Comments on adolescent intakes of vitamin D and calcium and incidence of proliferative benign breast disease

Abstract

We read with great interest the article by Su et al. [1] published in May 2012. This retrospective study reported some interesting observations and discussions on vitamin D intake and incidence of proliferative benign breast disease from a large population. However, we feel that it might be necessary to discuss some concerns on the methods and conclusions out of interpretation in this study. Recently, some interesting articles about the associations between the vitamin D and breast diseases have been published in this journal [2–8]. However, vitamin D intake does not represent the extent of vitamin D deficiency, which is mostly defined by the serum vitamin D level (25(OH) D.\20–30 ng/mL) [2, 3, 6, 9]. Because vitamin D deficiency is related to dietary, sun exposure, and/or metabolic factors: 20 % vitamin D is obtained from food (fish, eggs, animal livers, dairy products), while 80 % from skin synthesis as a product of skin 7-dehydrocholesterol transformations, induced by ultraviolet radiation [10]. In their study, it might be unreliable to use vitamin D intake to determine the associations between vitamin D status and incidence of proliferative benign breast disease. We believe that the sun exposure should be taken into consideration as covariate, and also the true serum vitamin D levels should be included for sample grouping as previous studies conducted [2, 3, 11, 12]. If these analyses could not be conducted, these confounding factors should be welldiscussed in this article. Another point is that whether lifestyles of the subjects were changed after high school. If the lifestyles were changed significantly, researchers may consider its influence when drawing the final conclusions. We believe that information on these issues mentioned above would, with no doubt, help readers understand the findings of this article more clearly.