New research has suggested that improving people’s blood levels of vitamin D could be an important tool for preventing cancer, after their study found that the risk of developing the disease rises as vitamin D levels fall.
The study was published this week in PLOS One, by researchers from the University of California-San Diego (UCSD) School of Medicine. They have analysed the link between vitamin D and cancer and sought to determine what blood level of vitamin D was required to effectively reduce cancer risk. The study references all types of invasive cancer excluding Skin Cancer.
It is apparently the first study to seek out metrics for the relationship between Cancer and Vitamin D and quantify the amounts of Vitamin D required in the blood.
Cedric Garland, adjunct professor in the UCSD School of Medicine Department of Family Medicine and Public Health, and one of the authors of the paper said:
“We have quantitated the ability of adequate amounts of vitamin D to prevent all types of invasive cancer combined, which had been terra incognita until publication of this paper.”
Vitamin D is produced by the body through exposure to sunshine is important for the control of calcium and phosphate levels. Professor Garland, the originator of this study, was the first person to link low vitamin D with Cancer back in the 1980s, and has gone on to undertake significant amounts more work. Over the years they have found that people who lived at higher latitudes and thus had less access to sunlight had lower levels of vitamin D and were more likely to develop bowel cancer. They have also found links between low vitamin D and other cancers, including cancers of the breast, lung and bladder.
There has been a lot of debate in recent years about what the recommended blood levels of vitamin D should be. In 2010, the Institute of Medicine (IOM) in the USA recommended a target of 20 ng/ml for bone health, which could be met in most healthy adults (aged 19-70), with the equivalent of 600 IU of vitamin D each day. Since then, others have recommended 50ng/ml or more.
Professor Garland’s team wanted to test the amount in this study so they took a different approach to that which is usually used, and drew on metrics for Vitamin D by measuring the level of 25-hydroxyvitamin D in the blood, the only known way to measure it.
They used the results from two different types of study: one a clinical trial of 1,169 women and the other a prospective study of 1,135 women. For some of their analysis, they kept the two data sets separate and compared them, and in another part, they pooled the data to create a larger sample.
The median blood level of 25-hydroxyvitamin D in the participants in the clinical trial was 30 ng/ml, and in the participants in the prospective study, it was 48 ng/ml.
The researchers found that the rate of cancer incidence in the clinical study group (that had the lower median vitamin D level) was higher than in the prospective study group. The figures were 1,020 cases per 100,000 person-years and 722 per 100,000 person-years, respectively.
They also found that cancer rates went down as 25-hydroxyvitamin D levels rose; women whose vitamin D level was 40 ng/ml or higher had a 67% lower risk of developing cancer than women whose vitamin D level was 20 ng/ml or lower.
The published report did not say what the optimum intake level of vitamin D should be – or whether it should be generated by greater exposure to sunlight, or through diet and supplements.
Prof. Garland says their findings simply show that it is possible to see reduced cancer risk when blood levels of vitamin D reach 40 ng/ml, and that higher than this, the risk drops even further. His concluding statement was:
“Primary prevention of cancer, rather than expanding early detection or improving treatment, will be essential to reversing the current upward trend of cancer incidence worldwide. This analysis suggests that improving vitamin D status is a key prevention tool.”