Cancer is a complex, multifactorial disease that develops over the lifespan. While many factors are at play, including genetic predisposition, environmental exposures can serve as a driving force in initiating tumour development and progression.¹

According to current knowledge, 80–90% of malignant tumours are caused by external environmental factors (carcinogens).² As many environmental exposures arise from human behaviour, awareness of modifiable risk factors can motivate patients to prioritise prevention through making positive lifestyle choices.

Altering the internal terrain

Diet, lifestyle and environmental exposures alter the inner terrain of the body to influence carcinogenic risk. Many factors coalesce to change the internal environment, and over time, may contribute to the initiation and progression of cancer (see Figure 1).³

Figure 1. Mechanisms of carcinogenesis and development of cancer.³

Deterioration in the cellular environment, mitochondrial hypofunction and cellular stress due to various factors may increase carcinogenesis and cancer development, in conjunction with predisposing genetic factors, stress and dysregulated immune system function.³

Dietary influences – for better or for worse

Diet is a key factor affecting the internal milieu and shaping carcinogenic potential. Low intake of fruit and vegetables, consumption of red and processed meat, inadequate dietary fibre, and excessive salt (sodium) intake have convincing causal relationships with cancer.²

High energy and high fat intakes increase rates of overweight and obesity, a compounding factor increasing cancer risk.² Overeating reduces the control of carbohydrates and fat metabolism and increases the levels of saturated fat, triggering chronic inflammation.³

Research suggests that a predominantly plant-based diet reduces the risk of cancer by 18–40%.^5,6 The EPIC research showed that consuming large amounts of vegetables has a protective effect on cancer onset in patients with a positive family history.⁶ In the Nurses’ Health Study II, which observed 86,000 women for >26 years, a strong (20%) reduction in breast cancer incidence was seen in women consuming large amounts of fruit and vegetables.²

Optimising health of the intestinal microbiome with healthy foods may be an important step in cancer prevention.³ Wholefoods, fresh fruits and vegetables, legumes, nuts, and seeds can be sources of beneficial nutrients, phytochemicals and fibre which support the intestinal microbiome, thereby influencing many aspects of health including nutrient absorption, immune function, and metabolism.

The protective effects of physical activity

Regular physically activity lowers cancer risk. According to the Australian Cancer Council, physical inactivity is responsible for 14% of colon cancers and 11% of postmenopausal breast cancers, and likely contributes to many other cancers.⁷

Those living a sedentary lifestyle are more likely to be overweight which, in turn, increases the levels of circulating oestrogens, androgens, insulin and insulin-like growth factors related to the growth of cells as well as tumours. Reduced physical activity also leads to increased exposure of breast tissue to circulating hormones and slows transit time (extending food retention in the large intestines and increasing potential mutagenic effects).² Obesity and low physical activity have been associated with an increased risk of colorectal cancer.⁴

Epidemiological evidence indicates that people who are more physically active have a lower risk of certain malignancies than those who are inactive,¹ highlighting the importance of maintaining an active lifestyle.

The strong case to quit smoking

Cigarette smoking has been conclusively linked with the formation of several malignancies and avoidance of smoking has been shown to reduce cancer incidence.¹ Smoking is known to cause lung cancer and is a major risk factor in cancers of the mouth and throat, stomach, cervical, kidney and liver, pancreatic, bladder, and blood (acute myeloid leukaemia).⁸

At least 400 of the 4,000 chemicals identified in tobacco smoke are known to be harmful to human health, with almost 10% of these toxic chemicals classified as carcinogenic.¹ Passive smoking is also a risk, as the ambient smoke from cigarettes is four times more harmful than that inhaled by the smoker.²

Supporting patients to quit smoking is a priority for long-term health.

Sobering advice on alcohol

Classified as a carcinogen by the World Health Organisation, regular alcohol intake has an impact. Having more than two drinks a day for many years increases the chance of developing cancers of the mouth, throat, oesophagus, stomach, liver, colon, lymphomas, prostate, kidney, breast and ovaries.¹

Consuming 2–3 alcoholic drinks a day is associated with a 20% higher risk of developing colorectal cancer, which increases to 40% at higher intakes.⁴ Some studies have shown that even one alcoholic drink a day (6–8 g of pure ethanol) raises the risk of breast cancer by 11%,² a sobering incentive to moderate intake.

Toxic overload

Environmental toxins are ubiquitous substances found in our everyday lives. Various cancers have been linked to environmental carcinogens (see Figure 2).⁹

Figure 2. Various cancer have been linked to environmental carcinogens.⁹

For example, endocrine-disrupting compounds (EDCs) such as dioxins and synthetic chemicals (e.g. bisphenol A (BPA), phthalates, and parabens) are highly persistent in the environment and bio-accumulative. Found in pesticides, plasticizers, pharmaceutical agents, personal care products, food products and packaging; certain EDCs have potential to elevate breast cancer risk.¹⁰ Evidence is accumulating to associate occupational exposure to persistent pesticides with prostate cancer.¹¹

Increasing patients’ awareness of potential environmental exposures is key. Educating them on practical steps that can be taken to minimise toxin exposure in their daily lives is an important element of adopting a healthy lifestyle.

Helping patients prioritise prevention

While genetics and a multitude of factors influence carcinogenic risk, one in three cancer cases can be prevented through healthy lifestyle choices.¹² This is empowering knowledge for all patients, especially those with predisposing genetic phenotypes or a family history of cancer.

Natural health practitioners play an important role in educating patients about potential risk factors and practical strategies to minimise them. Supporting the implementation of positive and protective lifestyle habits can help uplevel patient health now, with the potential to reduce risk of cancer in the future.

References

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2. Lewandowska AM, Rudzki M, Rudzki S, Lewandowski T, Laskowska B. Environmental risk factors for cancer - review paper. Ann Agric Environ Med. 2019 Mar 22;26(1):1-7. 

3. Tanaka Y, Shimizu S, Shirotani M, Yorozu K, Kitamura K, Oehorumu M, et al. Nutrition and cancer risk from the viewpoint of the intestinal microbiome. Nutrients. 2021 Sep 23;13(10):3326.

4. Lewandowska A, Rudzki G, Lewandowski T, Stryjkowska-Góra A, Rudzki S. Risk factors for the diagnosis of colorectal cancer. Cancer Control. 2022 Jan-Dec;29:10732748211056692.

5. Huang T, Yang B, Zheng J, Wahlqvist ML, Li D. Cardiovascular disease mortality and cancer incidence in vegetarians: a meta-analysis and systematic review. Ann Nutr Metab. 2012; 60(4): 233–240.

6. Crowe FL, Appleby PN, Travis RC, Key TJ. Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians: results from the EPIC-Oxford cohort study. Am J Clin Nutr. 2013; 97(3): 597–603.

7. Cancer Council. Move your body [Internet]. Australian Cancer Council. [cited 2023 June 22]. Available from: https://www.cancer.org.au/cancer-information/causes-and-prevention/diet-and-exercise/move-your-body 

8. Cancer Council Queensland. Harmful effects of smoking [Internet]. Cancer Council QLD; Brisbane, QLD. [cited 2023 Jan 22]. Available from: https://cancerqld.org.au/cancer-prevention/tobacco-smoking/

9. Anand P, Kunnumakkara AB, Sundaram C, Harikumar KB, Tharakan ST, Lai OS, et al. Cancer is a preventable disease that requires major lifestyle changes. Pharm Res. 2008 Sep;25(9):2097-116. 

10. Wan MLY, Co VA, El-Nezami H. Endocrine disrupting chemicals and breast cancer: a systematic review of epidemiological studies. Crit Rev Food Sci Nutr. 2022;62(24):6549-6576.

11. Kahn LG, Philippat C, Nakayama SF, Slama R, Trasande L. Endocrine-disrupting chemicals: implications for human health. Lancet Diabetes Endocrinol. 2020 Aug;8(8):703-718.

12. Cancer Council. Causes and prevention [Internet]. Australian Cancer Council. [cited 2023 June 22]. Available from: https://www.cancer.org.au/cancer-information/causes-and-prevention