['Consensus nutritional guidelines for patients with cystic fibrosis (CF) recommend aggressive treatment of growth failure. Oral reduced glutathione (GSH) has been shown to improve cachexia and case reports have demonstrated improved growth in pediatric patients with CF. No controlled studies using oral GSH in CF have, however, been reported. The aim of the study was to determine whether oral GSH could improve growth in CF. Secondarily, to determine whether oral GSH could improve other systemic clinical markers.', 'We performed a placebo-controlled, randomized, double-blind, repeated-measures clinical trial in 44 pediatric patients with CF ages 18 months to 10 years. Primary outcomes were change in weight percentile, body mass index (BMI) percentile, height percentile, and fecal calprotectin. Secondary outcomes included liver function tests and measures of systemic inflammation. Each participant was studied for 6 months, with data obtained at baseline, 3 months, and 6 months. Blood samples were obtained on the baseline and 6-month visits. Subjects were treated with oral GSH or placebo (calcium citrate), each 65 mg · kg(-1) · day(-1) divided into 3 doses per day at mealtimes, and administered daily for 6 months.', 'The GSH treatment group gained an average of 0.67 standard deviation (SD) in weight-for-age-and sex z score (wfaszs), (19.1 weight percentile points) during the course of 6 months, with no adverse effects (vs placebo with an increase of 0.1 SD in wfaszs [2.1 weight percentile points], P < 0.0001). Fecal calprotectin improved, GSH -52.0 vs placebo 0.5), also BMI for GSH improved 0.69 SD BMI-adjusted-for-age-and-sex z score versus placebo 0.22 SD (BMI percentile 21.7 GSH vs 5.2 placebo), and height 0.2 SD in height-for-age-and-sex z score (hfaszs) GSH versus -0.06 SD hfaszs placebo [height percentile 7.0 GSH vs -2.6 placebo], all P < 0.0001). Secondary outcomes improved significantly, as well.'] Does oral reduced L-glutathione improve growth in pediatric cystic fibrosis patients?