Vitamin D lowers risk of cancer: Study
Colorectal disease lower with high concentrations
Higher concentrations of vitamin D circulating in the bloodstream are linked to a lower risk of colorectal cancer, according to a large international study published Thursday.
The researchers said the results strengthen the evidence that the vitamin may play a protective role against the disease, which is the third-most common cancer in the United States, killing more than 50,000 people a year.
Previous studies exploring a possible link were inconclusive, they said.
The latest research, which appears in the Journal of the National Cancer Institute, was conducted by scientists from NCI, the American Cancer Society, the Harvard T.H. Chan School of Public Health and 20 other medical centres and organizations around the world.
They concluded that “optimal” levels of the vitamin for colorectal cancer prevention are greater than those recommended by the National Academies of Sciences, Engineering and Medicine, which are based only on bone health.
“Our study shows that having higher levels above bone-health ones are associated with lower colorectal cancer,” said Stephanie Smith-Warner, a Harvard epidemiologist and one of the senior authors of the article.
The researchers found people who had lower levels of vitamin D than recommended by the National Academies for bone health had a 31% higher risk of colorectal cancer during a followup period that averaged 51/2 years.
Sources of vitamin D include exposure to the sun, fatty fish such as salmon and trout, foods such as milk and orange juice fortified with the vitamin and dietary supplements. Experts say diet is the best way to get vitamin D because sun exposure raises skin cancer risks.
The lifetime risk of colorectal cancer is 1 in 24 in women and 1 in 22 in men.
Overall, the rate of colorectal cancer is declining, but is increasing among younger people, a trend that recently prompted the American Cancer Society to recommend screening for the disease starting at age 45, not 50.