Researchers from the German Cancer Research Centre say they have uncovered new evidence that daily intake of vitamin D could help reduce the cancer death risk by 12% – and additionally, that there’s more benefit for over 70s taking daily vitamin D than there is for younger people.
The benefits were also greater in people who started taking daily vitamin D preventatively before ever receiving a cancer diagnosis, they said.
About 10m people worldwide die every year from cancer, reports Medical News Today, so scientists are constantly looking for new ways to extend the life expectancy of those with cancer.
The study was published in the journal Ageing Research Reviews.
Vitamin D and cancer risk
This is not the first study to look for a correlation between vitamin D and cancer: previous teams have also scrutinised the vitamin as a preventive measure for specific cancers, like breast and liver cancer.
However, the results have been mixed. For example, one review reported that vitamin D supplementation in adults with healthy vitamin D levels did not prevent cancer or provide other demonstrable health benefits.
Epidemiologist Dr Ben Schöttker, research group leader in the Division of Clinical Epidemiology and Ageing Research at the German Cancer Research Centre and senior author of this study, said they decided to examine the impact of the vitamin on cancer mortality because of evidence from previous trials that cancer mortality is one of the outcomes likely to show a response to vitamin D supplementation.
For this study they focused specifically on vitamin D3.
“A previous systematic review and meta-analysis showed no effect for vitamin D2 on cancer mortality but an effect of vitamin D3 on cancer mortality,” he told Medical News Today. “One can only speculate on the reasons.”
Taking daily
For this study, researchers analysed data and findings from 14 studies for a total of almost 105 000 participants. Scientists only included studies where participants had been randomly assigned to receive either vitamin D3 or a placebo.
After reviewing all of the data, they found no statistically significant results emerged until after considering the dosage each study participant had received.
When study participants were intermittently given very large vitamin D3 doses, no effect was detected on cancer mortality. However, when participants took vitamin D3 daily, the research team found they reduced their cancer mortality rate by 12%.
Additionally, the findings showed that people 70 and older who took vitamin D3 daily benefited the most from the therapy.
“The older you get, the higher your cancer risk,” said Schöttker “Thus, preventive actions against cancer mortality get more effective the older the patients are. As the cancer risk already starts to increase from 50, I personally would already check patients for potential vitamin D supplementation from that ago onwards, and not only from 70.”
Additionally, the beneficial effect was most evident when vitamin D3 was taken preventatively before a study participant ever received a cancer diagnosis.
“This implies that basically everyone aged 50 and older, including people who have never had cancer, might profit from vitamin D supplementation if they are vitamin D insufficient.
“Doctors cannot know who might develop cancer later. However, in Germany, the risk is very high – 43% for women and 51% for men – and …I would say the lifetime risk of developing cancer at least once is comparable in most other industrialised countries,” Schöttker added.
There were limitations in the included studies, however.
For instance, most did not test vitamin D levels at the start of the trials, so it is unclear how many participants were vitamin D deficient. In addition, while all were allocated to either vitamin D3 or a placebo, most of the trials allowed participants in the placebo group to self-medicate with vitamin D supplements.
Study details
Efficacy of vitamin D3 supplementation on cancer mortality: Systematic review and individual patient data meta-analysis of randomised controlled trials
Sabine Kuznia, Anna Zhu, Taisuke Akutsu, Ben Schöttker, et al.
Published in Ageing Research Reviews in Vol 87 June 2023
Abstract
To evaluate the effect of vitamin D3 supplementation on cancer mortality in the general population and on prognosis in cancer patients, a systematic review and meta-analysis of randomised, placebo-controlled trials (RCTs) and individual patient data (IPD) was conducted. Overall, 14 RCTs with a total of 104,727 participants (2015 cancer deaths) were identified and 7 RCTs, including 90 % of all study participants (n = 94,068), could be included in the IPD meta-analyses. The main meta-analysis of the 14 RCTs yielded a statistically non-significant reduction in cancer mortality by 6 % (risk ratio (RR) [95%-confidence interval (95%CI)]: 0.94 [0.86–1.02]). Subgroup analyses revealed a 12 % lower cancer mortality in the vitamin D3 group compared with the placebo group in 10 trials with a daily dosing regimen (RR [95%CI]: 0.88 [0.78–0.98]), whereas no mortality reduction was seen in 4 trials using a bolus regimen (RR [95%CI]: 1.07 [0.91–1.24]; p-value for interaction: 0.042). The IPD meta-analysis (RR [95%CI]: 0.93 [0.84; 1.02]) confirmed the finding of all trials. The IPD were used to test effect modification by age, sex, body mass index, ethnicity, baseline serum 25-hydroxyvitamin D concentration, adherence and cancer-related factors but no statistically significant findings were obtained in meta-analyses of all trials. When restricted to trials with daily dosing in a post-hoc analysis, adults aged ≥ 70 years (RR [95%CI]: 0.83 [0.77; 0.98]) and subjects with vitamin D3 therapy initiation before cancer diagnosis (RR [95%CI]: 0.87 [0.69; 0.99]) appeared to benefit most from daily vitamin D3 supplementation. Measurements of baseline 25-hydroxyvitamin D levels and inclusion of other than non-Hispanic white adults were too sparse in the trials to draw conclusions. Results for all-cause and cancer-specific survival of participants with cancer were comparable to those obtained in the general population for cancer mortality. In conclusion, vitamin D3 did not reduce cancer mortality in the main meta-analysis of all RCTs because the observed risk reduction by 6 % was not statistically significant. However, a subgroup analysis revealed that vitamin D3 administered daily, in contrast to bolus supplementation, reduced cancer mortality by 12 %.
Medical News Today article – Taking vitamin D daily may reduce cancer mortality by 12% (Open access)
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