High levels of vitamin D in the blood may help prevent colorectal cancer, according to results from a large medical investigation published Thursday.
The new results have produced the most powerful evidence to date that high levels of vitamin D in the blood help prevent the disease that is a leading cause of cancer deaths, one researcher in the study said. The new data adds clarity to earlier, smaller studies with mixed results about the vitamin’s role in reducing risk.
The hope, experts said Thursday, is that the new research, published in The Journal of the National Cancer Intitute, will help sway panels that advise the public how to lower cancer risk.
Doctors on Long Island not associated with the analysis said the findings are probably not the last word on the subject.
Dr. Rajiv Datta, medical director of the Gertrude and Louis Feil Cancer Center in Valley Stream, said there is no established level of vitamin D known to prevent colorectal cancer.
“Can the vitamin prevent polyp growth? That’s an important question,” said Datta, referring to the abnormalities in the large intestine that lead to tumors.
Because there are no guidelines on an optimal dose of vitamin D to prevent any cancer, scientists in the study relied on the vitamin’s only established one for bone health.
“The current recommendation for vitamin D is based solely on bone health because that’s where most of the evidence has been,” said Marji McCullough, senior scientific director of epidemiology at the American Cancer Society’s headquarters in Atlanta. “The new vitamin D data strengthens our previous information that the vitamin lowers colorectal cancer risk.
“Our research also provides information for future review panels, such as the National Academy of Medicine and other organizations that publish guidelines on cancer risk reduction,” McCullough said.
The investigation involved medical researchers from the American Cancer Society, Harvard University’s T.H. Chan School of Public Health, the National Cancer Institute, and more than 20 medical centers and health organizations in this country and abroad.
Vitamin D is often called the “sunshine vitamin” because it can be obtained by exposure to sunlight. Deep green leafy vegetables, dietary supplements and vitamin D-fortified foods are other sources of the nutrient.
The form of vitamin D sought in the massive analysis, which involved 5,700 people with colorectal cancer and 7,100 without the disease, was 25-hydroxyvitamin D, the key form that circulates in the blood.
To maintain bone health the academy recommends a daily dose of 600 international units of vitamin D from childhood through age 70. After age 70, the recommendation is 800 daily international units.
“The range we found associated with the lowest risk is 75 to 100 nanomoles of vitamin D per milliliter of blood,” McCullough said.
People who had blood concentrations of vitamin D lower than those recommended for bone health had a 31 percent higher risk of colorectal cancer. Those whose blood had higher than the recommended level of the vitamin had a 22 percent lower risk of the cancer, according to the analysis.
“I would say this is an important study because if the findings are true, then we can potentially impact the treatment of patients who have lower levels of vitamin D,” said Dr. Toyooki Sonoda, chief of the division of colon and rectal surgery at NYU Winthrop Hospital in Mineola.
The aim of studies of this kind is to understand what is happening biologically among people at average risk for the disease, Sonoda said.
He called colorectal cancer a complex disorder that is a major public health concern.
“It remains the third most common cause of cancer and cancer-related deaths in both men and women,” Sonoda said, noting that the disease in recent years has been rising among people in their 20s through early 40s.
McCullough, noted meanwhile, that vitamin D is intricately involved in cell function, which may help explain its role as a cancer preventive.
“In experimental studies vitamin D has been shown to control cell proliferation and possibly the spread of abnormal cells. Cancer is the result of abnormal cell growth,” McCullough said.
Asked how the public should interpret the new research, McCullough said the findings on vitamin D should be taken as one of multiple steps to prevent colorectal cancer, the third leading cause of cancer in the United States.
She identified the other measures as consuming a healthy diet, maintaining a healthy body weight, limiting alcohol intake, avoiding red meat and exercising regularly.
“The maximum benefit is from doing all of these things,” McCullough said.
Doctors and other researchers involved with the new analysis said they were providing evidence that confirms the vitamin lowers the cancer risk, not crafting guidelines with their findings.