April marks Bowel Cancer Awareness Month, a timely opportunity to highlight the latest research on how diet, nutrition and physical activity can support patients living with, and beyond, colorectal cancer. A new report from World Cancer Research Fund (WCRF) International provides healthcare professionals with evidence-based insights to inform patient care and future research.
By Rachel Clark, Health Promotion Consultant, World Cancer Research Fund
The new report summarises the latest research on diet, nutrition, physical activity and body weight for people living with and beyond colorectal cancer.
The report also provides guidance for people living with and beyond colorectal cancer, as well as recommendations to the scientific community to take the research forward to better understand the impact of modifiable behavioural factors on cancer and non-cancer outcomes.
Background
Colorectal cancer is the third most commonly diagnosed cancer globally, accounting around for 1 in 10 new cancer cases in 2022.
Progress in early detection and treatment has significantly increased the number of years lived after a diagnosis. Although survival rates differ between countries, there are an estimated 5 million people worldwide who are living with or beyond a colorectal cancer diagnosis.
There is increasing demand for reliable, evidence-based guidance on diet and physical activity from health professionals and people living with and beyond cancer.
The available evidence
The available evidence on the effect of diet, nutrition, body weight and physical activity on the risk of cancer in cancer survivors is limited. When we refer to limited evidence in this context it means the available evidence may be limited by the amount of evidence in terms of the number of studies available, by inconsistency in the direction of effect, by methodological flaws (for example, lack of adjustment for known confounders) or by any combination of these factors. There is also a lack of evidence from randomised controlled trials – the gold standard of research trials which can help determine causality.
In addition, most published observational studies do not adequately account for factors such as cancer subtypes, the type and intensity of treatment, or the presence of other illnesses. It’s important to consider these, as they can impact the effect that various modifiable risk factors have on cancer outcomes.
The research included in our new report
Our research team at Imperial College London carried out a comprehensive analysis investigating the extent to which certain modifiable risk factors impact mortality (cancer-specific and all-cause) and risk of cancer recurrence in people after a colorectal cancer diagnosis.
Three systematic reviews were carried out, covering different exposures:
• diet (including supplements, alcohol and dietary patterns)
• physical activity and sedentary behaviour
• body weight
The report summarises the available evidence, provides guidance for people living with bowel cancer and makes recommendations for future research.
In total, data from 167 publications were analysed and an independent panel of experts graded the strength of the evidence from each review using our pre-determined grading criteria, to give a final evidence judgement on the certainty of the effect for each exposure.
The expert panel judged the strength of much of the evidence as limited which hampered their ability to develop recommendations for patients. Despite this, we consider it important that people living with and beyond bowel cancer can access reliable information based on the latest evidence.
The guidance described below has been developed using a robust and transparent process, incorporating input from expert clinicians and scientists, along with user input from health professionals and patients.
Summary of our guidance for people living with and beyond bowel cancer
This guidance is based on evidence graded as ‘limited-suggestive’. Limitations in the evidence meant that the panel could not be confident that associations were causal, so we cannot be sure that changes in the exposures would lead to changes in the outcomes. Despite the limitations in the evidence, this represents the best advice based on the current evidence and expert opinion.
General diet and lifestyle guidance
World Cancer Research Fund’s Recommendations for Cancer Prevention
World Cancer Research Fund have previously developed a set of 10 Cancer Prevention Recommendations based on strong scientific evidence. These Recommendations are a blueprint for individuals and societies to reduce their cancer risk. They are:
- Be a healthy weight
- Be physically active
- Eat wholegrains, vegetables, fruit and beans
- Limit ‘fast foods’
- Limit red and processed meat
- Limit sugar sweetened drinks
- Limit alcohol consumption
- Do not use supplements for cancer prevention
- For mothers: breastfeed your baby, if you can
- After a cancer diagnosis, follow our Recommendations, if you can
These are based on decades of research and many studies have now shown that following them reduces the risk of developing cancer.
One of these recommendations is that people living with bowel cancer follow the Cancer Prevention Recommendations as much as possible. This recommendation was made with caution because, although nutritional factors and physical activity appear to predict outcomes in people living with bowel cancer, there was insufficient evidence that changing these improves outcomes for this group.
The findings from this report (that healthy dietary and lifestyle patterns are associated with a lower risk of all-cause mortality, and unhealthy dietary patterns with a higher risk) are consistent with this guidance.
They found that ‘western’ diets (characterised by high intakes of processed foods, refined grains, red meat, processed meat, sugary drinks, and fried foods, while being low in fruits, vegetables, and fibre), and those which are pro-inflammatory and hyperinsulemic are associated with increased risk of all-cause mortality. Conversely, healthy dietary patterns, such as World Cancer Research Fund’s Cancer Prevention Recommendations, were associated with better outcomes.
We suggest that people living with bowel cancer consider following as many of the Cancer Prevention Recommendations as they can.
New specific guidance
The reviews looked at a wide variety of exposures including meat, dairy products, alcohol and supplements. The strength of the evidence was graded by an expert panel and the exposures below were graded as ‘limited-suggestive’ of an association with bowel cancer outcomes. For further information about the other exposures reviewed, which were graded as ‘limited-no conclusion’, see the full report.
Physical activity
People who are more physically active have better health outcomes after a diagnosis of bowel cancer. While it is uncertain that increasing physical activity will improve these outcomes, we suggest that people consider increasing their physical activity. However, physical activity should be increased under the supervision of health care professionals.
It may be particularly important for any increases in physical activity to be gradual, particularly for patients suffering from side-effects of their treatment, surgery, or from medication that may restrict their ability to be physically active, such as neuropathy or musculoskeletal issues.
Wholegrains
People who eat more wholegrains have better health outcomes after a diagnosis of bowel cancer. While it is uncertain that increasing wholegrains improves these outcomes, we suggest that people consider increasing their wholegrain intake.
Some patients may report difficulty consuming or digesting wholegrain foods following their treatment. This may be a particular issue following colon or rectal surgery.
Eating wholegrains can help contribute to fibre recommendations (in the UK the Scientific Advisory Committee on Nutrition recommend 30g per day from food sources) as well as provide valuable vitamins and minerals.
It’s advisable that patients who increase (or reintroduce) wholegrain foods into their diet do so gradually and as and when they can; this should be done under the supervision of a health professional, particularly after surgical intervention.
Coffee
People who consume more coffee (both caffeinated and decaffeinated) have better health outcomes after a diagnosis of bowel cancer. While it is uncertain that increasing coffee improves these outcomes, we suggest that people consider increasing their coffee intake.
The research observed a dose-response relationship, meaning the more coffee consumed the greater the benefits.
Another observational study funded by World Cancer Research Fund International found that people who drink more than 4 cups of coffee per day have a lower risk of the cancer recurring than those who have 2 or fewer cups. The study found that participants who drank more than 4 cups of coffee had a 32% lower risk of cancer recurrence than participants who drank less than 2 cups per day in terms of relative risk. In addition, the risk of dying was lower among coffee drinkers, and 3–5 cups of coffee per day seem sufficient to improve survival. However, more evidence is needed to confirm the effect we are seeing is causative rather than simply an association.
Caffeinated coffee can have a laxative effect or cause palpitations, so it’s advisable for patients to consider this when consuming coffee, or other caffeine-containing beverages (e.g. black or green tea) and foods (e.g. dark chocolate). It is also advisable for patients to consider how caffeine fits with any overall health concerns, such as sleep.
Sugary drinks
People who consume less sugary drinks have better health outcomes after a diagnosis of bowel cancer. While it is uncertain that decreasing sugary drinks improves these outcomes, we suggest that people consider decreasing their sugary drink intake, which is line with healthy eating guidelines for the UK and World Cancer Research Fund’s Cancer Prevention Recommendations.
We recommend that individuals living with and beyond cancer speak to their healthcare team before making any changes related to diet, nutrition, physical activity or body weight. Any healthcare professionals using this guidance should consider where a patient is in their cancer journey and interpret the guidance appropriately to suit each person’s individual needs.
“The best and most up-to-date body of evidence”
Dr Helen Croker, Assistant Director of Research and Policy at World Cancer Research Fund International, said:
“This comprehensive and rigorous review of the current state of evidence offers useful guidance on some of the diet and lifestyle factors that could improve cancer survival, and potentially help people living with and beyond cancer enjoy longer, healthier lives.
At the same time, it shows a clear need for more well-designed intervention and cohort studies to support the development of robust recommendations for colorectal cancer patients and health professionals. As we are seeing an increase of people diagnosed with colorectal cancer at younger ages, it is more important than ever that health advice is based on high-quality research.”
Dr Doris Chan, Senior Research Fellow in Nutrition at Imperial College London, and Dr Kostas Tsilidis, Reader in Cancer Epidemiology and Prevention at Imperial College London, the lead investigators of the reviews said:
“We analysed several hundred studies, and although most had limitations and potential biases, we are confident that it represents the best and most up-to-date body of evidence that can assist people living with or beyond cancer in making evidence-based decisions on lifestyle changes that can improve their well-being.”
Research on the effects of diet, nutrition and physical activity on health outcomes (including the risk of a future cancer and recurrence) in cancer survivors is growing and World Cancer Research Fund will continue to monitor the evidence
Recommendations for future research
The methodologies currently used in survivorship research need to improve to overcome some of the limitations in the current research. Stronger evidence can then be turned into information to the public, allowing World Cancer Research Fund to better support those living with and beyond colorectal cancer. Looking over all the reviews, we highlighted the following as important issues for future studies to address:
• Well-designed clinical trials and prospective cohorts are needed. These studies should account for differences in cancer sub-types, treatment types and other patient characteristics.
• Studies should aim to use the most accurate methods possible for assessing diet, nutrition, physical activity and body weight within populations living with and beyond cancer. They should include more accurate reporting of the timing of exposures.
• Novel methods for understanding the biological processes and mechanisms that underpin the associations we find in our cancer survivorship research are much needed.
• Research should aim to study more diverse populations.
Preventing bowel cancer
We estimate that around 67% of bowel cancer cases in men and 60% of cases in women could be prevented in the UK. Many of the risk factors for bowel cancer are related to diet and how active we are, so changing the way we live could have a big impact on the chances of developing it over our lifetime. Here are five practical actions, based on strong evidence, that people can take to reduce their risk.
1. Eat a healthy diet
There’s strong evidence that eating processed meat increases the risk of bowel cancer. Eating a lot of red meat can also increase risk. It is estimated that 14.5% of bowel cancer cases in men, and 10% in women, are attributable to consuming more than 25g of processed meat each day.
People should aim to limit their intake to no more than three portions (350–500g cooked weight) of red meat a week and avoid processed meat whenever possible.
There’s also strong evidence that eating more wholegrains protects against bowel cancer. Foods that contain fibre have also been shown to lower bowel cancer risk.
2. Be a healthy weight
It’s estimated that around 13% of bowel cancer cases in men, and 10% in women, are caused by excess weight. Keeping weight within a healthy BMI range and avoiding weight gain in throughout life can reduce the risk of bowel cancer.
3. Be physically active
There’s strong evidence that physical activity has a protective effect against bowel cancer. Being physically active can also help people to maintain a healthy weight. Adults should aim to do at least 150 minutes of moderate-intensity physical activity a week.
4. Don’t drink alcohol
There’s strong evidence that drinking alcohol increases the risk of bowel cancer. In the UK, it’s been estimated that drinking alcohol is linked to 13.5% of bowel cancer cases in men and 2% of cases in women. For cancer prevention, it’s best not to drink alcohol.
5. Don’t smoke
Stopping smoking will reduce a person’s risk of bowel cancer.
What about screening?
Most bowel cancer cases can be successfully treated if they are found early – that’s why it is important people take part in NHS bowel cancer screening whenever they are invited.
Read more about World Cancer Research Fund’s Cancer Prevention Recommendations.
Resources for people living with and beyond bowel cancer
1. Cancer and nutrition helpline
WCRF believe everyone who has been diagnosed with cancer should have access to the most reliable and up-to-date information about cancer and nutrition.
Their expert oncology dietitians are on hand to answer people’s questions on diet and cancer.
Their helpline is available on:
Tuesday 12–2pm and Thursday 6–8pm
Call: 0300 102 2523
Email: helpline@wcrf.org
2. Eat well during cancer guide
Eating well during cancer and cancer treatment can be challenging. This guide offers practical tips and advice to help navigate common side-effects and maintain a nutritious diet to support recovery and overall well-being.
3. Cook through cancer
WCRF’s award-winning online cookery classes are hosted by a professional chef and oncology specialist dietitian. The classes support people affected by cancer, including carers and loved ones.
4. Healthy living after cancer guide
This guide is for those who have finished their cancer treatment and provides tips and advice on how to stay healthy and reduce the likelihood of cancer recurring.
References
1. PubMed. Global colorectal cancer burden in 2020 and projections to 2040 [online]. 2021. Available at: www.pubmed.ncbi.nlm.nih.gov/34243011
2. World Cancer Research Fund CUP Global. Diet, nutrition, physical activity and body weight for people living with and beyond colorectal cancer [online]. 2024. Available at: www.wcrf.org/wp-content/uploads/2025/02/CUP-Global-COL-Report.pdf
3. International Journal of Cancer: Volume 155, Issue 3. Post-diagnosis adiposity, physical activity, dietary factors and cancer survival: A systematic review of the evidence base (WCRF Global Cancer Update Programme)[online]. 2024. Available at: www.onlinelibrary.wiley.com/toc/10970215/2024/155/
4. World Cancer Research Fund. Colorectal cancer statistics [online]. 2024. Available at: www.wcrf.org/preventing-cancer/cancer-statistics/colorectal-cancer-statistics
5. AMRC Open Research. Population attributable risk for colorectal and breast cancer in England, Wales, Scotland, Northern Ireland and the United Kingdom [online]. 2024. Available at: www.healthopenresearch.org/articles/3-11
6. International Journal of Cancer. Coffee consumption is associated with a reduced risk of colorectal cancer recurrence and all-cause mortality [online]. 2024. Available at: www.onlinelibrary.wiley.com/doi/10.1002/ijc.34879
