Effects of β-carotene supplementation for six months on clinical and laboratory parameters in patients with cystic fibrosis

BACKGROUND—Patients with cystic fibrosis (CF) have significantly decreased plasma concentrations of nutrient antioxidant vitamins, especially of β-carotene, which is thought to result from fat malabsorption and chronic pulmonary inflammation. The aim of this double blind, placebo controlled study was to investigate the effect of oral β-carotene supplementation for six months on clinical parameters.
METHODS—Twenty four patients with CF were randomised to receive β-carotene 1 mg/kg/day (maximum 50 mg/day) for three months (high dose supplementation) and 10 mg/day for a further three months (low dose supplementation) or placebo. At monthly follow up visits the plasma β-carotene concentration, total antioxidant capacity, malondialdehyde (MDA) as a marker of lipid peroxidation, and clinical parameters (Shwachmann-Kulczycki score, body mass index (BMI), height, and lung function (FEV₁)) were assessed. The number of pulmonary exacerbations requiring antibiotic treatment (in days) three months before and during the study were evaluated.
RESULTS—The plasma concentration of β-carotene increased significantly to the normal range during the three months of high dose supplementation (baseline 0.08 (0.04) µmol/l to 0.56 (0.38) µmol/l; p<0.001) but decreased to 0.32 (0.19) µmol/l in the period of low dose supplementation. Initially raised plasma levels of MDA fell to normal levels and the total antioxidant capacity showed a non-significant trend towards improvement during high dose supplementation. Antibiotic treatment decreased significantly in the supplementation group from 14.5 (14.9) days/patient during the three months before the study to 9.8 (10.3) days/patient during high dose supplementation (p=0.0368) and to 10.5 (9.9) days/patient during low dose supplementation, but increased in the placebo group. The Shwachmann-Kulczycki score, lung function, and BMI did not show any changes in either of the treatment groups. No adverse events were observed during the study period.
CONCLUSION—Oral β-carotene supplementation in a dose of 1 mg/kg/day only was effective in normalising the plasma concentration of β-carotene and resulted in a decrease in pulmonary exacerbations. These data suggest that patients with CF may benefit clinically from supplementation with β-carotene and further studies are warranted.