Dr Shireen Kassam and Dr Laura Freeman examine how eating a wholefood plant-based diet can affect cancer risk and recovery.
Cancer is a highly emotive subject and often presents many physical and emotional challenges.
One in two people in the UK will develop cancer in their lifetime. This means most of us know a friend of family member who have had such a diagnosis, or we might have even faced this ourselves.
Talking about cancer openly and objectively is helpful especially because 4 out of 10 cases could be prevented if we were all to adopt a healthy diet and lifestyle, including a diet centred around healthy plant foods1.
Yet when surveyed, less than half of the UK public were aware that processed red meat is a direct cause of cancer and that fruit, vegetables and fibre are protective.
In fact, vegan and vegetarian diets are associated with a significantly lower risk of developing cancer2.
This is because a diet almost or completely consisting of fruit, vegetables, whole grains, beans, nuts and seeds maximises the consumption of anti-cancer compounds found in food.
As a result, this leads to a healthier gut microbiome, lower levels of inflammation and cellular stress and a healthier body weight, which are all-important for preventing cancer.
Of course, diet alone cannot guarantee a life free of cancer. But what has emerged in the scientific literature is that a healthy plant-based diet can improve your chances of remission and survival after a cancer diagnosis.
For example, one of the largest studies conducted on diet and health in post-menopausal women called the Women’s Health Initiative reported that those participants assigned to consume more fruit, vegetables and whole grains had a longer remission and survival after a diagnosis of breast cancer3.
Similarly, in colorectal cancer, a more plant-based diet has been associated with a longer remission and survival4.
With regards to prostate cancer, men consuming more plant-based foods have a lower PSA level, a marker of prostate cancer growth5.
A seminal study by Dr Dean Ornish, a pioneer of lifestyle medicine, showed that a low-fat plant-based diet alongside other healthy habits can halt the progression of early-stage prostate cancer, with a direct impact on the expression of cancer-related genes6,7.
An exciting recent development is the recognition that the health of the gut microbiome impacts response and outcomes to therapies that target the immune system and that a fibre-rich diet abundant in healthy plant foods predicts for a longer remission8.
Furthermore, studies show the importance of a healthy diet for preventing second cancers and cardiovascular disease after a cancer diagnosis9.
Recent research has revealed a link between the health of the gut microbiome and the immune system.
While we don’t believe in superfoods as such, some plant foods do stand out when it comes to their anti-cancer properties.
Top of our list would be cruciferous vegetables of the Brassicaceae family whose leaves are shaped like a cross10.
Examples include broccoli, rocket, cabbage and Brussel sprouts. Their anti-cancer effects are thought to be due to the sulphur-containing compounds called glucosinolates.
Through cooking, chewing and digestion they are converted to compounds such as indole-3-carbinol and sulphoraphane, which act at a cellular level to prevent cancer.
A fun fact to know is that broccoli sprouts can have up to 100 times higher amounts of sulphoraphane than the broccoli heads. Mushrooms also appear to have particular anti-cancer properties.
A review of 17 observational studies concluded that consuming mushrooms at least five times per week lowered the risk of cancer by 44%11.
Mushrooms contain many compounds that may be responsible for the beneficial effects with beta-glucan thought to be one.
It is a type of fibre that has also been shown to benefit the immune system and interestingly is also found in nutritional yeast, which we vegans love!
Other foods to emphasise include tomatoes and other red-coloured fruit and vegetables that contain lycopene, a type of carotenoid, that has been associated with a lower risk of prostate cancer12.
The allium family of vegetables including onion, garlic and leeks contain beneficial sulphur compounds which have been associated with a lower risk of cancer, particularly stomach and oesophageal cancer13.
Cruciferous vegetables contain compounds called glucosinolates which have potent anti-cancer properties.
Learn more about how a plant-based diet can help you lead a healthy lifestyle here:
- How a wholefood plant-based diet can cut your risk of having a stroke
- Can a whole food plant-based diet relieve asthma symptoms?
- How eating a plant-based diet can ease the symptoms of menopause
One of the most underrated foods is soya. The consumption of minimally processed forms such as tofu, tempeh, edamame beans and soya milk has been associated with an array of health benefits and a reduced risk of many of our commonest cancers, including breast and prostate cancer14.
The anti-cancer properties are due to compounds called isoflavones, a type of phyto-oestrogen, which acts to slow down the growth of cancer cells. In addition, soya protein lowers cholesterol levels and is effective at building muscle.
The isoflavones also support bone health and can counter menopausal symptoms, all useful properties when recovering from cancer treatment.
Swapping cow’s dairy for soya milk is also an excellent option given that dairy consumption increases the risk of prostate cancer15 and may increase the risk of breast and endometrial cancer, whereas soya milk seems to have a protective effect16.
Swapping cow’s dairy for soya milk is an excellent option as dairy consumption increases the risk of prostate cancer.
Another source of phyto-oestrogens called lignans is flaxseeds. Most vegans incorporate flax into their diet as it is a rich source of short-chain omega-3 fatty acids.
It turns out that the lignan content is very useful for cancer prevention and has also been shown to slow the growth of cancer cells in the laboratory17.
In addition, 30g of flaxseeds a day has been shown to reduced blood pressure as effectively as medications18.
Overall we know that the best way to thrive on a plant-based diet is to eat a good variety of foods aiming for as many different colours as you can find.
This way you are supporting the health of your gut microbiome which is crucial in maintaining a healthy immune system and preventing the growth of cancer cells.
In addition, remember to incorporate regular physical activity to your routine, avoid tobacco and alcohol, prioritise sleep, manage stress and maintain healthy relationships.
These lifestyle factors are equally important for preventing and surviving well after a cancer diagnosis.
At Plant Based Health Online, we are supporting patients to adopt a healthy plant-based diet and other healthy lifestyle habits after they have completed their cancer treatment.
This is because we know how important this is to living well after a diagnosis of cancer.
Our group consultations provide peer support and expertise that cuts through the everyday confusion, supporting people to make sustainable changes that can also positively impact their loved ones too.
Plant-based diets are a powerful way to help prevent many illnesses.
Veronika Charvátová examines the impact of eating a vegan diet on our risk of developing dementia.
- Rock, C. L. et al. American Cancer Society guideline for diet and physical activity for cancer prevention. CA. Cancer J. Clin. (2020). doi:10.3322/caac.21591
- Dinu, M., Abbate, R., Gensini, G. F., Casini, A. & Sofi, F. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Crit. Rev. Food Sci. Nutr. (2017). doi:10.1080/10408398.2016.1138447
- Chlebowski, R. T. et al. Dietary modification and breast cancer mortality: Long-term follow-up of the Women’s Health initiative randomized trial. J. Clin. Oncol. 38, (2020).
- Guinter, M. A., McCullough, M. L., Gapstur, S. M. & Campbell, P. T. Associations of Pre- and Postdiagnosis Diet Quality With Risk of Mortality Among Men and Women With Colorectal Cancer. J. Clin. Oncol. (2018). doi:10.1200/JCO.18.00714
- Mouzannar, A. et al. Impact of Plant-Based Diet on PSA Level: Data From the National Health and Nutrition Examination Survey. Urology (2021). doi:10.1016/j.urology.2021.05.086
- Frattaroli, J. et al. Clinical Events in Prostate Cancer Lifestyle Trial: Results From Two Years of Follow-Up. Urology (2008). doi:10.1016/j.urology.2008.04.050
- Ornish, D. et al. Effect of comprehensive lifestyle changes on telomerase activity and telomere length in men with biopsy-proven low-risk prostate cancer: 5-year follow-up of a descriptive pilot study. Lancet Oncol. 14, (2013).
- Nomura, M. et al. Association of Short-Chain Fatty Acids in the Gut Microbiome With Clinical Response to Treatment With Nivolumab or Pembrolizumab in Patients With Solid Cancer Tumors. JAMA Netw. open 3, (2020).
- Perez, D. G., Loprinzi, C. & Ruddy, K. J. Lifestyle Factors Can Lead to Multiple Cancers over a Lifetime – Here We Go Again. JAMA Oncology 7, (2021).
- Royston, K. J. & Tollefsbol, T. O. The Epigenetic Impact of Cruciferous Vegetables on Cancer Prevention. Current Pharmacology Reports (2015). doi:10.1007/s40495-014-0003-9
- Ba, D. M. et al. Higher Mushroom Consumption Is Associated with Lower Risk of Cancer: A Systematic Review and Meta-Analysis of Observational Studies. Adv. Nutr. (2021). doi:10.1093/advances/nmab015
- Fraser, G. E., Jacobsen, B. K., Knutsen, S. F., Mashchak, A. & Lloren, J. I. Tomato consumption and intake of lycopene as predictors of the incidence of prostate cancer: the Adventist Health Study-2. Cancer Causes Control 31, (2020).
- Wan, Q. et al. Allium vegetable consumption and health: An umbrella review of meta-analyses of multiple health outcomes. Food Science and Nutrition (2019). doi:10.1002/fsn3.1117
- Li, N. et al. Soy and Isoflavone Consumption and Multiple Health Outcomes: Umbrella Review of Systematic Reviews and Meta-Analyses of Observational Studies and Randomized Trials in Humans. Molecular Nutrition and Food Research (2020). doi:10.1002/mnfr.201900751
- Aune, D. et al. Dairy products, calcium, and prostate cancer risk: A systematic review and meta-analysis of cohort studies. Am. J. Clin. Nutr. (2015). doi:10.3945/ajcn.113.067157
- Fraser, G. E. et al. Dairy, soy, and risk of breast cancer: those confounded milks. Int. J. Epidemiol. (2020). doi:10.1093/ije/dyaa007
- Parikh, M. et al. Dietary flaxseed as a strategy for improving human health. Nutrients (2019). doi:10.3390/nu11051171
- Caligiuri, S. P. B. et al. Flaxseed consumption reduces blood pressure in patients with hypertension by altering circulating oxylipins via an α-linolenic acid-induced inhibition of soluble epoxide hydrolase. Hypertension (2014). doi:10.1161/HYPERTENSIONAHA.114.03179