Nutritional and Biochemical Effects of Orange Juice Supplementation in Soccer Players: a Double Blind, Randomized and Controlled Trial

Thirty-four male soccer players aged 18.5 ± 0.5 years and BMI (Body Mass Index) of 21.41 ± 1.48 kg/cm2 were randomly divided into two parallel groups: (1) orange juice (n = 17), composed of individuals receiving 1 liter/day of orange juice; (2) control (n = 17) composed of individuals receiving 1 liter/day of control drink with the same proportion of total sugars as the orange juice. The recruitment process began in September 2013, the intervention was carried out from November 2013 to January 2014, and the data analysis started in February 2014. The sample size took into account the variances in total cholesterol, considering the high statistical variability of biochemical markers, which requires a sufficient number of samples to ensure representativeness and adequate statistical power of analysis, and that the reduction of total cholesterol is associated to the regular consumption of orange juice (Dourado et al., 2015). Based on unpublished data from a previous pilot experiment, it was expected that the total cholesterol of orange juice group would be 10% lower in relation to control group after intervention (orange juice = 123.41 ± 12.12 mg/dL, control drink = 37.80 ± 11.17 mg/dL). Thus, with a type I error α = 0.05 and a type II error β = 0.2 (80% power) the minimum sample size should have 12 individuals per group (n = 24). Considering the high layoffs rate in the team, the initial sample size of study was constituted by 17 individuals per group (n = 34). During the intervention, four individuals from control drink group failed the study protocol, and the study was concluded with 30 participants (orange juice n = 17 and control drink n = 13). Primary and secondary endpoints were the improvement of food intake and changes in biochemical markers, respectively. Shapiro Wilk and Levene tests evaluated normality and homogeneity of data, respectively. T-test was conducted to identify possible differences between groups at baseline. A mixed factorial ANOVA was applied to determine the effect of treatment and time, within and between groups (Sidak post hoc test), and statistical significance was set at p < 0.05. Food intake, biochemical biomarkers and body composition were assessed before and after the 60 days of intervention.