Vitamin D "substantially reduces all-cancer risk" - by 60%!

I've blogged before about the health importance of vitamin D, the sunshine vitamin, and new evidence keeps coming out. In June of this year the results of a great vitamin D study were published that concluded that "Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women.^" The study is very high quality because it was a "4-y, population-based, double-blind, randomized placebo-controlled trial" with 1179 post menopausal women. The first key point is that the subjects that took vitamin D plus calcium had 60% less cancer (compared to those that took the placebo) over all 4 years (with a P value of 0.01, meaning the probability that this result was due to chance alone is 1%), and 80% less cancer "when the analysis was confined to cancers diagnosed after the first 12 mo" (with a P value of less than 0.005 indicating even higher confidence). The second key point is that because the trial was an intervention trial (double-blind, randomized placebo-controlled) it shows that vitamin D (possibly plus calcium) was actually the cause of this reduction in cancer (as opposed to just being correlated with it, as most previous studies have shown). And by the way, a third group that was given just calcium did have reduced cancer rates too but the reduction in cancer was not as significant and the results were not as conclusive (due to a higher P value). I wish the study had had a fourth group that took just vitamin D - I bet this would have shown that vitamin D alone prevents cancer significantly.

If you want to read something less technical than the actual study then I recommend an article at theglobeandmail.com that describes the study like this: "A four-year clinical trial involving 1,200 women found those taking the vitamin had about a 60-per-cent reduction in cancer incidence, compared with those who didn't take it, a drop so large — twice the impact on cancer attributed to smoking — it almost looks like a typographical error." It's also got a bunch of great background on vitamin D and the increasing awareness of it in the medical industry as something of a wonder drug that prevents diseases of all kinds.

Another recent study suggests that vitamin D is likely safe up to at least 40,000 IU per day, and remember that it is extremely cheap (~$10 for a years supply), so take more vitamin D! I've been taking over 4000 IU per day for at least 6 months, and my dad is up to 7500 IU per day now :)