Boosting the omega-3 levels in a pregnant woman's blood may lower her child's risk of developing asthma, suggests a groundbreaking study from Denmark. This evidence adds to the growing support for universal DHA supplementation among pregnant women. According to the CDC, asthma affects 8.6% of children under 18 years old (6.3 million) in the U.S. alone, costing approximately $56 billion annually.
As the leading chronic disease in children, the main cause of missed school days, and the third leading cause of hospital stays for children, asthma represents a significant concern for both children and adults. Simple dietary changes that can decrease the occurrence of wheezing or asthma would significantly enhance overall quality of life and reduce healthcare costs. This study aimed to determine whether maternal supplementation with EPA+DHA during the third trimester could improve outcomes of wheezing and asthma in infants compared to a placebo.
"Gold standard" study design and methods
This single-center, double-blind, randomized, placebo-controlled trial recruited generally healthy pregnant women around the halfway mark of pregnancy (22-26 weeks). By week 24 of pregnancy, 736 women were randomly assigned to either take 2400 mg per day of long-chain omega-3s (55% EPA and 37% DHA) or a placebo (olive oil) until one week post-delivery. The researchers measured maternal blood levels of EPA+DHA at baseline and one week after delivery. Breast milk was also collected one month post-delivery and analyzed for EPA+DHA levels. Pediatricians, blind to the patient's assigned group, collected information during clinical visits for up to 5 years. The primary endpoint was "persistent wheezing" (till the child was 3 years old) and "asthma" (after 3 years; "asthma" will be used to describe both in this article). Additionally, the study was fully funded by the Danish government, and the fish oil capsules were not donated, enhancing the credibility of the findings and their interpretation.
EPA + DHA blood levels increased in supplemented women
As expected, fish oil supplementation resulted in increased blood levels of EPA+DHA compared to a decrease in the placebo group. This reduction in the placebo group is anticipated since other studies have shown that maternal blood levels decrease throughout pregnancy if not supplemented with EPA+DHA, presumably due to the transfer of these fatty acids to the developing fetus. It's worth noting that the normal dietary intake of EPA+DHA was "high" in this Danish study population compared to American mothers, contributing to a higher baseline estimated Omega-3 Index than average American women of childbearing age.
Asthma risk reduced by over 50% in children of women with low Omega-3 levels before supplementation
Across the study cohort, a significant portion of children was diagnosed with asthma. The supplemented group saw a notably lower diagnosis rate compared to the placebo group, representing a relative risk reduction. This preventive effect appeared primarily in children of mothers with the lowest blood levels of EPA+DHA at baseline. Further analyses indicated that EPA+DHA supplementation was effective in reducing asthma risk in women with a baseline blood level of EPA+DHA up to a certain percentage, suggesting a potentially greater impact on asthma frequency if the study were conducted in the U.S., where average Omega-3 Index levels are lower.
Breast milk EPA+DHA less reliable predictor for asthma risk
No correlation was found between levels of EPA+DHA in breast milk postpartum and the later development of asthma; however, there was a trend in the control group with increased EPA+DHA levels in breast milk. The reasons behind these findings could be speculative, considering that breast milk levels of EPA+DHA can quickly adjust to new levels based on diet.
The study's lead author Dr. Bisgaard suggested that pending further studies, testing women for their blood fatty acid levels to identify those who could benefit from fish oil supplementation might be the best way to apply these findings.
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