Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial.

This is Fig. 2 from the study in the title.

FIGURE 2.

Kaplan-Meier survival curves (ie, free of cancer) for the 3 treatment groups randomly assigned in the cohort of women who were free of cancer at 1 y of intervention (n = 1085). Sample sizes are 266 for the placebo group, 416 for the calcium-only (Ca-only) group, and 403 for the calcium plus vitamin D (Ca + D) group. The survival at the end of study for the Ca + D group is significantly higher than that for the placebo group, by logistic regression. (Copyright Robert P Heaney, 2006. Used with permission.)

The reason why I'm making this post is because I was accused (on Twitter) of being a danger to women who had breast cancer and I was added to a Quackery list. I was alleged to have claimed that taking Vitamin D reduces the risk of getting cancer in the first place and/or of getting recurring cancer.

Obviously, I wasn't happy about this! I do not recall ever having made such a claim. If I have, please point it out and I will make a full retraction and apology. The study in question is Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial.

Please note: Ignoring cancer diagnoses within the first 12 months removes results from women who had undiagnosed cancer at the start of the study.

What the study shows:

Taking 1,100iu/day of Vitamin D3 + 1,400-1,500mg/day of Calcium: When analyzed by intention to treat, cancer incidence was lower in the Ca + D women than in the placebo control subjects (P < 0.03). When analysis was confined to cancers diagnosed after the first 12 mo, RR for the Ca + D group fell to 0.232 (CI: 0.09, 0.60; P < 0.005). 0.232 is a reduction of 77%.

What the study doesn't show:

Taking Vitamin D3 only reduces the RR for cancer incidence. I believe that it probably does.
Taking Ca + D reduces the RR for cancer recurrence. I believe that it probably does.
Taking more than 1,100iu/day of Vitamin D3 reduces cancer incidence more. I believe that it probably does.
Taking Ca + D reduces the RR for cancer incidence in pre-menopausal women. I believe that it probably does.
Taking Ca + D reduces the RR for cancer incidence in men. I believe that it probably does.
Taking Ca + D increases the RR for breast cancer mortality. I believe that the opposite is the case.
Anything other than what the study shows.

See also Is Vitamin D Shooting Me in the Foot?