Low vitamin D is a consequence, not a cause, of bladder cancer, according to a recent study published in the journal Clinical Nutrition Open Science.
The biggest known causes of bladder cancer are smoking and exposure to cancer-causing substances at work. Some studies have suggested that low vitamin D might also raise the risk of bladder cancer. To check if this is actually true, researchers compared vitamin D levels in people with bladder cancer and people without bladder cancer.
The study used information from a large health project in northern Sweden called the NSHDS (Northern Sweden Health and Disease Study). The researchers compared 377 people who had bladder cancer with 377 healthy people of the same age, sex, place of residence and time of blood sampling.
They found that people who later got bladder cancer had about the same vitamin D levels as healthy people before they were diagnosed.
“Our results indicate that vitamin D cannot be used as a predictive marker for future bladder cancer,” the researchers said.
Read more about bladder cancer causes and risk factors
They also looked at 353 patients who had blood samples taken at the time of their bladder cancer diagnosis. Out of those, 129 patients had also given blood samples about 13.8 years before their diagnosis. This let the researchers see how vitamin D levels changed over time.
In people who gave blood samples both before and after diagnosis, vitamin D levels were much lower at the time of diagnosis than they were 13.8 years earlier. This suggests the lower vitamin D levels at diagnosis probably happen because of the cancer itself, not the other way around.
“The reduced D vitamin levels in patients with a bladder cancer diagnosis suggest a direct or indirect effect of the malignant disease itself,” the researchers said.
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