Vitamins and Colorectal Cancer
Can Vitamin D Supplements Prevent Cancer of the Colon and Rectum?
Vitamin D, or calciferol, has generated interest over the past decade because of its possible link to colorectal cancer prevention.
The Journal of the National Cancer Institute published a study in its October 2007 issue that casts a shadow of doubt over the possible correlation of vitamin D supplements and a reduced chance of developing colorectal cancer. Cancer of the colon and rectum is the third most common cancer diagnosed in men and women, and is the third leading cause of cancer deaths in men and women, according to the American Cancer Society.
Vitamin D has a rich history of study in disease prevention, beginning with the discovery that vitamin D has an important role in the prevention of the bone-deforming disease rickets. Doctors sometimes classify vitamin D as a hormone rather than a vitamin, because humans don’t require a dietary source of vitamin D. The precursor of vitamin D resides in the skin, and exposure to ultraviolet radiation through sunlight enables the skin to manufacture vitamin D.
In addition to its known function of regulating calcium metabolism, recent research pointed to the possibility that vitamin D could have potent cancer fighting abilities. The lead author of the study, Dr. Michal Freedman, focused on the possible link between colorectal cancer prevention and vitamin D in a study of 17,000 people. The study results were mixed on the efficacy of vitamin D and cancer prevention: over the course of a decade, 536 people died of cancer, independent of their vitamin D levels. However, patients with the highest serum levels of vitamin D had a significantly lower risk of dying from colorectal cancer.
The recommended dietary allowance for vitamin D is 400 IU, or 5 micrograms, for people over the age of four. Presumably, most people should get sufficient amounts of vitamin D from regular exposure to sunlight. Doctors recommend supplemental vitamin D for housebound individuals or those in sunless climates. Dietary sources of vitamin D include fortified milk, fortified cereals, egg yolks, and liver.
If you’re thinking about taking a vitamin D supplement as a colorectal cancer preventative agent, talk to your doctor about a safe dosage. Taken in excess, vitamin D can build up in fatty tissues and cause toxicity. The exact toxic level varies, but children can experience toxic effects such as the calcification of the kidneys and other soft tissues in doses over 45 micrograms per day. You must consider anything over 25 micrograms of vitamin D per day a large dose that requires physician monitoring.
Other proven dietary links to colorectal cancer include a diet high in red meat and a diet low in vegetables. Until researchers investigate the link between vitamin D and colorectal cancer prevention further, you can make positive dietary changes by replacing that second helping of roast or steak with a serving of fresh fruits and vegetables.
Related Article: Nutrients for the Prevention of Colon Cancer
