Higher Intakes of Omega-3 Associated with Less Asthma in Young Adults
Li, J. et al., Amer. J. Clinical Nutrition , 97: 173-178 , 2013
Dept. of Epidemiology and Nutrition, Univ. of North Carolina at Chapel Hill, Chapel Hill, North Carolina ,USA
Asthma is a common chronic condition involving inflammation of the airways due to environmental, genetic, and other factors. The disease afflicts approx. 300 million people globally and is characterized by episodes of wheezing , coughing, shortness of breath, and chest tightness. Since the long-chain omega-3 fatty acids (EPA plus DHA) have been shown to have significant anti-inflammatory effects, it was of interest for this research group to study the possibility that higher intakes of these omega-3 PUFA (polyunsaturated fatty acids) , namely EPA (eicosapentaenoic acid ) plus DHA (docosahexaenoic acid) plus DPA (docosapentaenoic acid) combined, may have beneficial effects on the development of asthma.
For this purpose, 4162 participants (ages 18-30) who were free of asthma at baseline were followed for 20 years along with assessments of their fatty acid intakes by FFQ (food frequency questionnaires) and nutrient/compositional databases. The results were adjusted to balance for potential confounding variables such as sociodemographic, lifestyle, dietary. During the study period, 11.2 % of the young adults developed asthma as diagnosed by a physician or by the use of medicinal treatment to help control the asthma. Higher intakes of (EPA plus DHA plus DPA) were found to be associated with a considerably lower incidence of asthma such that those in the highest ‘quintile’ (top 20 %) with respect to long-chain omega-3 intakes had a 54 % lower development of asthma when compared to those in the lowest ‘quintile’. The average daily intake of long-chain omega-3 per person was 410 mg while that in the other four groups averaged 30-190 mg (with 30 mg being in the lowest ‘quintile’). While both EPA and DHA intakes (if higher) were inversely related to the incidence of asthma , a somewhat greater benefit for DHA emerged from the statistical analyses as reported by the authors.
Dr. Holub's Comments:
While the mechanisms underlying the apparent beneficial effects of EPA and DHA were not studied herein , both have been found to suppress the formation of pro-inflammatory products (including ‘cytokines’) in other studies with DHA showing a stronger effect in some of these. Current daily intakes of (EPA plus DHA) in the US are approx. 125-150 mg/day such that a 2- to 3-fold increase in intake would be needed to reach a target of 400 mg/day or more. It remains to be determined via randomized/controlled clinical trials if supplementation can offer similar apparent protective benefits in reducing the incidence of asthma as suggested by dietary EPA/ DHA in the present study.