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BLOG BY Fiona Malcomson - @Fiona.Malcomson

Healthier Lifestyles for Cancer Prevention

Our risk of getting diseases such as certain cancers can be divided into non-modifiable and modifiable risk factors. Non-modifiable factors, that we cannot control, include things like age or having a strong family history of a particular disease. Modifiable risk factors include lifestyle and environmental factors, such as diet, body weight and exercise. In the UK, about 40% of cancers are linked with lifestyle factors such as a poor diet, overweight & obesity, and smoking (Brown et al, 2018).

Quite worryingly, a large proportion of the public are not aware of the links between certain lifestyle behaviours and cancer risk. In a survey run by the World Cancer Research Fund (WCRF), only 62% were aware that an unhealthier diet was associated with a greater risk of developing cancer (Sakula-Barry, 2019). In the UK, only about 15% of people know about the links between obesity and cancer risk.

The World Cancer Research Fund Cancer Prevention Recommendations

The WCRF is the world’s leading authority on research into lifestyle and cancer prevention. In 2007, the WCRF published lifestyle-related Cancer Prevention Recommendations and, in 2018, these were updated to reflect the latest research findings (WCRF/AICR 2018

1 Be a healthy body weight

Overweight and obesity are the second largest cause of cancer in the UK and are known to increase the risk of at least 13 cancers. Excess adiposity increases cancer risk by several different ways or mechanisms, that most likely act synergistically. These include the promotion of chronic inflammation, uncontrolled cell growth, insulin resistance, abnormal hormone levels and alterations to our gut bacteria (Iyengar et al, 2015)

2. Be physically active

Physical activity describes movements that use skeletal muscles and expend energy. We are recommended to do at least 150 minutes of moderate physical activity (e.g. walking or cycling) or 75 minutes of vigorous physical activity (e.g. running) per week. Lower risk of cancers such as breast cancer, colon cancer and endometrial cancers have been observed with greater levels of physical activity. It might not just be the amount of physical activity that we do, but also the type (Rezende et al, 2020). Strength training (e.g. lifting weights) has also been associated with reducing cancer risk and improving cancer survival. Directly, exercise can alter cancer risk by reducing levels of inflammation in our body, improving our immune function, helping our cells to repair DNA and regulating hormone levels. Indirectly, it can also reduce our cancer risk by promoting a healthy body weight.

3. Eat wholegrains, vegetables, fruit and beans

In the UK, we are recommended to eat at least 30g of dietary fibre per day. However, on average, we are consuming only around 18g (for more information on dietary fibre, please see: https://rhitrition.com/how-does-dietary-fibre-benefit-our-gut-health/ ). A review of 25 studies concluded that every 10g dietary fibre intake per day was associated with a 10% reduction in colorectal cancer risk (Aune et al, 2011). Its perhaps not surprising that most of the evidence for dietary fibre and cancer risk is for colorectal cancer, as dietary fibre reaches the large bowel undigested. Here, directly, it reduces the exposure of the large bowel lining to carcinogens by increasing the bulk of material passing through and reducing the time it takes for this to travel through. When broken down by the gut bacteria (microbiota) in our large bowel, short-chain fatty acids (e.g. butyrate) with anti-cancer properties are also produced. Dietary fibre, and butyrate, may also decrease colorectal cancer risk via effects on inflammation, insulin sensitivity, cell growth, bile acid concentrations and on the immune system.

We should also aim to eat a minimum of 5 portions of fruits and vegetables every day; each portion being about 80g (depending on the type of fruit or veg) and includes fresh, frozen or canned varieties (www.nhs.uk/live-well/eat-well/5-a-day-what-counts/ ). In the European Prospective Investigation into Cancer and Nutrition (EPIC) Study, one of the largest studies of its kind, lower fruit consumption was associated with increased risk of cancers of the upper gastrointestinal tract e.g. mouth and oesophageal cancers. People who ate the most fruit and vegetables also had a 14% lower risk of colorectal cancer compared with those who consumed the least (Bradbury et al, 2014).

4. Limit the consumption of “fast foods” and other processed foods high in fat, starches or sugars and limit sugar-sweetened drinks

The consumption of energy-dense and processed foods, such as burgers and confectionery, as well as sugar-sweetened drinks, indirectly increases the risk of cancer via promoting weight gain, overweight and obesity (discussed above). Additionally, via effects on blood glucose and insulin sensitivity, there is strong evidence for an effect on the risk of endometrial cancer (WCRF/AICR 2018). In particular, ‘ultra-processed’ foods, which are of low nutritional quality, contain additives and are exposed to packaging, such as instant noodles and fizzy drinks, which may increase cancer risk (Fiolet et al, 2018). Research into the impact of ultra-processed foods on health is very much ongoing

5. Limit red and processed meat

Strong evidence exists for an increased risk of colorectal cancer with higher consumption of red (e.g. beef and lamb) and processed (e.g. ham and bacon) meats. The WCRF advise to eat no more than 500g (cooked weight) of red meat per week which is approximately 3 portions, and to limit the consumption of processed meats to ideally less than 21g per week (Shams-White et al, 2019). A 35% and 31% increase in risk of colorectal cancer has been observed for red and processed meat, respectively, in those consuming the greatest amounts (Norat et al, 2002). There are several mechanisms via which red and processed meats can increase the risk of colorectal cancer, mainly via their haem content and production of chemicals during processing or cooking such as nitrates, nitrites, heterocyclic amines (HCAs) and polycyclic amines (PCAs) that are potential carcinogens. For more information, on red and processed meat and health, take a look at: https://rhitrition.com/how-much-red-meat-should-you-be-eating/

6. Limit alcohol consumption

Alcohol consumption, even in ‘light’ drinkers, increases the risk of several cancers, including breast, colorectal and liver cancer (Bagnardi et al, 2014). Cancer research bodies, such as the WCRF and Cancer Research UK, therefore advise against drinking any type of alcohol. Although the mechanisms underlying the effects of alcohol on cancer risk are not fully understood, these likely include effects on the production of reactive oxygen species and DNA damage, and increase in oestrogen as well as acetaldehyde production (a metabolite of alcohol) (Boffetta and Hashibe, 2006)

7. Do not rely on supplements

The evidence from research studies in humans for the modulation of cancer risk with dietary supplements, such as calcium and vitamin D, is limited. The WCRF therefore advise against the consumption of dietary supplements for cancer prevention. It is best that we try to reach our recommended dietary intakes through eating whole foods. However, supplementation may be required due to other factors, such as taking vitamin D supplements in the UK during the winter months to prevent vitamin D deficiency.

Links between following these recommendations and cancer risk

Since these recommendations, both the 2007 and 2018 versions, have been published, several observational studies have looked at whether people who stick to these more have different risks of cancer and cancer survival (for a list of relevant studies, go to: https://www.wcrf.org/dietandcancer/evidence-that-our-cancer-prevention-recommendations-work/ ). For example, in the NutriNet-Santé Study, performed in more than 40,000 participants, a 12% reduction in total cancer risk was observed per 1-point increase in adherence score (Lavalette et al 2018). In the UK Women’s Cohort Study, conducted in over 35,000 women, those who followed the WCRF recommendations the most had a 27% lower risk of getting colorectal cancer (Jones et al 2018).

What about other dietary and lifestyle patterns?

As we don’t eat individual foods and nutrients in isolation, but rather eat meals and a range of foods throughout the days and weeks, it is also important to look at relationships between overall lifestyle and dietary patterns and the risk of diseases too. For example, dietary patterns such as the Mediterranean Diet and a traditional Japanese diet (Abe et al 2021) have been associated with a reduced risk of non-communicable diseases, such as heart disease and some cancers.

A Mediterranean Dietary pattern, characterised by a higher consumption of fruits, vegetables, wholegrains, fish healthy fats i.e. olive oil, and a limited intake of red meat, processed foods and added sugars, has been described as the healthiest dietary pattern worldwide and has been associated with a reduced risk of diseases such as cardiovascular disease (Sofi et al, 2010). A systematic review, which is a robust ‘review’ of studies which focus on a particular research question, including over 2 million participants from 83 studies found an inverse association between following a Mediterranean dietary pattern and risk colorectal and breast cancers (Schwingshackl et al, 2017). Furthermore, in a randomised controlled trial (the gold-standard of research studies) conducted in Spain, women who followed a Mediterranean diet with additional extra-virgin olive oil or nuts for approximately 5 years had a 51% lower risk of malignant breast cancer compared with the control group (Toledo et al, 2015). It must be noted, however, that i) this was a secondary analysis of the PREDIMED study and ii) the participants were those at higher risk of cardiovascular disease.

Given that vegetarian and vegan diets are characterised by a high intake of plant-based foods such as fruits and vegetables, dietary fibre such as pulses, and no intake of red and processed meats, it is perhaps unsurprising that some evidence points towards a reduction in cancer risk with these diets. However, the evidence to date is limited and shows conflicting findings according to cancer site. For example, a study which reviewed the evidence to date found a reduction in the risk of colorectal cancer in semi-vegetarians vs. non-vegetarians, but not in relation to breast or prostate cancer (Godos et al, 2017). 

Other lifestyle factors and cancer risk

Approximately 15% of cancers in the UK are linked with smoking, making it the largest cause of cancer (Brown et al, 2018). Passive smoking is also a risk factor for lung cancer. The best way to reduce your risk of cancer is therefore to stop, or cut down on, smoking.

In addition to physical activity, sedentary behaviour (time spent sitting or lying down, but not sleeping), such as that during TV viewing and during sedentary jobs, may be an independent risk factor for the risk of some cancers, for example colon and endometrial cancer (Schmid and Leitzmann, 2014).

Exposure to UV radiation from the sun or sunbeds causes damage to our skin, its cells and DNA, and increases the risk of developing skin cancers. Up to 90% of melanoma skin cancers could be prevented by protecting ourselves adequately from the sun, for example by using sunscreen lotion of at least SPF15 and avoiding direct sunlight during peak hours in the summer, and not using sunbeds (Cancer Research UK).

Take home message

Approximately 40% of cancer cases in the UK may be prevented by leading a healthier lifestyle, for example maintaining a healthy body weight, undertaking regular exercise, limiting alcohol intake and eating a healthy diet, rich in wholegrains, fruits and vegetables. Cancer Prevention Recommendations have been produced by the WCRF, based on a robust review of the latest scientific evidence, to guide the general public to reduce their risk of developing cancers as well as other non-communicable diseases e.g. type 2 diabetes. Additional dietary patterns have also been observed to reduce the risk of cancers, such as the Mediterranean Diet.

Additional lifestyle and dietary factors can also affect our risk of getting cancer. For example, limiting the exposure to UV radiation from sunshine is important for the prevention of skin cancers. There are also additional foods e.g. fish, and micronutrients e.g. calcium, for which the evidence in relation to cancer risk is limited and inconclusive. Further, the contribution of individual lifestyle components to cancer risk may vary according to cancer site- for example, the consumption of red and processed meat is most relevant to bowel (colorectal) cancer. Lastly, no matter how healthy a lifestyle we lead, this does not guarantee that we will not get cancer, as there are non-modifiable risk factors that we cannot control.

Bio:

Dr. Fiona Malcomson BSc (Hons) MRes PhD is a Research Associate at Newcastle University with a PhD in Molecular Nutrition, and is also currently undertaking a Clinical Nutrition MSc at the University of Aberdeen. Fiona’s primary research interest is exploring the relationships between diet and other lifestyle factors and markers of large bowel health and of bowel cancer risk. Fiona has recently been awarded a grant by the WCRF to investigate relationships between adhering to the WCRF Cancer Prevention Recommendations and cancer risk and survival in the UK. Fiona is passionate about breaking down complicated science so it’s accessible for everyone and contributing to evidence-based nutritional and lifestyle public health recommendations through her research.

Instagram: @Fiona.Malcomson

Twitter: @FionaMalcomson

References

Abe et al (2021) European Journal of Clinical Nutrition 75:929-936

Aune et al (2011) BMJ 343:D6617

Bagnardi et al (2014) British Journal of Cancer 112:580

Boffetta and Hashibe (2006) The Lancet Oncology 7(2):149

Bradbury et al (2014) American Journal of Clinical Nutrition 100(Supp 1):394S-8S

Brown et al (2018) British Journal of Cancer 118, 1130

Cancer Research UK https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/can-cancer-be-prevented-0 [accessed January 2021]

Fiolet et al (2018) BMJ 360 :k322

Gill et al (2021) Nat Rev Gastroenterol Hepatol 18:101

Godos et al (2017) Public Health Nutrition 30(3):349

Jones et al (2018) British Journal of Nutrition 119(3):340-348

Kerr, Anderson and Lippman Parkin and Walker, 2011

Lavalette et al (2018) Cancer Research 78(15):4427-35

Rezende et al (2020) Br J Cancer 123666–672

Sakula-Barry 2019 https://www.wcrf-uk.org/uk/blog/articles/2019/03/do-people-really-know-what-causes-cancer [accessed January 2021]

Schmid and Leitzmann (2014) J Natl Cancer Inst. 16;106(7)

Schwingshackl et al. (2017) Nutrients 9(10):1063

Shams-White et al (2019) Nutrients 11(7):1572

Sofi et al (2010) The American Journal of Clinical Nutrition 92(5)1189

Toledo et al (2015) JAMA Intern Med. 175(11):1752

WCRF/AICR.  Continuous Update Project Expert Report 2018. Diet, Nutrition, Physical Activity and Colorectal Cancer. Available at dietandcancerreport.org

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