Researchers in Shanghai followed over 1,000 babies from birth to age 2 to understand how vitamin D levels at birth and certain genes affect the risk of developing food allergies. They found that babies with low vitamin D at birth were more likely to develop food allergies early on, especially if they had certain genetic variations. Interestingly, the relationship wasn’t straightforward—both very low and very high vitamin D levels seemed problematic. The study suggests that vitamin D’s effect on allergy risk depends on a baby’s genes, meaning different babies might need different vitamin D levels during pregnancy to prevent allergies.

The Quick Take

  • What they studied: Whether vitamin D levels in newborn babies’ blood and specific genes related to immune function work together to influence the chances of developing food allergies in early childhood.
  • Who participated: 1,049 mother-baby pairs from Shanghai, China. Researchers measured vitamin D in the baby’s umbilical cord blood at birth and tracked whether the babies developed food allergies at 6, 12, and 24 months old.
  • Key finding: Babies born with low vitamin D had 2.5 times higher risk of food allergies at 6 months. However, the effect was complicated by genes—babies with certain genetic variations had up to 26 times higher allergy risk when vitamin D was low, while high vitamin D sometimes reduced the protective benefit of other genes.
  • What it means for you: If you’re pregnant, vitamin D levels may matter for your baby’s allergy risk, but the ‘right’ amount might depend on your family’s genes. This suggests a one-size-fits-all vitamin D recommendation may not work for everyone. Talk to your doctor about your individual situation, especially if you or family members have food allergies.

The Research Details

This was a prospective cohort study, which means researchers followed the same group of babies over time from birth to age 2. They measured vitamin D levels in cord blood (blood from the umbilical cord at birth) and identified five specific genetic variations in genes related to immune system function. The researchers then tracked which babies developed food allergies and looked for patterns between vitamin D levels, genetic variations, and allergy development.

The study used standardized medical criteria to diagnose food allergies at three time points: 6 months, 12 months, and 24 months of age. Researchers also collected information about birth season, whether the mother had allergies, and other environmental factors that might influence allergy risk. They used statistical methods to determine whether vitamin D and genes worked together to increase or decrease allergy risk.

This research approach is important because it allows scientists to see how factors present at birth (vitamin D and genes) influence health outcomes as children grow. By following babies over time rather than just looking at one point in time, researchers can establish that vitamin D and genes came before the allergies developed, not the other way around. The study also examined how vitamin D and genes interact—meaning they don’t work independently but rather influence each other’s effects.

The study included a large number of participants (over 1,000 mother-baby pairs), which makes the findings more reliable. The researchers used objective genetic testing methods and standardized allergy diagnosis criteria. However, the study was conducted in one city in China, so results may not apply equally to all populations worldwide. The study measured vitamin D at one point in time (birth), so it doesn’t show how vitamin D changes during pregnancy or infancy affect allergy risk.

What the Results Show

The research revealed a U-shaped relationship between vitamin D and food allergy risk, meaning both very low and very high levels appeared problematic. Babies with vitamin D levels below 20 ng/mL (deficient) had 2.55 times higher risk of food allergies at 6 months compared to babies with adequate levels. Babies with levels above 25 ng/mL (high) also had increased risk, though slightly less dramatic at 2.38 times higher.

The most striking finding involved the interaction between genes and vitamin D. Babies with certain genetic variations in immune-related genes had dramatically increased allergy risk when vitamin D was low. For example, babies with a specific variation in the IL4R gene had 26 times higher allergy risk when vitamin D was deficient. Similarly, babies with certain variations in the IL13 and IL-4 genes had 6.5 and 4 times higher risk, respectively, under vitamin D deficiency.

Interestingly, by age 2, the protective effect of low vitamin D deficiency weakened, suggesting that vitamin D’s influence on food allergy risk may be strongest in the first 6 months of life. Additionally, a genetic variation in the MS4A2 gene that normally appeared protective lost some of its benefit when vitamin D levels were very high, suggesting that too much vitamin D might interfere with this gene’s protective effect.

The study found that birth season influenced vitamin D levels, which makes sense since sun exposure varies by season. Maternal allergy history was also important—babies whose mothers had allergies were at higher baseline risk. The research demonstrated that vitamin D’s effect on allergy risk cannot be understood without considering a baby’s genetic makeup, as the same vitamin D level had very different effects depending on which genetic variations a baby inherited.

Previous research suggested that vitamin D plays a role in immune system development and allergy risk, but most studies didn’t examine how genes and vitamin D work together. This study advances the field by showing that genetic variations in immune-related genes determine how important vitamin D levels are for allergy prevention. The finding that both low and high vitamin D may be problematic aligns with some recent research suggesting that vitamin D’s relationship with health outcomes is complex rather than simply ‘more is better.’

The study was conducted only in Shanghai, China, so findings may not apply equally to other populations with different genetic backgrounds or environmental exposures. Vitamin D was measured only once at birth, so the study doesn’t show how vitamin D changes during pregnancy or early infancy affect allergy risk. The study identified associations but cannot prove that low vitamin D causes allergies—other unmeasured factors could be involved. The study focused on five specific genetic variations, but many other genes likely influence allergy risk. Additionally, the study didn’t measure vitamin D intake or sun exposure during pregnancy, which could have provided more complete information.

The Bottom Line

Based on this research, pregnant women should discuss vitamin D levels with their healthcare provider, particularly if they or family members have food allergies. The study suggests that a ‘one-size-fits-all’ vitamin D recommendation may not be appropriate and that individual genetic background should ideally be considered. However, this research is preliminary, and current medical guidelines still recommend adequate vitamin D during pregnancy for overall health. If you have a family history of food allergies, mention this to your doctor when discussing prenatal vitamin D supplementation. Confidence level: Moderate—this is one study in one population, and more research is needed before changing standard recommendations.

This research is most relevant to pregnant women, especially those with personal or family histories of food allergies. Parents of young children with food allergies may find this information helpful for understanding potential contributing factors. Healthcare providers caring for pregnant women and infants may use this to inform personalized counseling. This research is less immediately relevant to people without family histories of allergies, though adequate vitamin D during pregnancy remains important for overall health.

Based on this study, vitamin D’s influence on food allergy risk appears strongest in the first 6 months of life. If vitamin D deficiency is a contributing factor, correcting it during pregnancy might reduce allergy risk in the first months after birth. However, the protective effect appears to weaken by age 2, suggesting that vitamin D is just one of many factors influencing allergy development. Don’t expect vitamin D supplementation alone to prevent all food allergies, as genetics and other environmental factors also play important roles.

Want to Apply This Research?

  • If pregnant or planning pregnancy, track prenatal vitamin D supplementation dose and timing, along with vitamin D blood test results if available. Record any family history of food allergies or other allergic conditions. After birth, log any signs of food allergy reactions (rashes, vomiting, difficulty breathing) and the foods introduced, noting the timing relative to vitamin D status.
  • Work with your healthcare provider to determine your appropriate vitamin D level during pregnancy based on your individual risk factors and family history. If recommended, take prenatal vitamins containing vitamin D consistently as prescribed. If you have a family history of food allergies, discuss this with your doctor when planning vitamin D supplementation. After birth, follow your pediatrician’s guidance on introducing new foods and watch for allergy symptoms.
  • Track vitamin D supplementation throughout pregnancy and early infancy. Record any food allergy symptoms or diagnoses in your baby. Note environmental factors like season of birth and sun exposure. If your baby develops food allergies, share this information with your healthcare provider to help them understand potential contributing factors and guide management. Consider periodic vitamin D testing if recommended by your doctor, especially if you’re in a high-risk group.

This research suggests an association between vitamin D, genetic factors, and food allergy risk but does not prove causation. These findings are from one study in a specific population and should not replace personalized medical advice. Pregnant women and parents of infants should consult with their healthcare provider before making changes to vitamin D supplementation or dietary practices. Food allergy diagnosis and management require professional medical evaluation. This information is educational and not a substitute for professional medical diagnosis, treatment, or advice. Always discuss individual risk factors and appropriate vitamin D levels with your doctor.