Vitamin D is very important to overall health, yet despite the importance vitamin D deficiency is rather common globally, and is especially prevalent among cancer patients. For example, it is estimated that in Germany alone around 15% of the adult population is vitamin D deficient. A study involving colorectal cancer patients found this deficiency among 59% of its patients, and D3 deficiency was associated with an unfavorable cancer prognosis.
“Based on current studies, vitamin D3 supplementation probably does not protect against developing cancer, but it could reduce the likelihood of dying from cancer. However, previous studies on cancer mortality have yielded very different results, and we were interested in the reasons for this,” says Ben Schöttker, an epidemiologist at the German Cancer Research Center. “By re-evaluating all previous studies on the topic, we wanted to help produce robust results on this issue, which is so relevant to population health.”
To investigate the effectiveness of vitamin D3 on cancer mortality rate across the population and the survival rates of cancer patients, the researchers searched systematic literature to identify 14 studies, including only those that were considered to be of the highest quality in which participants were randomly assigned vitamin D3 or a placebo.
When the data was pooled together no statistically significant result emerged, but when the studies were divided according to either high (60,000 to 120,000 IU once per month or less) or low (400 to 4000 IU per day) daily doses a difference became apparent. Across 4 studies with infrequent higher doses there did not appear to be an effect on cancer mortality, but among 10 studies featuring daily doses a significant 12% decrease in cancer mortality was found. It was noted that those aged 70+ benefited most from vitamin D3 therapy and that the effect was most prominent when intake was started before cancer diagnosis.
“We observed this twelve percent reduction in cancer mortality after un-targeted vitamin D3 administration to individuals with and without vitamin D deficiency. We can therefore assume that the effect is significantly higher for those people who are actually vitamin D deficient,” Schöttker reports.
The researchers believe that better efficacy of daily dosing may be the result of the more regular bioavailability of the active ingredient, hormone 1,25-dihydroxy vitamin D which is only produced in the body and may be able to presumably inhibit tumor growth.
“This work underlines the great potential of vitamin D3 administration in the prevention of cancer deaths. Regular intake at low doses is associated with almost negligible risk and very low cost,” concludes Hermann Brenner, epidemiologist and prevention expert at DCRC.
