There’s an old adage in medicine: an ounce of prevention is worth a pound of cure. I couldn’t agree more. The problem with a lot of truly preventive medicine is this: there’s not much money in it. The real money (for, say, drug companies) is in treatment. To an extent there can be money too in diagnosis (e.g. mammography and blood tests for prostate cancer).
It is a sad fact of life that the medical approaches that get most attention tend to be those that are most lucrative. When things are cheap, there often is not the commercial will and push that can be instrumental in their popularisation.
One approach which shows considerable promise as a disease-preventer is optimisation of vitamin D levels. Heightened levels of vitamin D are associated with reduced risk of a range of chronic diseases including heart disease, diabetes and several forms of cancer. Only this week, saw the publication of a study which links supplementation with vitamin D (at a dose of 400 IU or more a day) with a 26 per cent reduced risk of breast cancer . This study study is epidemiological in nature, and therefore cannot be used to conclude that vitamin D supplementation reduces breast cancer (all we know from this study is that vitamin D supplementation is associated with lower breast cancer risk).
However, this is not the only research linking vitamin D with reduced breast cancer risk. In one 2005 meta-analysis (grouping of relevant studies)  nine of 13 studies found higher levels of vitamin D to be associated with a reduced risk of breast cancer incidence or death due to breast cancer. This meta-analysis also found evidence for higher levels of vitamin D and reduced risk of prostate and colon cancer too. This review also details a range of mechanisms through which vitamin D might reduce cancer risk. For access to the free full text version of this review, click here.
So, what we appear to have a significant volume of research which links vitamin D with a reduced risk of cancer, as well as a number of plausible mechanisms which could explain this association.
However, what we require to confirm (or otherwise) the notion that vitamin D protects against cancer are controlled clinical trials. One study that has relevance here was published in 2007. In it, post-menopausal women were treated with either vitamin D (1100 IU per day) and calcium (1400-1500 mg per day), or calcium alone, or placebo. The trial lasted for four years. Supplementation would not be expected to reduce cancer incidence very quickly, so the authors of this study separately analysed data from one year into the study and beyond.
This analysis revealed that compared to placebo, calcium supplementation alone did not reduce risk of cancer. However, calcium coupled with vitamin D did. Risk of cancer was reduced by 77 per cent.
Ideally, it would be nice to have the results of randomised controlled studies which used vitamin D alone (compared to placebo). However, even in the absence of such studies, it seems clear that we have a considerable and mounting body of evidence that suggests that vitamin D has considerable potential to prevent cancer. I am also pleased to see that there is growing recognition of this, despite the fact that vitamin D has relatively limited potential from a commercial perspective.
1. Anderson LN, et al. Vitamin D and calcium intakes and breast cancer risk in pre- and postmenopausal women. Am J Clin Nutr 14th April 2010 [epub ahead print].
2. Garland CF, et al. The role of vitamin D in cancer prevention. Am J Public Health 2006; 96: 252-61.
3. Lappe JM, et al. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr 2007; 85(6):1586-1591
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