Research team determines level of vitamin D needed to prevent cancer

VitaminDBenefitsOn February 29 we reported on new research that demonstrated vitamin D supplements lowered the risk of heart disease.

Now researchers from the University of California-San Diego (UCSD) School of Medicine are reporting on how they analyzed the link between vitamin D and cancer to determine what blood level of vitamin D was required to effectively reduce cancer risk.

The study included all invasive cancers, excluding skin cancer.

One of the authors, Cedric Garland, adjunct professor in the UCSD School of Medicine Department of Family Medicine and Public Health, says their study is the first to put numbers on this relationship, as he explains:

“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, which is produced by the body through exposure to sunshine, helps the body control calcium and phosphate levels—amongst numerous other biological functions.

Garland, along with his late brother Frank Garland, were the first researchers to link low vitamin D with cancer in the 1980s. They found 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.

Since then, further studies by the Garland brothers and others have found links between low vitamin D and other cancers, including cancers of the breast, lung and bladder.

It stands to reason that, after the vitamin D – cancer link was clearly  established, that experts started to debate what the recommended blood levels of vitamin D should be. In 2010, the Institute of Medicine (IOM) 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, other groups have argued that the target level should be higher, at 50 ng/ml or more.

In the new study, Prof. Garland and colleagues wanted to find out what blood level of vitamin D effectively reduces cancer risk.

They took an approach that is not normally used. 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.

It turns out, according to their research, that vitamin D levels of 40 ng/ml or higher were linked to a 67% lower cancer risk.

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 researchers themselves did not say what the optimum intake level of vitamin D should be based on their research. Their goal was to simply report the results.

The researchers also leave the method of generating vitamin D up to the individual.  This can be accomplished by greater exposure to sunlight, changes in diet, or with nutritional supplements.

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.

Their published results summarize it this way:

“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.”