Giovannucci, Edward LKim, Hanseul2022-03-1820222022-03-172022-03Kim, Hanseul. 2021. Vitamin D, calcium, and early-onset colorectal neoplasia. Doctoral dissertation, Harvard University Graduate School of Arts and Sciences.28962348https://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37371118Colorectal cancer (CRC) incidence among individuals younger than age 50 has been increasing. Although the overall CRC incidence has been decreasing in many parts of the world, early-onset CRC (defined as CRC diagnosed before age 50) has been increasing at an alarming rate. Unlike the traditional CRC that is well-studied and associated with many risk factors, early-onset CRC has not been studied much and has no simple explanation for its causes. In Chapter 1, we examine vitamin D intake in relation to early-onset CRC. Vitamin D has consistently been studied with CRC risk. In addition, the recent increase in early-onset CRC incidence temporally overlaps with vitamin D deficiency around the world. Thus, we hypothesized that vitamin D could be related to early-onset CRC risk. In Chapter 2, we assess vitamin D intake in relation to early-onset conventional adenoma and serrated polyp. Conventional adenoma and serrated polyp are precursors to cancer, so studying them help understand about CRC. We therefore evaluated whether vitamin D is associated with early-onset conventional adenoma and/or serrated polyp among those who underwent at least 1 lower endoscopy. In Chapter 3, we evaluate the association between calcium and early-onset CRC. Calcium and vitamin D are often studied together because they are both nutrients essential for bone health. Moreover, in experimental studies, they have been studied to have anti-cancerous properties. The World Cancer Research Fund/American Institute for Cancer Research concluded calcium as having strongly probable evidence of a causal inverse association with CRC risk. However, the association between calcium and early-onset CRC has not been studied before. Therefore, we investigated the association between calcium, dairy foods, and early-onset CRC risk. Our findings suggested that increasing vitamin D and calcium intake could be encouraged for CRC prevention among individuals younger than age 50.application/pdfenEpidemiologyThesis or Dissertation2022-03-180000-0002-5102-6118