Vitamin D Linked to Enhanced Cancer Immunity through Gut Bacteria, Study Finds

A new study has discovered a significant role for vitamin D in cancer immunity. The findings, published in Science, reveal that vitamin D helps foster a type of gut bacteria known as Bacteroides fragilis, which in turn enhances immune resistance to cancer in mice.

The research, conducted by scientists at the Francis Crick Institute, the National Cancer Institute, and Aalborg University, found that mice fed a vitamin D-rich diet had improved immune responses to cancer, including better outcomes from immunotherapy treatments. This effect was also observed in mice genetically modified to lack a protein that typically hinders vitamin D absorption in tissues.

“What we’ve shown here came as a surprise,” said the study’s lead, Caetano Reis e Sousa, head of the Immunobiology Laboratory at the Crick. Vitamin D can regulate the gut microbiome to favor a type of bacteria that gives mice better immunity to cancer.”

Further experiments demonstrated that administering Bacteroides fragilis to mice on a normal diet resulted in a similar enhancement in tumor resistance, although this was not the case for those on a vitamin D-deficient diet.

The study also explored human data from Denmark, correlating lower vitamin D levels with a higher risk of cancer. According to the researchers, this suggests that vitamin D's influence on gut microbiota could be a critical factor in its ability to modulate immune responses.

Despite these promising results, researchers cautioned that more investigation is necessary to fully understand how vitamin D and gut bacteria interact to boost cancer immunity. However, they explained that their findings could eventually lead to new dietary interventions for cancer prevention and treatment.

“A key question we are currently trying to answer is how exactly vitamin D supports a ‘good’ microbiome," said study author Evangelos Giampazolias, PhD, Group Leader of the Cancer Immunosurveillance Group at the Cancer Research UK Manchester Institute. “If we can answer this, we might uncover new ways in which the microbiome influences the immune system, potentially offering exciting possibilities in preventing or treating cancer.”