A new study from the American Cancer Society, the Harvard T.H. Chan School of Public Health and the U.S. National Cancer Institute has found that higher blood vitamin D concentrations are significantly associated with a lower risk of colorectal cancer. The study strengthens the evidence, previously considered inconclusive, for a protective relationship.
Optimal vitamin D concentrations for colorectal cancer prevention may be higher than the current National Academy of Medicine recommendations, which are based only on bone health.
Vitamin D, known for its role in maintaining bone health, has been thought to guard against colorectal cancer via several ways.
The study analyzed participants’ data, collected before colorectal cancer diagnosis, from 17 prospective studies. The analysis included over 5,700 colorectal cancer cases and 7,100 controls from the United States, Europe, and Asia.
Compared to participants with circulating vitamin D concentrations considered sufficient for bone health, those with deficient concentrations of vitamin D had a 31% higher risk of colorectal cancer during the follow-up period of 5.5 years.
Participants with vitamin D blood concentrations above those recommended for bone health were 22% less likely to develop colorectal cancer. These associations persisted even after adjusting for known colorectal cancer risk factors. The risk of colorectal cancer, however, did not continue to decline at the highest vitamin D concentrations.
The link between vitamin D and cancer risk was noticeably stronger in women than men at concentrations above bone health sufficiency.
Vitamin D can be obtained in the diet, particularly from fortified foods (e.g., milk) and fatty fish, from supplements and from sun exposure. In Canada and the northern U.S., it’s recommended that people take a vitamin D supplement (800 IU to 2000 IU) daily to maintain a sufficient blood vitamin D level.
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