"D" Is for "Don't Know Yet": D₃ & Prostate Cancer Prevention
Should men concerned about prostate cancer take Vitamin D₃ supplements?
A new pilot study indicates that Vitamin D₃ supplementation after a prostate biopsy reduced inflammation and might prevent low-grade prostate tumors from becoming aggressive—but there’s much more to the story.
Behind the Scenes of the Study
In March 2015, Dr. Bruce Hollis, from Medical University of South Carolina in Charleston, presented his team’s research and findings at the American Chemical Society’s National Meeting and Exposition.
Thirty-seven men who’d been scheduled to undergo elective prostatectomy (the surgical removal of the entire or part of the prostate gland) either received 4,000 IUs of vitamin D₃ or a placebo daily in the two-month period between their initial biopsies and scheduled surgeries. Typically, doctors wait two months before operating to allow the inflammation caused by the biopsy procedure to subside.
After the mens' surgery, the study team evaluated the prostate glands. "We saw some really incredible molecular changes… in glands from men who had taken vitamin D₃," Dr. Hollis says. He explains: "The number 1 gene that showed up on the heat map was growth differentiation factor 15 [GDF-15]…Treatment with vitamin D, at 4000 IU per day, turns GDF-15 gene expression up, and that inhibits inflammatory processes. "In one small prostate cancer study, taking vitamin D shrank the tumors or made the cancer disappear in greater than 60% of patients.Reducing inflammation is important because "cancer is associated with inflammation, especially in the prostate gland," Hollis says. Previous studies show that the protein GDF15 dials down inflammation, and many aggressive prostate cancers make little or no GDF15.
Notably, Hollis found that "in greater than 60% of those taking it, vitamin D actually made the cancer better." In some cases the tumor shrank; in others the cancer went away. The tumors in the placebo group remained the same or got worse.
3 Major Study Limitations
However, there’s a lot we don’t know about the accuracy and applicability of these findings.
1First, the study’s small sample size—37 men—is considerably too meager to apply to the general population, as Dr. Hollis himself acknowledged: "The study was small, and results from a larger trial aren’t expected for several years."
2Second, the study did not determine whether vitamin D prevents or cures prostate cancer. Dr. Hollis stated outright: "We don’t know yet whether vitamin D treats or prevents prostate cancer. At the minimum, what it may do is keep lower-grade cancers from going ballistic."
3Third, the study results itself are preliminary. None of Dr. Hollis' new findings have been subject to the rigors of peer review.
Publication in a peer-reviewed medical journal is an important screen where scientists can evaluate the research methods and strength of the evidence, something not done at many scientific meetings.
Why is peer review so important? "Publication in a peer-reviewed medical journal — although no guarantee of integrity or quality — is an important screen," says healthnewsreview.org, a website dedicated to evaluating health news reporting by major U.S. news organizations. "At least other scientists can evaluate and comment on the research methods and on the strength of the evidence, something not done at many scientific meetings."
Why Media Coverage of Scientific Meetings is Too Much, Too Soon
There’s been research about findings reported at scientific meetings, and the results indicate that getting there first isn’t always in our public interest. In the biggest study to date on the topic, "Media Coverage of Scientific Meetings: Too Much, Too Soon?" published in JAMA: Journal of the American Medical Association (June 2002), Dr. Steve Woloshin and Dr. Lisa Schwartz of the Center for the Evaluative Medical Sciences found that 1 out of 4 study findings announced in the media in the aftermath of prominent scientific meetings remained unpublished three years after the initial meeting that heralded the finding.1 out of 4 study findings announced in the media after prominent scientific meetings remained unpublished three years later.
The researchers looked at the abstracts receiving press after five scientific meetings: 12th World AIDS Conferene, American Heart Association, Society for Neuroscience, American Society of Clinical Oncology, and the Radiological Society of North America. A full 25% of the initial abstracts receiving attention were not published, 25% appeared in "low-impact journals," and 50% ran in "high-impact journals" (explanation: these "low" and "high-impact" qualifications were based on Institute for Scientific Information ratings).
It turned out that a noteworthy two thirds of the unpublished abstracts had never even been submitted for publication. The authors said: "[This] may reflect lack of time or concerns about validity."
"Unfortunately, the public does not always benefit from preliminary findings,"Drs. Woloshin and Schwartz explained in "Media Reporting on Research Presented at Scientific Meetings: More Caution Needed," (Medical Journal of Australia, June 2006). "When they turn out not to be true, patients can be hurt by exposure to ineffective or harmful treatments or by forgoing good alternatives."
Other Vitamin D Supplementation-Prostate Cancer Studies Show…
Earlier studies on the benefits of vitamin D supplementation for prostate cancer are decidedly mixed.
Dr. Hollis' previous research (Journal of Clinical Endocrinology and Metabolism, April 2012) showed that for 55% of men with low-grade prostate cancer taking 4,000 IUs of vitamin D for a year, their tumors completely disappeared or showed decreased Gleason scores (indicating the tumor is less likely to spread).
However, again this earlier study’s sample size was too small—52 subjects enrolled, and ultimately only 44 could be analyzed—to be representative of all men with prostate cancer.
More recently, a meta-analysis study of 25 different studies reporting on 17,332 cancer patients (also published in JCEM, April 2014) found that cancer patients who have higher levels of vitamin D when diagnosed tend to have better survival rates and remain in remission longer than those who are vitamin D-deficient (a 10 nmol/L increment in circulating D levels associated with a 4% increase in survival).
Cancer patients who had higher levels of vitamin D when diagnosed tended to have better survival rates, but there is less evidence of this connection in men with prostate cancer.
However, these better patient outcomes occurred more with some types of cancer than others. "Vitamin D may influence the prognosis for people with breast cancer, colorectal cancer and lymphoma, in particular," says study author Hui Wang, MD, PhD, Professor of the Institute for Nutritional Sciences at the Shanghai Institutes for Biological Sciences.
Less evidence of a connection was found in men with prostate cancer.
If You Supplement, Do It Safely
Even researchers studying vitamin D supplementation are cautious about its unregulated use.
Dr. JoAnn E. Manson of the Division of Preventive Medicine at Brigham and Women’s Hospital in Boston, for example, is currently conducting a large-scale (26,000-patient) trial of the role vitamin D may play in cancer, cardiovascular disease, diabetes, depression, infection, autoimmune disorders, and other conditions. She says there are dangers in taking high-level vitamin D. "Go above 4,000 IUs, unless there’s a specific reason that you need that amount, and you risk kidney stones, calcification of blood vessels, and possibly… cardiovascular disease." Dr. Hollis gave prostate cancer patients 4,000 IUs of vitamin D₃ in both of his studies.Vitamin D has adverse interactions with certain medications.The National Institutes of Health — Office of Dietary Supplements offers a different maximum dosage for safe supplementation. NIH says, "Most reports suggest a toxicity threshold for vitamin D of 10,000 to 40,000 IU/day…Symptoms of toxicity are unlikely at daily intakes below 10,000 IU/day…[though the Food and Nutrition Board] pointed to emerging science… that even lower vitamin D intakes… might have adverse health effects over time."
If you do choose to supplement, note that vitamin D has adverse interactions with certain medications, among them Lipitor, various diuretics, and most antacids. Consult MedlinePlus, the National Institutes of Health’s website for patients and families, for more information.
In short, "D" is for "Don't Know Yet."
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