Residents of Japan with higher concentrations of vitamin D were less likely to develop cancer than those with lower levels, according to a cohort study recently published in The BMJ.
“While the benefits of vitamin D on bone diseases are well known, there is growing evidence that vitamin D may benefit other chronic diseases, including some cancers. But so far, most studies have been carried out in European or American populations, and evidence from Asian populations is limited,” Taiki Yamaji, MD, of the Center for Public Health Sciences, National Cancer Center in Tokyo, told Healio Family Medicine.
Researchers assessed the link between prediagnostic circulating vitamin D concentration and the subsequent risk for overall and site-specific cancer in 3,301 incident cases of cancer and 4,044 randomly selected subcohort participants across nine public health centers in Japan. Participants were split into quarters based on their sex and season of year vitamin D levels were assessed; the first quarter had the lowest vitamin D levels and the fourth quarter had the highest.
Yamaji and colleagues found that the plasma concentration level was inversely linked to the risk for total cancer, for quarter two, (adjusted HR = 0.81; 95% CI, 0.7-0.94) quarter three (aHR = 0.75; 95% CI, 0.65-0.87) and quarter four (aHR = 0.78; 95% CI, 0.67-0.91) compared with the first quarter. There was also an inverse link for liver cancer (Second quarter aHR = 0.7 [95% CI, 0.44–1.13]; third quarter aHR = 0.65 [95% CI, 0.4–1.06]; and fourth quarter aHR = 0.45 [95% CI, 0.26–0.79]).
Researchers also found that a sensitivity analysis showed alternately removing cases of cancer at a specific site from total cancer cases did not cause a substantial change in overall hazard ratios. In addition, the levels of vitamin D were generally higher in those participants tested during from June through November, and lower in those tested December through May.
“Our findings suggest that vitamin D may exert a biologically protective effect against cancers at many site,” Yamaju said in the interview. “Given that many tissues in the body express 1-hydroxylase, which produces the active form of vitamin D, namely 1,25-dihydroxyvitamin D, and that an even wider range of tissues possess receptors for 1,25-dihydroxyvitamin D, the anticarcinogenic effect of vitamin D is probably not limited to a single organ or tissue in the body.”
“Further studies are needed to clarify the optimal concentrations of vitamin D for cancer prevention,” he added.
The Vitamin D Council states on its website that maintaining a serum level of 125 nmol/L is recommended, but also says the medical community is divided over what are considered deficient, sufficient or toxic vitamin D levels. – by Janel Miller
Vitamin D Council. “Position statement on supplementation, blood levels and sun exposure.” https://www.vitamindcouncil.org/for-health-professionals-position-statement-on-supplementation-blood-levels-and-sun-exposure/. Accessed April 16, 2018.
The authors report no relevant financial disclosures.