Researchers from the Francis Crick Institute, the National Cancer Institute (NCI) of the U.S. National Institutes of Health (NIH), and Aalborg University in Denmark have discovered that vitamin D promotes the growth of a specific type of gut bacteria in mice, enhancing their immunity to cancer.

Published in Science, the study revealed that mice fed a diet high in vitamin D exhibited improved immune resistance to experimentally transplanted cancers and showed enhanced responses to immunotherapy. This effect was replicated when a protein that binds to vitamin D in the blood, keeping it away from tissues, was removed using gene editing.

Surprisingly, the researchers found that vitamin D acts on epithelial cells in the intestine, increasing the abundance of a bacterium called Bacteroides fragilis. This microbe boosted the mice’s immunity to cancer, resulting in slower tumor growth. However, the precise mechanism behind this interaction remains unknown. To assess whether the bacteria alone could confer better cancer immunity, mice on a standard diet were given Bacteroides fragilis. These mice also showed increased resistance to tumor growth, but this effect was not observed when the mice were placed on a vitamin D-deficient diet.

Previous studies have suggested a link between vitamin D deficiency and higher cancer risk in humans, although conclusive evidence has been lacking. To explore this further, the researchers analyzed data from 1.5 million people in Denmark, revealing a correlation between lower vitamin D levels and increased cancer risk. Additionally, an analysis of a population of cancer patients indicated that individuals with higher vitamin D levels were more likely to respond favorably to immune-based cancer treatments. While Bacteroides fragilis is also present in the human microbiome, further research is needed to determine if vitamin D provides similar immune resistance to cancer in humans through the same mechanism.

“What we’ve shown here came as a surprise — vitamin D can regulate the gut microbiome to favour a type of bacteria which gives mice better immunity to cancer. This could one day be important for cancer treatment in humans, but we don’t know how and why vitamin D has this effect via the microbiome. More work is needed before we can conclusively say that correcting a vitamin D deficiency has benefits for cancer prevention or treatment.” – Caetano Reis e Sousa, head of the Immunobiology Laboratory at the Crick and senior author of the study

Dr. Nisharnthi Duggan, Research Information Manager at Cancer Research UK, noted, “A bit of sunlight can help our bodies make vitamin D but you don’t need to sunbathe to boost this process. Most people in the UK can make enough vitamin D by spending short periods of time in the summer sun. We can also get vitamin D from our diet and supplements. We know that staying safe in the sun can reduce the risk of cancer, so make sure to seek shade, cover up and apply sunscreen when the sun is strong.”

Source:

The Francis Crick Institute. “Vitamin D alters mouse gut bacteria to give better cancer immunity.” ScienceDaily. ScienceDaily, 25 April 2024.

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