ATLANTA – Increasing maternal postpartum–plasma alpha-tocopherol isoform concentration was associated with a decreased likelihood of wheezing at age 2 years, defined as wheezing in the past 12 months, use of asthma medications in the past 12 months, or diagnosis of asthma, results from a large analysis showed.
“For now, this is an association and not causation,” study author Cosby Stone, MD, MPH, said in an interview in advance of the annual meeting of the American Academy of Allergy, Asthma, and Immunology. “We need a clinical trial to evaluate the effect of giving more alpha-tocopherol to mothers during pregnancy before anyone should jump to giving supplements.”
Dr. Cosby Stone
The median age of children at the time of maternal sample collection was 50 days. 47% were female, and 61% were white. Of the 652 children, 167 (26%) met criteria for wheezing at age 2 years. These children had mothers with significantly lower postpartum concentrations of plasma alpha-tocopherol, compared with those who did not meet criteria for wheezing at 2 years (a mean of 69 micromol/L vs. 75 micromol/L, respectively; P = .02). In multivariable regression analysis, the researchers detected a significant interaction between gamma-tocopherol and alpha-tocopherol, where the highest amounts of maternal gamma-tocopherol modified and mitigated the protective association of maternal alpha-tocopherol with risk of wheezing at 2 years (P = .05).
Dr. Stone cautioned that, what is currently labeled as vitamin E or alpha-tocopherol in foods and supplements, “could be any of eight different isoforms, and alpha-tocopherol may not actually be the dominant isoform being provided. In addition, the oils that we eat are the main sources of tocopherols in our diet, and they vary widely in terms of their tocopherol isoforms. Sunflower and safflower oil, for example, provide predominantly alpha-tocopherol as their isoform of vitamin E, while corn and soy oil provide predominantly gamma-tocopherol.”
For now, he continued, correcting maternal alpha-tocopherol deficiency, currently defined by a serum alpha-tocopherol concentration less than 11.6 micromol/L, is certainly reasonable. Down the road, modification of maternal alpha-tocopherol or gamma-tocopherol concentrations through dietary counseling may provide clinicians with a tool to prevent wheezing or asthma in affected children. “In the future there may be a role for checking tocopherol isoforms in pregnant women and then modifying dietary oil consumption to protect the health of their children,” he said.
He acknowledged certain limitations of the study, including that researchers obtained maternal vitamin E isoform measurements at enrollment, when the infants were, on average, 6 weeks post partum, and not during pregnancy. “However, the literature has shown that postpartum vitamin E levels at this time point are very similar to those during the second trimester of pregnancy,” Dr. Stone said. “The literature has also shown that plasma vitamin E isoform concentrations are tightly tied to diet and body stores and do not change very rapidly (such that a woman would not be likely to go from the highest quartile to the lowest, or vice versa). People’s diets don’t tend to change that much, in general.”
INSPIRE is funded by the National Institutes of Health. Dr. Stone is funded by an NIH training grant through Vanderbilt University. He reported having no relevant financial disclosures.