Heidelberg – Vitamin D intake could reduce cancer mortality in the population by twelve percent – provided the vitamin is taken daily. This was the result of an evaluation of 14 studies of the highest quality level with a total of almost 105,000 participants carried out at the German Cancer Research Center.
Vitamin D deficiency is widespread worldwide and is particularly common in cancer patients. Averaged over the year, the vitamin D blood levels in around 15 percent of German adults are below the threshold for a pronounced vitamin D deficiency*. In contrast, in a study of colorectal cancer patients, researchers diagnosed vitamin D3 deficiency in 59 percent of the participants, which was also associated with an unfavorable prognosis.
Possible effects of vitamin D supplementation and the development or prognosis of cancer have already been examined in numerous studies. “According to the current study situation, vitamin D3 intake probably does not protect against developing cancer, but it could reduce the probability of dying from cancer. However, previous studies on cancer mortality have delivered very different results and we are interested in the reasons for this”, says Ben Schöttker, epidemiologist at the German Cancer Research Center. “By re-evaluating all previous studies on the subject, we wanted to contribute to arriving at reliable results on this issue, which is so relevant to public health.”
In order to investigate the effectiveness of vitamin D3 on cancer mortality in the population and on the survival of cancer patients, Ben Schöttker and colleagues carried out a systematic literature search in which 14 studies with a total of almost 105,000 participants were identified. The researchers only considered studies of the highest quality, whose participants had been randomly assigned to the vitamin D3 arm or the placebo arm.
No statistically significant results were found in the summary of all 14 studies. However, if the studies were divided according to whether daily vitamin D3 intake was low** or as an infrequently administered, high single dose**, there was a big difference. In the four studies with the high single doses, there was no effect on cancer mortality. In the summary of the ten studies with daily dosing, however, the researchers determined a statistically significant reduction in cancer mortality of twelve percent.
“We observed this 12 percent reduction in cancer mortality after untargeted vitamin D3 administration to people with and without vitamin D deficiency. We can therefore assume that the effect for people who actually have a vitamin D deficiency is significant is higher,” says Ben Schöttker. He explains the better effectiveness of the daily vitamin D3 doses by the more regular bioavailability of the active ingredient, the hormone 1,25-dihydroxyvitamin D, which is only produced by reactions of the vitamin D in the body and can presumably inhibit tumor growth.
A more detailed analysis of the studies with daily intake also found that people aged 70 and over benefited the most from vitamin D3 therapy. In addition, the effect was most evident when vitamin D intake was started before the cancer was diagnosed.
Hermann Brenner, epidemiologist and prevention expert at the DKFZ, adds: “This work underlines the great potential of vitamin D3 administration in the prevention of cancer deaths. Regular intake in low doses** is associated with almost negligible risk and very low cost.”
The current work was funded by the German Cancer Aid.
publication
Kuznia S, Zhu A, Akutsu T, Buring JE, Camargo CA Jr, Cook NR, Chen LJ, Cheng TD, Hantunen S, Lee IM, Manson JE, Neale RE, Scragg R, Shadyab AH, Sha S, Sluyter J, Tuomainen TP, Urashima M, Virtanen JK, Voutilainen A, Wactawski-Wende J, Waterhouse M, Brenner H, Schöttker B. Efficacy of vitamin D3 supplementation on cancer mortality: Systematic review and individual patient data meta-analysis of randomised controlled trials. Ageing Res Rev. 2023, DOI: 10.1016/j.arr.2023.101923.
* The threshold value of the 25-hydroxyvitamin D level in the blood used for vitamin D deficiency was 30 nmol/L (= 12 ng/ml). If one includes people with a less serious vitamin D deficiency (25-hydroxyvitamin D level in the blood < 50 nmol/L (= 20 ng/ml)), slightly more than half of Germans have at least a deficiency. However, there are guidelines that use other thresholds. Since the vitamin D level in the blood mainly depends on the tanning of the skin, this percentage also fluctuates greatly with the seasons.
** The studies used low daily doses of 400 to 4000 IU per day and single high doses of 60,000 to 120,000 IU once a month or less.
With more than 3,000 employees, the German Cancer Research Center (DKFZ) is the largest biomedical research facility in Germany. More than 1,300 scientists at the DKFZ research how cancer develops, record cancer risk factors and search for new strategies to prevent people from developing cancer. They are developing new methods with which tumors can be diagnosed more precisely and cancer patients can be treated more successfully. At the Cancer Information Service (KID) of the DKFZ, those affected, interested citizens and specialist groups receive individual answers to all questions on the subject of cancer. Together with partners from the university clinics, the DKFZ operates the National Center for Tumor Diseases (NCT) at the Heidelberg and Dresden sites, and the Hopp Children’s Cancer Center KiTZ in Heidelberg. In the German Consortium for Translational Cancer Research (DKTK), one of the six German Centers for Health Research, the DKFZ maintains translation centers at seven university partner locations. The combination of excellent university medicine with the top-class research of a Helmholtz center at the NCT and DKTK locations is an important contribution to transferring promising approaches from cancer research to the clinic and thus improving the chances of cancer patients. The DKFZ is funded 90 percent by the Federal Ministry of Education and Research and 10 percent by the state of Baden-Württemberg and is a member of the Helmholtz Association of German Research Centers.