Can vitamin D effectively treat colorectal cancer that has spread in the body? The answer is, we don’t know, but preliminary research has shown some promise.

Atlantic Health System is part of a nationwide phase 3 study on vitamin D’s impact in treating patients with stage 4 colorectal cancer. It will involve more than 1,000 patients enrolled through the spring of 2022. Participants receive the chemotherapy combination FOLFOX, a standard treatment of care, with either a standard dose of vitamin D or a high dose of the vitamin. A small clinical trial demonstrated benefits for patients, leading to the phase 3 research.

The question of whether vitamin D can decrease growth of colon cancer cells is an intriguing one, but we also have to ask, is there any potential for harm? The study addresses that too.

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Colorectal cancer is the third leading cause of cancer-related deaths in the U.S. and the third most common cancer in men and in women (excluding skin cancers), according to the Centers for Disease Control and Prevention. The American Cancer Society estimates 149,500 new cases will be diagnosed in 2021.

Colonoscopy screenings have reduced the incidence of colorectal cancer in people age 50 and older since the mid-1980s, but rising cases among younger adults led the American Cancer Society in 2018 to recommend 45 as the age for people with average risk to begin getting screened — five years younger than prior guidelines recommended.

Colorectal cancer typically begins as small, benign polyps that form in the large intestines and mutate. Colonoscopies can locate polyps for removal before they become cancers.

Colonoscopy screenings have dipped during the COVID-19 pandemic, which is a significant concern. When caught early, colon cancer has a 91% five-year survival rate. If it spreads to distant parts of the body, the survival rate drops to 14%, according to the American Cancer Society.

Studies have shown that low vitamin D levels are associated with an increased risk of colorectal cancer (as well as other cancers). Based on the data, I suggest people have their vitamin D level tested, in consultation with their doctor. If it is below normal, they can take supplements to get the level into the normal range. There is no evidence that doing so would cause harm when appropriately monitored.

Stay healthy, get annual checkups, and listen to your body. If you feel something is not right, get it checked out.

To learn more about the study and the large portfolio of colorectal cancer studies at Atlantic Health System, visit


Sophie Morse, MD, MSC is the principal investigator for Atlantic Health System’s role in a nationwide phase 3 study on vitamin D’s impact in treating patients with stage 4 colorectal cancer. A gastrointestinal oncologist at Atlantic Health System’s Overlook Medical Center, Dr. Morse is board certified in hematology, medical oncology, and internal medicine.