OPINION | Change your diet to change your cancer risk

• Modifiable risk factors are important for cancer prevention
• Following a healthy diet is a change you can make
• Research on cancer and diet is evolving daily

The number of people diagnosed with cancer are increasing each year, especially in developing countries such as South Africa. In 2020, 108 168 new cancer cases were diagnosed in South Africa compared to 56 785 cases in 2010.

This sketches a rather dark picture since the growing number of cancer cases lowers life expectancy of the population, contributes to financial strains on various public health care sectors, and affects more families on a financial and emotional level.

Cancer prevention is therefore considered to be of utmost importance.

Some factors can increase your cancer risk, for instance smoking of tobacco products, consuming alcohol, harmful exposure to sunlight and exposure to viruses/bacteria/parasites.

Other factors can decrease your cancer risk such as following a healthy diet, being active and maintaining a healthy body weight.

Some risk factors are modifiable, or can be changed, such as your diet, weight, physical activity, smoking and alcohol consumption while other factors such as genetic cancer susceptibility, reproductive factors and your age are non-modifiable. 

The question most people ask is how much of my cancer risk is due to modifiable risk factors – in other words – what is the percentage of my cancer risk that I can do something about? 

Modifiable risk factors are particularly important for cancer prevention. 

Current research shows that 30 to 50% of all cancers can be prevented by following a healthy diet, being active and maintaining a healthy body weight.

Considering the complexity of our daily diet and the link thereof with cancer, research in this field is evolving every day. While there are still many unanswered questions, it helps to look at the latest research that provides us with strong evidence.

There is currently strong evidence that consumption of red-and-processed meat (viennas, polony, russians, cold cuts etc.)  increases the risk for colorectal cancer while wholegrains, dairy and dietary fibre intake decrease the risk for colorectal cancer.

Non-starchy vegetables decrease the risk for throat cancer, while food preserved by salt are linked to stomach cancer. Growing evidence suggest that coffee protects against liver cancer while alcohol consumption is causative of seven different cancers.

International organisations such as the World Health Organisation, the World Cancer Research Fund, American Institute for Cancer Research and national organisations such as the Cancer Association of South Africa (CANSA) aim to prevent cancer by educating the public on lifestyle changes that can contribute to lower cancer risk.

Following a healthy diet, being active and maintaining a healthy body weight remain important and the most cost-effective ways to prevent several cancers.  The following set of recommendations based on diet, body weight, and activity can be followed to lower your cancer risk.

Cancer Prevention Recommendations:

• Be a healthy weight: Being overweight or obese can increase your risk of developing various cancers. A healthy weight can be determined by your Body Mass Index (BMI) (your weight in kg divided by the squared metre of your height in metre). The goal is to keep your weight as low as possible within the healthy BMI range (18.5 to 24.9) throughout life.

• Be physically active: Physical activity decreases your risk of developing cancer and it helps prevent excess weight gain. It is advised to limit inactive habits and to do at least 150 minutes of moderate exercise (walking fast or doing house chores) or 75 minutes of vigorous exercise (running or rope jumping) a week.

• Eat whole grains, vegetables, fruit and beans: It is recommended to consume at least 5 portions of fruit and vegetables (approximately 80 g/portion) and 30 g of fibre from beans, lentils and whole grain cereals, bread, pasta or rice, per day. Also, be sure to include a variety of foods in your daily diet.

• Limit fast foods and other highly processed foods high in fat, salt, starches or sugars: The intake of fast foods and highly processed foods such as heat-and-eat dishes, potato crisps, cakes, pastries, cookies and sweets increase the risk of weight gain and should therefore be limited.

• Limit red and processed meat: It is advised to limit red meat intake to no more than three portions per week (approximately 350 g to 500 g cooked weight per week) and to consume very little, if any, processed meat. However, you do not have to completely avoid eating red meat as it is a valuable source of various important nutrients.

• Limit sugar sweetened drinks: Consumption of sugar sweetened drinks may increase your risk of weight gain. It is advised to consume mostly water and unsweetened drinks. There is no strong evidence that artificial sweeteners found in low kilojoule soft drinks are a cause of cancer.

• Limit alcohol consumption: For cancer prevention, it is advised to strictly limit alcohol consumption as it is a cause of various cancers.

• Do not use supplements for cancer prevention: Consuming a variety of foods on a daily basis is more likely to protect against cancer than dietary supplements. High dose beta carotene supplements are linked to lung cancer.

• Breastfeed your baby, if you can: Breastfeeding reduces breast cancer risk for the mother, while being breastfed contributes to protect children against excess weight gain.

The Covid-19 pandemic reminded us how important prevention is and to take care of our health. This includes supporting our immune systems by following a healthy diet and lifestyle, not only to fight the Covid-19 virus, but also to combat and prevent several non-communicable diseases, such as cancer. 

You can find a Registered Dietitian in your area here.

*Inarie Jacobs is a registered dietitian, and Dr Christine Taljaard-Krugell is the president of the Association for Dietetics in South Africa