Study design (if review, criteria of inclusion for studies)
Single centre randomized controlled trial
Participants
46 people with CF >5 years of age with diagnosis confirmed by sweat test. All participants discontinued vitamin supplementation prior to enrolment but were supplemented with vitamin E and A for 4 weeks before the trial started
Interventions
Control: continuation of low-dose supplement (10 mg vitamin E + 500 μg vitamin A) taken for 4 weeks prior to trial start. Frequency: once per day with breakfast. Duration: 8 weeks. Intervention: 200 mg vitamin E (RRR a-tocopherol), 300 vitamin C (sodium ascorbate), 25 mg β-carotene, 90 μg selenium (selenomethionine), 500 μg vitamin A (retinyl palmitate in oil).
Outcome measures
Lung function (FEV1 % predicted), quality of well being, lipid peroxidation, plasma antioxidant status, plasma fatty acid status, pulmonary exacerbations measured at 0 and 8 weeks.
Main results
Antioxidant defenses in group B improved, whereas those in group A did not: in groups B and A, the mean (+/- SEM) changes (Delta) in vitamin E were 10.6 +/- 1.5 and -1.9 +/- 0.9 micro mol/L, respectively (P < 0.001), (Delta)beta-carotene were 0.1 +/- 0.04 and -0.01 +/- 0.02 micro mol/L, respectively (P = 0.007), (Delta)selenium were 0.51 +/- 0.10 and -0.09 +/- 0.04 micro mol/L, respectively (P < 0.001), and (Delta)glutathione peroxidase activity were 1.3 +/- 0.3 and -0.3 +/- 0.6 U/g hemoglobin, respectively (P = 0.016). There were no significant differences between the groups in Delta8-iso-PGF(2)(alpha), (Delta)vitamin C, (Delta)fatty acid composition, (Delta)superoxide dismutase activity, (Delta)lung function, or (Delta)white cell count. Within group B, (Delta)beta-carotene correlated with (Delta)percentage of forced vital capacity (r = 0.586, P = 0.005), (Delta)selenium correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.440, P = 0.046), and (Delta)plasma fatty acid concentrations correlated with (Delta)percentage of forced expiratory volume in 1 s (r = 0.583, P = 0.006) and Delta8-iso-PGF(2)(alpha) (r = 0.538, P = 0.010).CONCLUSIONS
Authors' conclusions
Whereas increased beta-carotene, selenium, and fatty acid concentrations are linked to improved lung function, increased plasma fatty acid concentrations are linked to oxidative stress. If oxidative stress is deemed to be important to the clinical outcome of CF patients, means of reducing oxidative stress while maintaining a high-fat, high-energy diet must be investigated.