Bone Growth in Childhood and Adolescence: The Interpretation of Dietary Supplementation Trials

Abstract

The interpretation of nonrejection of the null hypothesis is examined in the context of dietary supplementation trials in children and adolescents. A number of randomized controlled trials have been conducted to investigate if additional dietary calcium in the form of supplements or dairy products influences bone mineral accrual in children and adolescents. The results of these trials have been positive, showing an increment in the bone mineral gain of the supplemented group compared to the control group. The bone mineral status of the two groups was then compared after subjects returned to their normal diet, usually 18 months to 2 years after supplementation was withdrawn. In all the trials, the bone status measures of the two groups were judged to be similar because the p-value was greater than 0.05 and the null hypothesis was not rejected. The usual interpretation was that the previous benefit of an increase in bone mineral status in the supplemented group was lost after withdrawal of supplementation. It is argued in this paper that such an interpretation of the results of the statistical testing is not valid, because failure to reject a null hypothesis does not automatically imply that it should be accepted.