There is general agreement that lifestyle, including diet, impacts risk of cancer, although the extent to which this is true varies greatly among specific types of cancer. This may be due in part to the fact that cancer is not a single disease; it is actually different cancer types with different etiologies.
The best available evidence relating diet, nutrition, physical activity and cancer comes from World Cancer Research Fund (WCRF) International and the American Institute for Cancer Research (AICR). The WCRF and AICR are the leading global authorities in cancer prevention research related to lifestyle.
- In the UK, excess weight is second only to smoking as the leading cause of 12 cancers including breast and bowel cancers.
- 40% of cancer cases could be prevented through improved dietary and lifestyle habits.
In 2018, the WCRF expert report laid out a 10-point plan for healthy lifestyle choices which would significantly impact on people’s likelihood of developing cancer. The guidelines are based on a review of more than 50 million people (the largest cancer study ever conducted).
- Be a healthy weight. Keep your weight within the healthy range and avoid weight gain in adult life.
- Be physically active. Be physically active as part of everyday life – walk more and sit less. Aim for 150 minutes a week of moderate intensity activity, or 75 minutes of vigorous activity per week.
- Eat a diet rich in wholegrains, vegetables, fruit and beans. Make wholegrains, vegetables, fruit, and pulses (legumes) such as beans and lentils a major part of your usual daily diet.
- Limit fast foods. Limiting processed foods high in fat, starches or sugars helps control calorie intake.
- Limit red and processed meat. Eat moderate amounts of red meat and little, if any, processed meat
- Limit sugar sweetened drinks. Drink mostly water and unsweetened drinks.
- Limit alcohol consumption.
- Do not use supplements for cancer prevention. Aim to meet nutritional needs through diet alone.
- For mothers: breastfeed your baby, if you can. Breastfeeding is good for both mother and baby.
- After a cancer diagnosis: follow the above recommendations, if you can. Check with your health professional what is right for you.
In conclusion according to the WCRF experts there is growing evidence that not smoking, keeping a healthy weight, eating and drinking healthily and being more active all helps to reduce cancer risk (https://www.wcrf.org/dietandcancer).
In general these guidelines emphasise a more plant-based eating pattern. Plant-based foods and eating patterns are typically low in saturated fat and high in fibre and usually have a low energy density which is useful in maintaining healthy body weight. The lower prevalence of obesity amongst plant-based eaters, as well as the nutritional characteristics of plant-based dietary patterns, are in line with recommendations aimed at reducing cancer risk.
Cancer survivors are people who have been diagnosed with cancer, including those who have recovered from the disease. The WCRF experts agree that the overall cancer prevention recommendations are also relevant to cancer survivors and recommend that, as far as possible, cancer survivors should aim to follow these recommendations post treatment (https://www.wcrf.org/dietandcancer).
More specifically, the Expert Panel of WCRF in its Continuing Update Programme, has reviewed the evidence for the effect of lifestyle factors on the survival and future risk of breast cancer patients. Breast cancer is the most common cancer in women and breast cancer incidence increased worldwide by 20 per cent between 2008 and 2012. In general survival rates for breast cancer have improved. The reason is twofold: (1) the majority of breast cancer cases are diagnosed at an earlier and localised stage; and (2) improved treatments are available.
There is growing evidence of links between better prognosis after breast cancer and several lifestyle choices, more specifically (https://www.wcrf.org/dietandcancer/breast-cancer-survivors):
- keeping a healthy body weight
- being physically active
- eating foods containing fibre
- eating foods containing soya
- a lower intake of total fat and, in particular, saturated fat
According to WCRF there may be links between better prognosis of breast cancer and 1) healthy body weight 2) being physically active 3) eating foods containing fibre 4) eating foods containing soya and 5) a lower intake of total fat, especially saturated fat. Additionally, the World Cancer Research Fund (2018) concluded there may be an association between consuming soya-based foods and a better prognosis following breast cancer
There is now impressive human data from epidemiologic studies indicating that soya foods do not worsen the prognosis of breast cancer patients.
A meta-analysis of 5 prospective studies (2 from US and 3 from China) which included over 11,000 women who had had breast cancer, and who were followed up for periods ranging from 4 years to over 7 years, found that consuming soya after their disease had been diagnosed, was associated with a significant reduction in cancer recurrence risk and mortality.
In the largest study (carried out in Shanghai) with over 5,000 patients followed up for nearly four years women consuming the most soya protein (< 15.3 g/day), had a 30% lower mortality rate and incidence of recurrence of the disease than those with smaller intakes (≤ 5.3 g/day).
It is important to note that the protective effect of soya consumption is observed in both Asian women and non-Asian women. In the 2 US studies amongst mainly with Caucasian women high intake of soya was also associated with a better prognosis for breast cancer.
This study reconfirms that consumption of soya foods is perfectly safe for women facing breast cancer.
American Inst. for Cancer Research. Soya is safe for breast cancer survivors [Internet]. 2012 [cited 13th April 2018]. Available from: http://www.aicr.org/cancer-research-update/2012/november_21_2012/cru-soya-safe.html
Baglia ML, Zheng W, Li H et al. The association of soya food consumption with the risk of subtype of breast cancers defined by hormone receptor and HER2 status. Intern J Cancer. 2016;139(4):742-8.
EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). Risk assessment for peri- and post-menopausal women taking food supplements containing isolated isoflavones. EFSA J. 2015;13(10):4246, 342 pp.
Shu XO, Zheng Y, Gu K, Cai H, Zheng W. Soya food intake and breast cancer survival. JAMA 2009;302:2437-43.
WCRF. Diet, Nutrition, Physical Activity and Cancer: a global perspective - The Third Expert Report. 2018. Washington, AICR.
Ref Type: Report
WCRF Intern. Continuous Update Project. Breast cancer survivors: how diet, nutrition and physical activity affect breast cancer survival [Internet]. 2018 [cited 7/24/2018]. Available from: https://www.wcrf.org/dietandcancer/breast-cancer-survivors