Purpose: Conjugated linoleic acid (CLA) has been reported to modify the inflammatory response associated with allergic airway disease, primarily in animal models. To extend these observations to humans, the effect of short-term CLA supplementation on the severity of exercise-induced bronchoconstriction (EIB) was investigated in asthmatics.
Methods: Six subjects with physician-diagnosed asthma and EIB began the study on their usual diet, to which was added 4.8 g CLA/d for 8 wk. Pulmonary-function tests were administered before and after eucapnic voluntary hyperventilation (EVH) challenge at the commencement (Week 0) and conclusion of the treatment period (Week 8). Pre- and 90 min post-EVH challenge, urine was assayed for the presence of cysteinyl leukotrienes (LT) C4-E4 and 9α, 11β-prostaglandin (PG) F2.
Results: Pre- to post-EVH forced expiratory volume in 1 s (FEV1) did not significantly differ (p > .05) from Week 8 to Week 0. The pre- to post-EVH decline in FEV1 at Week 8 (-29.6% ± 6.6%) was not significantly different (p > .05) from that at Week 0 (-32.0% ± 5.5%). Area under the curve of FEV1 plotted against time from zero to 60 min (AUC0-60) was unaltered at Week 8 (-931% ± 350% change per minute) compared with Week 0 (-1,090% ± 270% change per minute). CLA supplementation did not alter forced midexpiratory flow, forced vital capacity (FVC), or FEV1/FVC. In addition, post-EVH urinary LTC4-E4 and 9α, 11β-PGF2 were unchanged after CLA supplementation.
Conclusion: Daily supplementation of 4.8 g CLA for 8 wk does not attenuate airway inflammation or hyperpnea-induced bronchoconstriction in asthmatic individuals.