by Paul Govern
Observational studies have associated higher levels of vitamin D in the blood with lower risk of colon cancer, but large randomized trials have found no such benefit from the use of vitamin D supplements.
A retrospective study in Clinical Nutrition by Jacklyn Hellwege, PhD, Xiangzhu Zhu, MD, Qi Dai, MD, PhD, and colleagues sheds light on associations among colon cancer/adenoma, serum levels of inactive vitamin D (25(OH)D), and serum levels of parathyroid hormone (PTH), the agent that stimulates transformation of vitamin D to its active form.
The team reports that, particularly among women, the protection afforded against colon cancer by optimal 25(OH)D levels varies according to PTH response (PTH is released as serum vitamin D levels dip). Among the many findings, women with a blunted PTH response had roughly five to six times the risk of colon cancer or adenoma.
The study involved 755 cases of colon cancer and 755 cases of adenoma, painstakingly matched with cancer-free/adenoma-free controls.
All cohorts were drawn from the National Cancer Institute’s Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Also on the study were Xiang Huang, Martha Shrubsole, PhD, Lei Fan, MD, PhD, Bingshan Li, PhD, Reid Ness, MD, MPH, Douglas Seidner, MD, Edward Giovannucci, MD, ScD, and Todd Edwards, PhD, MS. The study was supported in part by the National Institutes of Health (CA182364).
