Why two sisters and cancer doctors wrote a book on plant-based diets

It may seem an unlikely topic for two cancer doctors to write about. Yet for us, after adopting a plant-based diet nearly a decade ago, it felt like the obvious book to write. In addition to our conventional hospital-based work in London and Toronto, we are both certified lifestyle physicians and run non-profit organisations in our respective countries that provide education and advocacy on healthy plant-based diets for prevention and treatment of chronic conditions.

The role of a plant-predominant or plant-exclusive diet for cancer prevention is well established in scientific literature and the World Cancer Research Fund guidelines on cancer prevention recommend a diet centred around fruit, vegetables, whole grains and beans. In our clinical practice, however, we are seeing patients with established cancer and are mainly dealing with issues related to co-morbidities, treatment toxicity and cancer survivorship. Although we have understood the role of healthy lifestyles in improving quality of life and survival after a cancer diagnosis, the literature on the role of plant-based diets or healthy plant foods has emerged more recently. Examples include the long follow up from the Women’s Health Initiative study reporting that those participants randomised to consuming more fruit, vegetables and whole grains had a longer remission and survival if they received a diagnosis of breast cancer. Similarly, in colorectal cancer, there are data supporting a more plant-based diet for improving remission duration and survival. With regards to prostate cancer, people consuming more plant-based foods have a lower PSA level and a low-fat plant-based diet alongside other healthy habits was shown long ago to halt the progression of early-stage prostate cancer, with a direct impact on gene expression. The most exciting development is the recognition that the health of the gut microbiome impacts response and outcomes to immune therapies and that a fibre-rich diet abundant in healthy plant-foods predicts for a better cancer outcome. Furthermore, studies show the importance of a healthy diet for preventing second cancers and other chronic conditions after a cancer diagnosis.

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Without fail our patients ask us about diet choices and overtime we have developed our own ways of providing dietary counselling within the confines of a short consultation. Asking some key questions on how many portions of fruit, vegetable and beans they eat a day, whether they eat red and processed meat and how much cooking they do versus preparing of ready meals, helps us gain a quick understanding of their diet quality. Our patients usually share with us some common engrained beliefs about the requirement for meat, the superiority animal protein, the need for dairy for calcium and the fear of ‘carbs’.

We have found that key moments for education tend to be at a person’s first consultation with us and at the completion of treatment when they may feel more ready to take back control of their lives. We endeavour to assess our patient’s ability and motivation to make changes and their social and financial situations. This can be very variable with some patients truly living in poverty and isolation, both situations worsened by the pandemic, and others having very supportive and secure family environments. Regardless, most people are able to make some healthy swaps. We focus on easy wins such as swapping refined grains for whole grains, dairy milk for soy, adding in at least on portion of green vegetables a day and using fruit for snacks. We try and give culturally appropriate advice based on the patients’ dietary preferences and tastes. We are very clear with our advice on processed and unprocessed red meat, processed food, and alcohol, that the potential harms clearly outweigh any perceived benefits. We signpost patients to helpful resources including online and community cooking opportunities. During the course of their treatment and follow up we have the opportunity to reinforce these messages and encourage more changes.

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The reason for writing this book was to provide patients and health care professionals with an easy access resource to commonly asked questions that we have now been answering for years. We hope this will give people the confidence to embrace a healthy plant-based diet and truly understand that it is the right decision for their health and all those we share this planet with. Supported by hundreds of scientific references, those who want to delve deeper into literature will find the book a useful place to start. We start the book covering common questions on eating meat, dairy, fish and eggs and then move on to questions on plant foods, their impact on health, myths about vegan diets and also the wider benefits to the planet and other animals. You can read the first chapter of our book for free on the publisher’s website and we have also shared the chapter of eating eggs on our website.

About the authors

Shireen Kassam MB BS, FRCPath, PhD, DipIBLM

Dr Shireen Kassam is a Consultant Haematologist and Honorary Senior Lecturer at King’s College Hospital, London with a specialist interest in the treatment of patients with lymphoma (cancer of the lymphatic system). She is also passionate about promoting plant-based
nutrition for the prevention and reversal of chronic diseases and for maintaining optimal health after treatment for cancer. Shireen qualified as a medical doctor in 2000, initially training in general medicine, and gaining Membership of the Royal College of Physicians (MRCP) in 2003. She then specialised in Haematology and achieved Fellowship of the Royal College of Pathologists (FRCPath) in 2008. During training, she took time out to undertake a PhD (University of London, 2011). Her research investigated the role of selenium, an essential micronutrient, in sensitising cancer cells to chemotherapy. She was able to show that supra-nutritional doses of selenium could enhance the action of chemotherapy in the laboratory. She has published a number of peer-reviewed papers in the field of lymphoma.

She discovered the power of nutrition for the prevention and treatment of disease in 2013 and since then has been following a whole-food plant-based diet. She has immersed herself in the science of nutrition and health and completed the eCornell certification in plant-based nutrition. In 2019 she became certified as a Lifestyle Medicine Physician by the International Board of Lifestyle Medicine. She is also a certified CHIP (Complete Health Improvement Program) practitioner.

Shireen founded Plant-Based Health Professionals UK in 2018, a community interest company whose mission is to provide evidence-based education and advocacy on plant-based nutrition. Since then, she has been appointed as Visiting Professor of Plant- Based Nutrition at Winchester University where she developed and facilitates the UK’s only university-based CPD-accredited course on plant-based nutrition for healthcare professionals. In January 2021, she co-founded and launched the UK’s first CQC (Care Quality Commission) registered, online, multi-disciplinary, plant-based lifestyle medicine healthcare service, Plant Based Health Online. She is also a member of the Research Advisory Committee for the Vegan Society. Her work has been published by The Times, Mail Online, The Mirror, Metro, Vice, Plant Based News and BBC Food. She is an acclaimed national and international speaker and is featured in the 2021 documentary Eating Our Way to Extinction.

Zahra Kassam MB BS, FRCPC, MSc, DipABLM

Dr Zahra Kassam is a Radiation
Oncologist at the Stronach Regional Cancer Centre in Ontario, Canada, and an Assistant Professor in the Department of Radiation Oncology at the University of Toronto. Zahra received her medical degree from the Imperial College of Science, Technology and Medicine in 1995, completed her specialist training in Clinical Oncology in the UK, followed by three years of clinical and research fellowship training at the Princess Margaret Cancer Centre, Canada, with a Masters in Clinical Epidemiology at the University of Toronto.

Her areas of clinical practice are in gastrointestinal and breast cancers. She has published a number of peer-reviewed papers on these malignancies, as well as in education and mentorship.

A few years ago, Zahra discovered the significant body of evidence demonstrating the benefits of nutrition in the prevention and management of chronic diseases, not taught at any stage of her medical training. She is a certified Lifestyle Medicine Physician with the American Board of Lifestyle Medicine and has completed the eCornell certification in plant-based nutrition and the Plant-Based Nutrition course at the University of Winchester. Zahra co-founded Plant-Based Canada, a non-profit organisation, in 2019, with the goal of educating the public and health professionals on the evidence-based benefits of plant-based whole food nutrition for individual and planetary health. Their inaugural event was held in 2019, the first Canadian Plant-Based Nutrition conference in Toronto.