Low vitamin D levels linked to a higher risk of bladder cancer and other cancers

Every cell in the body depends on vitamin D, which regulates approximately 10 percent of our genes and plays a vital role in overall health. According to a comprehensive review published in Cancer Medicine, low blood levels of vitamin D are associated with an increased risk of bladder cancer and several other forms of cancer. The authors describe a number of biological mechanisms through which vitamin D may help protect against cancer development.

Bladder cancer is characterized by a high rate of recurrence, and many patients experience a return of the disease after treatment. Because bladder cancer is associated with significant mortality, optimizing vitamin D status may have considerable potential - not only for prevention but also as a supportive component of cancer treatment.
Cancer of the bladder is among the most common cancers worldwide, and approximately 70 percent of patients experience recurrence after treatment. In 2020 alone, an estimated 573,000 new cases and 212,000 deaths were reported globally, highlighting the substantial human and economic burden of the disease.
This particular cancer form is most prevalent in Europe and North America, and men are affected more frequently than women. In addition to genetic susceptibility, risk factors include smoking, excessive alcohol consumption, exposure to environmental toxins, obesity, and physical inactivity.
Researchers have also focused increasingly on the role of nutrition, and it is estimated that as many as one-third of cancer cases may be preventable through dietary and lifestyle measures, including adequate intake of key nutrients. Because vitamin D deficiency is widespread and vitamin D is known to possess several cancer-protective properties, the researchers behind the new umbrella review investigated the relationship between vitamin D status and bladder cancer risk.
The researchers also evaluated participants' intake of vitamin D from food sources (which typically deliver modest amounts only) as well as from dietary supplements.
Using multiple scientific databases, the investigators identified a number of previously published studies and meta-analyses. Eight studies met the inclusion criteria for the umbrella review. Blood vitamin D levels below 30 nmol/L were classified as critically low.
The analysis revealed that critically low vitamin D status was associated with an increased risk of bladder cancer, whereas levels above 30 nmol/L appeared to offer some degree of protection. It should be noted, however, that many experts recommend maintaining blood vitamin D levels above 75 nmol/L to support optimal health.
When it came to vitamin D intake from food and supplements, the findings were less clear. One reason may be that sunlight exposure plays a crucial role in determining vitamin D levels in the bloodstream. Other studies have also shown that magnesium is required for converting vitamin D obtained from sunlight or supplements into its circulating form and subsequently into the active steroid hormone form used by cells throughout the body.
As a result, individuals may respond quite differently to vitamin D obtained from sunlight, food, and supplements.

How vitamin D may help protect against bladder cancer

In their introduction, the authors describe several mechanisms through which vitamin D may help prevent or slow the progression of bladder cancer:

• Direct anti-tumor activity
  The active form of vitamin D may directly inhibit the growth of cancer cells and promote programmed cell death (apoptosis), helping to limit tumor development and spread.
• Enhanced immune function
  Vitamin D supports the immune system, which plays a critical role in identifying and eliminating abnormal cells, including cancer cells.
• Regulation of inflammation and oxidative stress
  Vitamin D also helps regulate inflammatory processes and oxidative stress, both of which are commonly involved in the development and progression of cancer.
• Improved response to BCG immunotherapy (Bacillus Calmette-Guérin)
  The BCG vaccine, originally developed for tuberculosis prevention, is widely used as an immunotherapy treatment for bladder cancer. Vitamin D may enhance the effectiveness of this thera
• Increased sensitivity to chemotherapy
  Research suggests that vitamin D may increase the responsiveness of cancer cells to chemotherapy agents such as cisplatin and gemcitabine, potentially helping to reduce treatment resistance.

Additional evidence for vitamin D's role in cancer prevention

Over the past several decades, extensive research has explored vitamin D's role in both cancer prevention and cancer treatment. In the following article, you can learn more about why optimal health benefits and cancer-protective effects may require blood vitamin D levels above 75 nmol/L.
This also raises questions about whether current official reference ranges for vitamin D are set too low. As mentioned earlier, adequate magnesium intake is equally important, since vitamin D must be activated before it can perform its many functions in the body.

• Vitamin D's optimal effect on health and lifespan requires higher blood levels of the nutrient

References:

Stefano Mancin et al. Vitamin D and Bladder Cancer Risk: An Umbrella Review and Second Order Meta-analysis. Cancer Medicine. 2026

Korin Miller. Scientist Find Taking Magnesium Alongside Vitamin D Has Surprising Side Effect. Prevention 2026.