A recent study published in the journal The forefront of nutritionUsing Mendelian randomization (MR), researchers investigated whether daily nutrient intake and serum levels of minerals, vitamins, and antioxidants were causally associated with the risk of childhood asthma (CA).
Study: Dietary intake, antioxidants, minerals, vitamins and childhood asthma: A Mendelian randomization study. Image credit: Ilike/Shutterstock
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Asthma is a chronic respiratory disease, especially in children, characterized by airway inflammation, wheezing, and bronchial reactivity. It is a growing problem worldwide, with the main risk factors being exposure to air pollutants and tobacco particles. However, diet may influence the risk of developing childhood asthma. A diverse diet reduces the risk of childhood asthma by restoring the gut microbiota. Understanding the causal relationship between nutrition and allergies is essential for the prevention and management of childhood asthma. There is limited evidence on the association between regular intake of vitamins, minerals, and nutrients and serum antioxidant levels.
About the Research
In this MR analysis, the researchers identified causal associations between childhood asthma and intake of protein, fat, carbohydrates, and sugar, as well as serum levels of vitamins, minerals, and antioxidants.
The researchers selected factors associated with normal dietary intake, including protein, carbohydrates, sugars, fats, serological antioxidant concentrations (β-carotene, lycopene, uric acid), minerals (copper, calcium, zinc, selenium, phosphorus, magnesium, iron), and vitamins (vitamins A, B6, B12, C, D, E, and folate). The researchers used these parameters as instrumental variables (IVs). The researchers obtained genetic information on childhood asthma from publicly available genome-wide association studies (GWAS) catalogs and the FinnGen database.
The research team used an inverse variance weighted (IVW) approach for data analysis. When at least three valid instrumental variables (IVs) were available, the researchers performed sensitivity analyses using three MR approaches, including weighted median (WM), MR-Egger regression (MRE), and MR multifaceted residual sum and outliers (MR-PRESSO), to explore potential biases generated by inefficient IVs.
The researchers determined odds ratios and performed independent tests by applying the Benjamin-Hochberg correction method to the false discovery rate (FDR). Individual instrumental variables such as vitamin B6 and selenium were used to derive effect estimates using the Wald ratio (WR). The research team used a fixed-effect model for the meta-analysis, which facilitated the overall risk assessment and prediction of childhood asthma.
Results and discussion
The analysis showed an inverse association between sugar intake (odds ratio 0.7) and childhood asthma risk, whereas magnesium (odds ratio 1.6), fat (odds ratio 1.4), and vitamin D (odds ratio 1.1) intakes were positively associated with increased CA risk. Meta-analysis confirmed the statistical significance of this association, consistent with results reported in several databases. Sensitivity analyses yielded similar results. The results suggest that increasing the intake of complex carbohydrates in a Mediterranean diet (MD) pattern may reduce childhood asthma risk. Compared with previous studies, the current study shows inconsistencies in the effect of sugar intake on CA levels. However, other association results are consistent with previous studies.
The current study’s researchers found a significant relationship between phosphorus and zinc in one database. In contrast, magnesium was statistically significant in the meta-analysis results of the current study, but showed no consistent trend in three additional datasets. Although the current investigation found a positive association between blood magnesium and the risk of childhood asthma, the researchers could not demonstrate a precise causal relationship between serum copper, phosphorus, and the risk of asthma. However, the results of observational studies are basically consistent with the results of the current study.
Studies have shown that fructose, found in fruit juices and beverages, is associated with metabolic abnormalities and asthma-like symptoms in non-obese mice. Diets high in fat and protein may increase the risk of childhood asthma by increasing obesity and activating inflammatory pathways. Antioxidants, such as vitamins E and C, carotenoids, ubiquinone, flavonoids, and selenium, neutralize free radicals and minimize oxidative damage that promotes airway inflammation. The exact link between antioxidants and childhood asthma is unclear, but they are essential for prevention and treatment. Vitamin D supplementation may reduce the incidence of neonatal asthma and acute asthma exacerbations in individuals with low levels.
Based on the study findings, increasing sugar intake and decreasing fat content in the diet may reduce the incidence of childhood asthma. Elevated magnesium and vitamin D levels increased the risk. However, these results were obtained from a Mendelian randomization study, and additional research is needed to confirm these correlations. Although the analysis used various data sets to establish the relationship between dietary intake, micronutrients, and childhood asthma, there are limitations such as demographic selection, IV explanatory power, and a lack of studies on intake. Further research is needed to better understand the biological pathways and improve the selection of instrumental variables.
