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Cancer is a generic term for a group of diseases that can affect essentially any part of the body. Other terms commonly used are malignant tumours and neoplasms. A defining feature of cancer is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other tissues and organs.

How common is cancer?

Cancer is a leading cause of death worldwide, accounting for ~10 million deaths in 2020. That year, the most common forms were:

  • breast (2.26 million deaths);
  • lung (2.21 million deaths); 
  • colon (large intestine) and rectum (1.93 million deaths);
  • prostate (1.41 million deaths); 
  • skin (non-melanoma) (1.20 million deaths); and
  • stomach (1.09 million deaths).

What causes cancer?

Cancer develops when normal cells are transformed into tumour cells in a multi-stage process that generally progresses from a pre-cancerous lesion to a malignant tumour. These changes are the result of the interaction between an individual’s genetic factors and three main categories of external agents, including (but not limited to):

  • physical carcinogens, such as ultraviolet and ionizing radiation;
  • chemical carcinogens, such as asbestos, components of tobacco smoke, alcohol, arsenic (a drinking water contaminant), and aflatoxin (a food contaminant); and
  • biological carcinogens, such as infections from certain viruses, bacteria, or parasites.

What are common risk factors for cancer?

Air pollution, tobacco use, alcohol consumption, physical inactivity and unhealthy diet are risk factors for cancer and other noncommunicable diseases like type 2 diabetes, heart disease and stroke.

What are the dietary risk factors?

As discussed in Food for Thought and What’s New?, it is not really feasible or ethical to conduct randomised controlled trials to determine dietary risk factors for most forms of cancers. However, evidence from observational studies have consistently found associations between nutritional factors and increased and decreased risk of cancer:

Factors that may increase risk

  • Excessive body fat and obesity
  • Excessive consumption of red (more than 455 g a week) and processed meat (treat as a special occasion food)
  • Excessive consumption of salt and salty foods (more than 2000 mg of sodium a day)
  • Excessive alcohol consumption (more than 3 Standard drinks a day) • Consuming mouldy peanuts or grains (may be contaminated with aflatoxin)

Factors that may decrease risk

  • Consuming at least 2 serves of fruit (2 x 150 grams (5.3 ounces)) a day
  • Consuming at least 5 serves of non-starchy vegetables (5 x 75 grams (2.65 ounces)) a day
  • Consuming 4-6 serves (500 kJ or 120 Calorie portions) of grainy foods (preferably wholegrain and lower GI) a day
  • Consuming seafood at least twice per week, preferably fatty fish (mackerel, herring, salmon, sardines, etc…)
  • Consuming 2-3 serves of dairy foods (a serve = 1 Cup milk; ¾ cup yoghurt; 2 slices cheese) and/or alternatives a day

The astute reader will realise that these dietary recommendations for reducing the risk of cancer are in-line with international Dietary Guidelines for general health and wellbeing.

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Dr Alan Barclay, PhD, is a consultant dietitian and chef with a particular interest in carbohydrates and diabetes. He is author of Reversing Diabetes (Murdoch Books), and co-author of nearly 40 scientific publications, The Good Carbs Cookbook (Murdoch Books), Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment Publishing).
Contact: Follow him on Twitter, LinkedIn or check out his website.