect relationships. The study was conducted in China and may not apply equally to other populations. Before making changes to your diet, supplements, or home environment based on this research, consult with your healthcare provider or pediatrician. Do not start or stop any supplements without medical guidance. This information is for educational purposes and should not replace professional medical advice. Some findings may not be confirmed by future research, as the authors themselves noted.