Babies fed blueberries show fewer allergy symptoms and boosted immune balance

Feeding blueberries to infants in the first year of life may help alleviate allergy symptoms and alter immune responses, suggesting a new dietary approach in infant health research.

Study: Blueberry Consumption in Early Life and Its Effects on Allergy, Immune Biomarkers, and Their Association with the Gut Microbiome. Image Credit: SoNelly / Shutterstock 

In a recent study published in the journal Nutrients, researchers examined the impact of blueberry intake in early life on allergy-related symptoms, gut microbiota, and immune biomarkers. The complementary feeding period represents a critical time frame for shaping infant immune development, diet, and gut microbiota.

Current recommendations suggest introducing a range of plant-based foods from six months of age, in conjunction with continued breastfeeding. Growing evidence supports a role for blueberries in the microbiota-inflammation-immunity axis and gut microbial homeostasis.

The first year of life is a critical window for establishing immune competence and preventing allergic diseases. Dietary exposures during this period can influence the induction of immune tolerance, epigenetic programming, and gut microbial succession.

Suboptimal or aberrant microbial colonization has been linked to increased gut permeability, impaired innate immune responses, and low-grade inflammation, all of which are associated with a higher risk of diseases in later life.

About the study

In the present study, researchers investigated the effects of early-life blueberry intake on allergy-related symptoms, gut microbiota, and immune biomarkers. This randomized, double-blind, placebo-controlled trial recruited participants from households with infants aged 3 to 4 months.

Term-born infants were included if they were healthy, exclusively breastfed, and had no prior exposure to complementary foods. Infants were randomized to a blueberry or a placebo group.

The blueberry group received blueberry powder at 10 g per packet, while the placebo group received a color- and flavor-matched, isocaloric powder. Caregivers were instructed to offer one packet daily from baseline to 12 months (of age), and avoid other forms of blackberries or blueberries throughout the intervention. Infant blood and stool samples were collected at several time points. 16S rRNA gene sequencing was performed to assess gut microbial profiles.

The team analyzed 29 chemokines and cytokines, as well as their associations with microbiota characteristics. Caregivers were asked whether their child had any respiratory symptoms, such as whistling or wheezing in the chest, dry cough unrelated to chest infection or cold, nasal symptoms unrelated to cold, skin-related concerns (e.g., itchy skin), gastrointestinal symptoms, or other symptoms indicative of an allergic reaction, at each study visit.

Baseline characteristics were compared using analysis of variance (ANOVA) and Fisher’s exact tests. Kruskal-Wallis tests were used to compare differences in cytokines/chemokines between groups. Correlations between cytokines and bacterial taxa were examined using Kendall’s rank correlation test.

Furthermore, linear regression modeling was performed to investigate the associations between interleukin-10 (IL-10) and IL-13 and bacterial taxa, while accounting for treatment group and covariates.

Findings

The study randomized 38 infants to receive the blueberry powder and 37 to the placebo group; of these, 29 and 31 infants completed the intervention, respectively, and were included in the final analytic sample. The paper also reported that 61 infants (30 blueberry, 31 placebo) completed the study overall; however, the final analyses used 60 infants (29 blueberry, 31 placebo).

Both groups had similar baseline characteristics, with a mean age of 22 weeks at enrolment. Vaccination rates were high in both groups.

No infant in either group received cough suppressants, antibiotics, or had feeding concerns at baseline. Respiratory symptoms were significantly different between groups at baseline. In the blueberry group, seven infants had some respiratory symptoms, and four had a history of dry cough. Conversely, the placebo group had no such symptoms.

Longitudinal analysis of allergy symptoms revealed significant differences in the trajectories of respiratory (p = 0.02) and overall allergic symptoms (p = 0.05). Four subjects in the blueberry group had respiratory symptom resolution, with fewer developing new symptoms during the follow-up, compared to the placebo group.

Although the blueberry group had more respiratory symptoms at baseline, a greater number of infants in the blueberry group achieved symptom resolution by the end of the study compared to the placebo group.

Most cytokines did not show significant differences between groups. IL-13 was lower in the blueberry group than in the placebo group in a small, sensitivity analysis without imputation (n≈7 per group; p=0.035), and IL-10 was borderline higher in the blueberry group (p=0.052).

Cytokine analyses were only available for 48 infants, which limited the statistical power. Changes in allergy symptoms were not significantly associated with IL-10 or IL-13.

In total, 32 cytokine-bacteria associations, involving 18 bacterial groups and 19 cytokines, were reported. IL-10 levels were positively associated with Megasphaera, Clostridiaceae, and Lactobacillus at 12 months. IL-10 showed negative associations with Peptostreptococcaceae, Blautia, and Lacticaseibacillus at 12 months.

IL-13 levels were positively associated with Clostridia and Citrobacter, and negatively associated with Peptostreptococcaceae, Lactobacillus, Blautia, and Anaerostipes at 12 months.

These microbiota–cytokine associations were exploratory and not adjusted for multiple comparisons, so they should be considered hypothesis-generating.

Conclusions

In summary, the findings indicate that blueberry intake during infancy may influence the resolution of allergic symptoms and modulate immune development.

The associations of immune markers, such as IL-10 and IL-13, with specific bacterial taxa highlight potential targets for further mechanistic investigations. However, the cytokine analyses were limited by small sample sizes and missing data, and the study was not designed to detect clinical endpoints. 

Additional studies are needed to explore the specific blueberry components driving these effects and investigate whether other complementary foods can confer similar benefits.