What is the impact of diet on cancer risk?

Dr Shireen Kassam MBBS, FRCPath, PhD, dipIBLM is a Consultant Haematologist, Honorary Senior Lecturer King’s College Hospital London and Visiting Professor Winchester University. Shireen will be speaking at the upcoming BGS Spring Meeting in Manchester. She specialises in the management of lymphoma at King’s College Hospital. She is also passionate about promoting healthy predominately plant-based diets for disease prevention and reversal. She runs an online course at Winchester University on plant-based diets aimed at health professionals in clinical practice. She is also a certified lifestyle medicine physician. Tweets via @plantbasedhpuk 

As we pass another World Cancer Day on 4 February 2020, I reflect on why I am passionate about promoting a healthy diet and lifestyle for cancer prevention. 1 in 2 people born after 1960 will develop cancer in their lifetime, and cancer is the commonest cause of premature death in the UK. Yet 40% of all cases of cancer could potentially be prevented through the adoption of healthy lifestyle behaviours. Dietary risk factors contribute significantly to the risk of cancer development such that 5 of the 9 cancer prevention recommendations published by the World Cancer Research Fund are related to diet. Despite international consensus on what constitutes a healthy diet, there remains confusion among the general public and health professionals alike, and the extent to which a healthy diet can reduce cancer risk is often not appreciated. 

What is the impact of diet on cancer risk? One study from the US that followed >100,000 men and women for 34 years found that those following a healthy diet could reduce their risk of dying from cancer by 30%. A further study from the same cohort revealed that a healthy diet and lifestyle not only improved life expectancy but these added years were lived without cancer and cardiovascular disease. So healthy diets not only add years to life but life to years.

My work involves treating patients with established cancer, in particular lymphoma. All my patients ask about what they can do to help their chances of recovery and what they should eat. Patients often feel a lack of control over healthcare decisions when it comes to cancer treatment yet diet is one aspect of their lives where they can maintain full control. These interactions provide teachable moments, because if patients are fortunate enough to be cured of their cancer, they often remain at higher risk of developing heart disease and secondary cancers and therefore a healthy diet is paramount. What is really exciting is that there is data emerging to suggest that diet choices after a diagnosis of cancer can positively impact the chances of remaining in remission and may improve survival rates. For example in the Women’s Health Initiative study, those women who developed breast cancer and were eating the most fruits, vegetables and whole grains had an improved survival. Similarly, a diet centred around healthy plant foods has been associated with improved survival after a diagnosis of colorectal cancer.

An emerging field of research is the impact of the gut microbiome on cancer outcomes. This relates particularly to treatment outcomes with therapies that activate the immune system. Early data suggest that those patients with a healthy gut microbiome, characterised by an increased number and diversity of bacterial species, have a better chance of responding to certain cancer treatments. This is a really exciting field of research because the health of the gut microbiome is intimately related to our diet choices and this opens up the potential to enhance cancer therapy through a dietary approach.

So come along to my talk at the BGS Spring Meeting in Manchester to hear about what constitutes a healthy diet for cancer prevention and treatment. The good news is that what is good for the heart and the brain is also good for cancer prevention.