A healthy diet, in conjunction with regular exercise, has long been associated with prevention of serious diseases, including heart disease, type 2 diabetes, and cancer. 

But what about the effects of diet if you already have cancer? And how might the specialization of one’s diet affect how cancer therapies work?

Over the past few decades, the explosion of precision cancer therapy targeting specific genetic mutations in cancer cells has allowed clinicians to fine-tune how cancer is treated. 

Recently, immunotherapy, a newcomer to the anti-cancer treatment arsenal, has shown incredible success in treating different cancer types, including melanoma, certain types of lung cancer, bladder cancer, kidney cancer, and more.

What is immunotherapy?

Immunotherapy is a revolutionary cancer treatment that works by activating the immune system to destroy cancer cells.

The immune system is made up of a variety of cell types that work together to fight infection to keep us healthy. Immune cells are experts at recognizing anything that doesn’t belong in the body and facilitating its destruction. 

However, cancer cells have the ability to evade the immune system and hide in plain sight. There are a number of ways this might happen: cancer cells may look normal to the immune cells, allowing them to remain hidden; or, the immune system may recognize cancer cells as a threat, but may be unable to respond strongly enough to destroy the harmful cells.

Immunotherapy acts by removing the screens cancer cells hide behind that allow them to evade the immune system, which in turn, helps the immune system better recognize cancer cells in order to destroy them.

To learn more about how immunotherapy works, we’ve created a nifty online course here.

3D Rendering of a Natural Killer Cell (NK Cell) destroying a cancer cell
Immunotherapy prevents cancer cells from evading the immune system, which allows the immune system to destroy cancer cells. Pictured, a 3D rendering of a natural killer cell destroying a cancer cell.

How can diet affect how immunotherapy works?

Although immunotherapy has achieved great success, it does not always work for everyone. The immune system is complex, and understanding the various factors that influence its activity is essential to uncovering ways to make immunotherapy more effective.

Since a healthy diet is important for maintaining the health of the immune system, there is a lot of interest in understanding whether diet can impact the effectiveness of immunotherapy.

Diet is particularly important in influencing the makeup of our gut microbiome. A healthy, high-fiber diet promotes the growth of beneficial microbial species that break down fiber into  fatty acids that promote immune health.

As diet is a variable that can be relatively easy to control, the opportunity to improve treatment outcomes by following certain diets is likely to be important to those receiving immunotherapy. However, data on this topic are limited and evaluating specific dietary recommendations for individual cancer types is challenging due to multiple factors, including the variability and complexity of current dietary categorizations.

Correlative studies in melanoma have revealed that the gut microbiome appears to modulate the response to immunotherapy. In particular, in a study published in 2018, high gut microbiome diversity and abundance of Ruminococcaceae/Faecalibacterium was associated with a better response to anti PD-1 immunotherapy, while low gut microbiome diversity and abundance of Bacteroidales was associated with a worse response.

A more recent study from the same research group looked at how the use of probiotics and antibiotics, and dietary fiber affected gut microbiome diversity and response to immunotherapy in people with melanoma. The researchers showed that gut microbiome diversity was greatest in people with melanoma who had a complete or partial response to immunotherapy. In addition, use of probiotics or antibiotics was associated with reduced gut microbiome diversity, and a high-fiber diet was associated with greater odds of treatment response. Response was also positively correlated with a better overall diet and inclusion of whole grains, while it was negatively correlated with inclusion of added sugars and processed meat.

Food and drink large arrangement with carbohydrates protein vegetables and fruits legumes and dairy products on rustic board table.
A fiber-rich diet that minimizes processed foods could benefit the gut microbiome, which in turn improves the efficacy of cancer immunotherapies.

The authors suggest that the gut microbiome can be “targeted by dietary manipulation”, although further studies are needed in larger groups of people. Overall, however, these results are a promising start to more interventional controlled studies in people receiving cancer immunotherapy.

As of the writing of this blog, over 2,000 clinical trials in the US were found following the search for “diet” and “cancer”. When narrowed down to “diet” and “cancer” and “immunotherapy”, just under 50 trials were found, demonstrating that this is still a very early, but promising research field.

Looking to the future, perhaps we can imagine that a complete cancer treatment plan may also include a comprehensive, personalized diet plan that maximizes treatment effectiveness.