Previous research found that 55% of low-grade prostate cancer patients who took vitamin D supplements for a year demonstrated decreased Gleason scores.
Within the Gleason Grading System used by pathologists, tumors with a Gleason score of 7 or above are considered to be aggressive. These tumors are likely to spread, so tumors affecting the prostate will require the prostate gland to be surgically removed.
However, prostate tumors that have a Gleason score of 6 or below are less aggressive and may not even cause symptoms or health problems for the duration of the patient's life. Despite this, some men with these tumors do decide to have an elective prostatectomy.
If a patient does decide to undergo prostatectomy to remove their low-grade tumor, they must wait 60 days from the time of biopsy before the procedure can be undertaken. This waiting period is to allow the inflammation caused by the biopsy to subside.
The researchers behind the new study, from the Medical University of South Carolina in Charleston, wanted to investigate whether vitamin D supplements would have any benefit for the patient during this 60-day waiting period.
Previous research by the team had found that 55% of men with low-grade prostate cancer who took vitamin D supplements for a year demonstrated decreased Gleason scores, with some tumors even disappearing completely.
Preliminary findings from small randomized controlled trial
For the new study, the team enrolled 37 men awaiting elective prostatectomies into a randomized controlled trial where one group received vitamin D supplements each day and the other received placebos.
According to the preliminary results from the trial, many of the men who received the supplements demonstrated improved outcomes. However, the men who received a placebo either had no change to their tumors or their tumors got worse.
The researchers found dramatic changes in the levels of lipids and proteins involved in inflammation among the participants who received the vitamin D. "Cancer is associated with inflammation, especially in the prostate gland," says researcher Bruce Hollis. "Vitamin D is really fighting this inflammation within the gland."
In particular, a protein called growth differentiation factor 15 (GDF15) was strongly induced by the vitamin D. GDF15 has been found by previous studies to "dial down" inflammation and scientists know that aggressive prostate cancers make very little of this protein.
The preliminary findings, therefore, imply that the mechanism driving the association between Gleason score improvements and vitamin D is a reduction in inflammation conferred by the supplements.
"We don't know yet whether vitamin D treats or prevents prostate cancer," cautions Hollis. "At the minimum, what it may do is keep lower-grade prostate cancers from going ballistic."
The participants in the study received levels of vitamin D in their supplements that were well below the equivalents of vitamin D produced within the human body from daily sun exposure. As Hollis says:
"We're treating these guys with normal body levels of vitamin D. We haven't even moved into the pharmacological levels yet."
Recently on Medical News Today, we looked at a study published in JAMA Internal Medicine that found vitamin D supplementation is ineffective for lowering blood pressure. The findings are significant as many clinicians recommend that patients with hypertension should take vitamin D.