Vitamin D impacts gut health and improves cancer immunity, study finds

Researchers have uncovered a surprising connection between vitamin D, gut bacteria, and cancer immunity in mice. This study, published in Science, offers a novel perspective on how dietary and microbial factors might influence our body's ability to fight cancer.

The team, led by scientists from the Francis Crick Institute, the National Cancer Institute (NCI), and Aalborg University, observed that mice fed a vitamin D-rich diet exhibited enhanced resistance to transplanted tumors.

This improved immunity also translated to a better response to immunotherapy, a promising cancer treatment that harnesses the body's own immune system.

Interestingly, the effect persisted even when the researchers used gene editing to remove a protein that normally binds vitamin D in the bloodstream, limiting its availability to tissues.

Further investigation revealed an unexpected twist. Vitamin D appeared to be exerting its influence not directly on immune cells, but rather on epithelial cells lining the intestines. These intestinal cells, in turn, promoted the growth of a specific type of bacteria called Bacteroides fragilis.

When mice were given Bacteroides fragilis supplements alone, they too displayed improved tumor resistance, highlighting the bacterium's role in boosting immunity. However, this effect was abolished when the mice were placed on a vitamin D-deficient diet.

These findings align with previous human studies suggesting a link between vitamin D deficiency and an increased risk of cancer. The researchers delved deeper, analyzing data from 1.5 million people in Denmark.

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The analysis supported the association between lower vitamin D levels and a higher risk of cancer. Additionally, a separate analysis of cancer patients revealed that those with higher vitamin D levels were more likely to respond positively to immune-based cancer treatments.

While Bacteroides fragilis is also present in the human gut microbiome, further research is necessary to determine whether vitamin D fosters cancer immunity in humans through the same mechanism observed in mice.

"This is a surprising discovery," remarks Caetano Reis e Sousa, senior author and head of the Immunobiology Laboratory at the Crick Institute. "Vitamin D appears to regulate the gut microbiome, favoring a specific bacterial species that enhances cancer immunity in mice." He emphasizes the need for further investigation before definitively linking vitamin D supplementation to cancer prevention or treatment in humans.

Evangelos Giampazolias, now leading the Cancer Immunosurveillance Group at the Cancer Research UK Manchester Institute, highlights the challenge of distinguishing "good" from "bad" gut bacteria. He emphasizes the study's finding that vitamin D supports gut bacteria in eliciting cancer immunity and improving immunotherapy response in mice.

"Unraveling the precise mechanisms by which vitamin D fosters a beneficial microbiome is crucial," he states. "This knowledge could unlock new avenues for exploiting the microbiome's influence on the immune system, potentially leading to exciting possibilities in cancer prevention and treatment."

Romina Goldszmid, an investigator at the NCI's Center for Cancer Research, underscores the contribution of this research to the growing understanding of the gut microbiome's role in cancer immunity.

She emphasizes the potential of dietary interventions to modulate this relationship for improved patient outcomes. However, she acknowledges the need for further research to elucidate the underlying mechanisms and translate them into personalized treatment strategies.

This study, funded by multiple prestigious organizations, represents an early but significant step towards understanding the complex interplay between vitamin D, gut bacteria, and the immune system's response to cancer.

While the findings suggest a promising link, further research is warranted to confirm its applicability to humans and explore the potential for dietary or microbial interventions in cancer prevention and treatment.

Dr. Nisharnthi Duggan, Research Information Manager at Cancer Research UK, reminds us that vitamin D deficiency can be detrimental to health, but the evidence linking vitamin D levels to cancer risk remains inconclusive. This study, while promising, requires further validation.

She emphasizes that moderate sun exposure can boost vitamin D production, but sunbathing is not recommended. Most individuals can obtain sufficient vitamin D through limited summer sun exposure, dietary sources, and supplements. However, sun safety remains paramount – seeking shade, covering up, and applying sunscreen are crucial when UV radiation is intense.

This research paves the way for exciting future investigations into the intricate relationship between vitamin D, the gut microbiome, and cancer immunity. Unlocking these secrets holds the potential to revolutionize our approach to cancer prevention and treatment, potentially empowering us to harness the power of our own bodies for a healthier future.

Fatty Fish: Salmon, mackerel, trout, and tuna are excellent sources of vitamin D. They're not only delicious but also packed with omega-3 fatty acids and protein.

Egg Yolks: Eggs, especially the yolks, are rich in vitamin D. Opt for free-range or pasture-raised eggs for even more nutrients.

Mushrooms: Some varieties of mushrooms, like shiitake and portobello, contain vitamin D, particularly when exposed to sunlight during growth.

Fortified Foods: Many foods are fortified with vitamin D, such as fortified dairy products (milk, yogurt, cheese), plant-based milk alternatives (soy, almond, oat), orange juice, and breakfast cereals.

Cod Liver Oil: A teaspoon of cod liver oil provides a significant amount of vitamin D, along with omega-3 fatty acids and vitamin A.

Fortified Tofu: Tofu is often fortified with various nutrients, including vitamin D. Check the label to ensure it's fortified.

Fortified Cereals: Certain breakfast cereals are fortified with vitamin D, making them a convenient option for boosting your intake.

Fortified Beverages: Besides milk and orange juice, some other beverages like certain types of almond or soy milk are fortified with vitamin D.

Sunlight-Exposed Mushrooms: Exposing mushrooms to sunlight for a period before consumption can increase their vitamin D content.

When incorporating these foods into your diet, remember to consider portion sizes and overall nutritional balance. Enjoying a variety of these foods regularly can help ensure you're getting an adequate intake of vitamin D for overall health and wellbeing.

Note: Materials provided above by University of Exeter. Content may be edited for style and length.

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