Increasing fibre intake improves immunotherapy outcomes

Increasing fibre intake improves immunotherapy outcomes

A review in The Lancet Oncology, from researchers at MD Anderson in Texas argues that host factors rather than tumour-intrinsic features may play a greater role in the success or failure of new treatments like immunotherapy drugs; for example, fibre and probiotics can greatly affect the outcomes for patients undergoing immunotherapy (writes Gilly Bertram).

Patients with skin cancer who consumed a high fibre diet had improved outcomes from the immunotherapy treatment(1). The researchers found that diet and supplements appeared to affect the patients' response to the immunotherapy drugs and they attribute this development to the possible change in the patient’s gut microbiota.

Previous studies from MD Anderson(2). discovered that patients with large numbers of bacteria called Ruminococcaceae were higher responders to immunotherapy drugs targeting anti-PD1. And scientists are finding that patients with a more diverse microbiome have a better response to immunotherapy.

The latest study by Dr. Jennifer McQuade, Dr, Carrie Daniel and others at MD Anderson set out to explore the effect of diet and supplements on the microbiome to see if they were capable of modulating responses to a type of immunotherapy known as 'checkpoint therapy'. What they found was that whole grains and the overall quality of a person’s diet positively correlated with greater levels of health-promoting gut bacteria, which in turn linked with better health outcomes; while added sugars and processed meat diets correlated with unhealthful and disease promoting bacteria and worse outcomes.

Similarly, they compared people on a high fibre diet to a low fibre diet whilst undergoing treatment and found that people consuming a high fibre diet were five times more likely to respond to the immunotherapy treatment. The important role of fibre in human digestion could explain why scientists are seeing such positive outcomes in patients undergoing immunotherapy.

Chris Woollams, former Oxford University Biochemist and author of the best seller 'Heal your gut - heal your body' said, "All this makes perfect sense and we have known it for 6 years or so. If you eat good foods you boost commensal or good bacteria and they make a host of health promoting compounds. If you eat bad foods, you can promote pathogens in the gut which produce toxins and inflammatory molecules. In particular, your good bacteria love soluble fibre - oats, psyllium, vegetables, nut and seeds and pulses. People who consume the greatest levels of soluble fibre have the strongest immune systems, for example."

Go to: Soluble fiber intake boosts the immune system

The MD Anderson researchers felt that dietary fibre plays a vital role in our digestive systems and is essential for good health. Fibre is a form of non-digestible carbohydrates which is made up of long chains of glucose and other carbohydrate molecules. The best form of fibre comes from vegetables as they are more nutrient dense compared to grain fibre. Cellulose is one type of fibre, and others include lignin, pectin and chitin. These long chains of molecules are bonded together so strongly that they cannot be broken down by our digestive enzymes in our small intestine (where most of our digestion takes place), but only when it reaches our large intestine where our gut bacteria live can they be finally be broken down because it is those gut bacteria which have the enzymes to break down the fibre. The fibre feeds the bacteria as they break it down to release the glucose within. Feeding these bacteria is important as they are beneficial and essential for life.

It is important to feed our healthy gut bacteria as they also produce a compound called butyrate which protects the cells lining the intestines. Butyrate is also known to kill colorectal cancer cells.

The results of the study suggest that by modulating the gut microbiome by increasing intakes of dietary fibre, patients can improve their chances of benefitting from immunotherapy drugs. However, most people are going to benefit anyway from increasing vegetable fibre in their diets to have a healthier and diverse gut microbiome.

Ongoing cancer research in 39 clinical trials further investigating the effects of modulating the gut microbiome alongside immunotherapy agents was announced in the Lancet earlier in 2019 (1).

Go to: Comprehensive review of Immunotherapy drugs

Woollams added, "We also know from research that taking probiotics enhances chemotherapy and immunotherapy results, while taking antibiotics reduces effectiveness."



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