My hope is that the findings from this research might shape healthcare guidelines by identifying vitamin D status as a key prevention tool. Being aware of the relationship of cancer and low vitamin D would allow primary prevention to slow or reverse upward trends in cancer incidence, treatment burden, mortality, and associated costs.
Look at 2012. There were 14 million new cases of cancer worldwide in 2012 and 8.2 million cancer- related deaths. The annual number of new cases is projected to increase to 22 million within the next twenty years.
In Europe and North America cancer is the most significant cause of death and morbidity after cardiovascular diseases.
In this study, University of California, San Diego School of Medicine researchers sought to determine what blood level of vitamin D was required to effectively reduce cancer risk. They were specifically looking at 25-hydroxyvitamin D, the main form of vitamin D in the blood, as a marker for vitamin D levels. They combined data from two previous studies. One was a randomized clinical trial of 1,169 women (Lappe trial cohort) and the other was a prospective cohort study of 1,135 women (GrassrootsHealth cohort). By combining the two studies, the researchers were able to work from a larger sample size and a greater range of blood serum levels of 25-hydroxyvitamin D (25(OH)D).
It is generally accepted that the most accurate measure of vitamin D levels in a person is a blood test. In the Lappe trial cohort, the median blood serum level of 25(OH)D was 30 nanograms (ng) per millilitre (ml). In the GrassrootsHealth prospective cohort, it was higher: 48 ng/ml. The team found that the age-adjusted cancer incidence was 1,020 cases per 100,000 person-years in the Lappe cohort and 722 per 100,000 person-years in the GrassrootsHealth cohort.
In other words, rates of cancer declined with increased 25(OH)D levels. Females with 25(OH)D concentrations of 40 ng/ml or greater had a 67% lower risk of cancer than women with levels of 20 ng/ml or less.
"These findings support an inverse association between 25(OH)D and risk of cancer," said Dr Cedric Garland, adjunct professor in the UC San Diego School of Medicine Department of Family Medicine and Public Health and member of Moores Cancer Center at UC San Diego Health.
“It highlights the importance for cancer prevention of achieving a vitamin D blood serum
The results suggest the importance of vitamin D for the prevention of cancer and are supported by a number of additional studies that have also found a similar reduction in risk for individual cancers.
In a hospital-based case control study women with serum concentrations of more than 60 ng/ml had an 83% reduction in breast cancer risk compared to women with concentrations less than 20 ng/ml.
A population based study found a 63% lower risk of breast cancer for women with 25(OH)D concentrations of 30 ng/ml compared to women with concentrations of less than 20 ng/ml, with a 71% lower risk among post-menopausal women.
A nested case control study found a 55% lower risk of colorectal cancer in women with 25(OH)D concentrations of 29 ng/ml compared to women with concentrations of less than 18 ng/ml.
The wealth of studies has made recommending an optimum blood serum level of vitamin D difficult to establish.
Garland did not identify a singular, optimum daily intake of vitamin D or the manner of intake, which may be sunlight exposure, diet and/or supplementation.
He stated that the current study clarified that reduced cancer risk became measurable at 40 ng/ml, with additional benefit at higher levels.
All of this means that a target vitamin D level recommended by the US Institute of Medicine of 20g/mL is not ideal for reducing cancer risk. If that is the goal higher blood levels may be advised.
Authors: Sharon McDonnell, Carole Baggerly, Christine French, Leo Baggerly, Cedric Garland, Edward Gorham, Joan Lappe, Robert Heaney.