Fig. 1From: Vitamin D supplementation as a potential cause of U-shaped associations between vitamin D levels and negative health outcomes: a decision tree analysis for risk of frailtyA decision tree by classification and regression tree analysis based on use of vitamin D supplement and 25-hydroxyvitamin D (25 (OH) D) among 238 male veterans in a nursing home. 25 (OH) D: 25-hydroxyvitamin DBack to article page