Multiple linear regression analysis of the seasonal changes in the serum concentration of beta-cryptoxanthin

Beta-cryptoxanthin (beta-CRX) is a carotenoid pigment found in Satsuma mandarin (Citrus unshiu Marc.) fruit, which is heavily produced in Japan. In this study, we evaluated the seasonal changes in the serum beta-CRX level and investigated predictors of serum beta-CRX level by multiple linear regression analysis. Blood tests and self-administered questionnaires were used every other month for one year. The subjects were healthy volunteers, 15 males and 12 females. The serum beta-CRX levels increased dramatically as the intake of Satsuma mandarin increased; the maximum increase was noted in January. Multiple linear regression analysis showed that, in males, the serum beta-CRX level could be predicted by Satsuma mandarin intake, age and the month of blood sampling; however, it was inversely associated with alcohol and smoking habits. Conversely, in females, the serum beta-CRX concentration could be predicted by Satsuma mandarin intake, the month of blood sampling and age; however, it was inversely associated with body mass index. The results of multiple linear regression analysis suggest that the serum beta-CRX levels can be used to evaluate the intake volume of Satsuma mandarin. Furthermore, beta-CRX is a useful biomarker to estimate the beneficial effects of Satsuma mandarin intake in epidemiological studies.