Genes not only influence our eye colour, body shape and height, but can influence our cancer risk¹, too. Just how much of a role do our genes play in getting cancer?

What are Genes?

DNA (deoxyribonucleic acid) is the genetic material that our body is made of.

We get half of our DNA from our mothers and the other half from our fathers. Our DNA includes all the instructions needed for the body cells to function optimally.

Each human cell has about 25 000 genes. Genes are made up of long stretches of this DNA.

Simply put, DNA is like the alphabet and genes are the words that the DNA alphabet spells out. These genetic “words” (collectively known as the human genome²) spell out the body’s complete list of instructions to tell the cell what to do and when to grow and divide.

Each gene is made up of a specific DNA sequence that contains the instructions to make various proteins, each of which has a specific job or function in the body.

What Causes Cancer?

Cancer begins when the genes in a cell become abnormal (mutate )⁴ and the cell starts to grow and divide out of control. Mutations are abnormal changes in the DNA of a gene.

Mutations in a gene can affect how it functions.³ For example, a mutation might stop a gene from working completely, or it might keep a gene turned on, even if not needed.

The mutations may affect different genes that control cell growth and division. Some of these genes are called tumour suppressor genes.

Mutations may also cause some normal genes to become cancer-causing genes (known as oncogenes).

Is Cancer Genetic?

It takes more than one mutation in a cell for cancer to occur.

When someone has inherited an abnormal copy of a gene, though, their cells already start out with one mutation. This makes it all the easier (and quicker) for enough mutations to build up for a cell to become cancer.

That is why cancers that are inherited tend to occur earlier in life than cancers of the same type that are not inherited.

Even if you were born with healthy genes, some of them can become changed (mutated) over the course of your life. These acquired mutations are usually from exposure to various cancer-causing factors⁵ in our environment, such as radiation, excessive sunlight, cigarette smoke, hormones, and even our diet.

Other mutations have no clear cause and seem to occur randomly as the cells divide.

Taken together, this means that cancer is a genetic disease⁵. In general, cancer cells have more genetic changes than normal cells.

But each person’s cancer has a unique combination of genetic alterations. Some cancers that can be hereditary⁴ are breast cancer and ovarian cancer (linked to the BRCA1 and BRCA2 genes)

Are There Any Non-Genetic Factors That Affect Cancer?

Because genes are inherited, this means some types of cancer may cluster in families.

This is also due to the fact that certain behaviours and exposures, like smoking or obesity, cluster in families.

Yet most cancers are not linked to the genes we inherit from our parents. In fact, it is believed that only 5 – 10% of all cancers have a genetic link.⁶

People who inherit gene mutations may have a higher than average risk of developing some types of cancer, though it does not mean they will definitely get cancer.

Our diet and lifestyle play a large role in cancer development. It is estimated that one in three of the most common cancers that could be prevented through diet⁷ (as well as weight management and physical activity).

Scientists have outlined a few key cancer protective behaviours that we can all focus on each day.

Now while we may get the luck of the drawer when it comes to our genetic risk of cancer, it is good to know that there are some things that are within our control for cancer prevention:

Be a Healthy Weight.⁸ Being overweight increases the risk of cancers⁸ of the bowel, breast, gallbladder, liver, kidney, stomach, and oesophagus. Studies have shown that as much as 1 in 5 of all cancer deaths⁹ may be related to excess weight. It is estimated that by 2030, obesity-related cancers will have the highest death rates⁹ of all the cancers. Avoid eating high energy foods¹⁰ and sugary drinks¹¹.
Enjoy More Grains, Vegetables, Fruit, and Beans.¹² Without a doubt, eating more fruit, vegetables and fibre is associated with reduced risk of cancer.¹³ Not only are these foods low in energy, but fruit, vegetables grains and beans are also rich in anti-cancer nutrients like phytochemicals (e.g. carotenoids, phenolic compounds), vitamin C, vitamin E, minerals, fibre, and other bioactive compounds. And it is a double-win for fruit and vegetables as the cancer-protective properties is likely not only because of these nutrient compounds but also because of other dietary factors within the fruit and vegetables as a whole food, like fibre. For cancer prevention, aim for at least five portions (400 g) of a variety of vegetables and fruit daily. Choose a different coloured fruit and/or vegetable for a different cancer-protective nutrient each day.
Limit Red Meat and Avoided Processed Meat.¹⁴ As many as 34 000 cancer deaths.¹⁵ are attributed to diets high in processed meat each year. Did you know that for every 50g of processed meat eaten each day you increase your cancer risk by 18%?¹⁶ This is the same as roughly 4 slices of ham, a small, closed handful of biltong, or one hot dog. For this reason, the World Cancer Research Fund recommends that less than 350g – 500 g of red meat is eaten per week.¹⁷, and very little, if any, processed meat.

Limiting/avoiding alcohol.¹⁸ and being more active.¹⁹ are also strongly recommended in our goal to prevent cancer.

While there might be a genetic link to cancer, this is only one piece of the larger, very complex puzzle of cancer: we still need to take actionable steps to manage our risk. We should not overemphasise that cancer is only a genetic disease.

While genes may play a role in cancer development, we know that there are other non-genetic factors that are just as important.

We must recognise that the causes of cancer are multifactorial and multidimensional.

The FitChef Difference

Our FitChef meals are proudly supportive of managing our cancer risk:

Portion controlled to manage energy intake.
High in fibre from wholegrains like wholewheat pasta, brown rice, and quinoa, as well legumes.
High in fruits and vegetables.
Unprocessed whole food, free from added preservatives and flavourants.
Low in added sugar and refined carbohydrates.

References

Pomerantz MM, Freedman ML. The Genetics of Cancer Risk. Cancer Journal. 2011;17(6):416-422.
National Human Genome Research Institute. The Human Genome Project. Accessed 6 July 2021. Available from: https://www.genome.gov/human-genome-project/
National Cancer Institute. The Genetics of Cancer. Accessed 2 July 2021. Available from: https://www.cancer.gov/about-cancer/causes-prevention/genetics
American Cancer Society. Family Cancer Syndromes. Accessed 2 July 2021. Available from: https://www.cancer.org/cancer/cancer-causes/genetics/family-cancer-syndromes.html
American Cancer Society. Genetics and Cancer. Accessed 2 July 2021. Available from: https://www.cancer.org/cancer/cancer-causes/genetics.html
World Cancer Research Fund. Inherited genes, family history, and cancer risk. Accessed 2 July 2021. Available from: https://www.wcrf-uk.org/uk/preventing-cancer/what-can-increase-your-risk-cancer/inherited-genes-family-history-and-cancer/
World Cancer Research Fund/ American Institute for Cancer Research. Food, nutrition, and the prevention of cancer: a global perspective. Washing DC; American Institute for Cancer Research. 2007
Word Cancer Research Fund/ American Institute for Cancer Research Continuous Update Project Export Report 2018. Body Fatness and Weight Gain and the Risk of Cancer. Available at http://www.dietandcancerreport.org.
Font-Burgada J, Sun B, Karin M. Obesity and cancer: the oil that feeds the flame. Cell Met Rev. 2016; http://dx.doi.org/10.1016/j.cmet.2015.12.015.
World Cancer Research Fund. Preventing Cancer. Cancer prevention recommendations- High-calorie foods and cancer prevention. Accessed 2 July 2021. Available from: https://www.wcrf-uk.org/uk/preventing-cancer/cancer-prevention-recommendations/avoid-high-calorie-foods.
World Cancer Research Fund. Preventing Cancer. Cancer prevention recommendations- Limit sugar-sweetened drinks. Accessed 2 July 2021. Available from: https://www.wcrf-uk.org/uk/preventing-cancer/cancer-prevention-recommendations/limit-sugar-sweetened-drinks
Word Cancer Research Fund/ American Institute for Cancer Research Continuous Update Project Export Report 2018. Wholegrains, vegetables and fruit and the risk of cancer. Available at https://www.wcrf.org/wp-content/uploads/2020/12/Wholegrains-veg-and-fruit.pdf.
Bradbury KE, Appleby PN, Key TJ. Fruit, vegetable, and fibre intake in relation to cancer risk: findings from the European Perspective Investigation into Cancer and Nutrition (EPIC). Am J Clin Nutr.2014;100(Suppl):394S-8S.
Bouvard V et al. Carcinogenicity of consumption of red and processed meat . Lancet Oncology. 2015;16:1600-1601.
Global Burden of Disease Cancer Collaboration. Global, regional, and national cancer incidence, mortality, years of life lost, years lived with disability, and disability-adjusted life-years for 32 cancer groups, 1990 to 2015. A systematic analysis for the global burden of disease study. JAMA Oncol. 2017. Published online December 3, 2016; doi:10.1001/jamaoncol.2016.5688.
International Agency for Research on Cancer. Consumption of red meat and processed meat. IARC Working Group, 2015. Available from: https://www.iarc.who.int/wp-content/uploads/2018/07/pr240_E.pdf
World Cancer Research Fund. Recommendations – limit red and processed meat. Accessed 2 July 2021. Available from: https://www.wcrf.org/dietandcancer/limit-red-and-processed-meat/
Word Cancer Research Fund/ American Institute for Cancer Research Continuous Update Project Export Report 2018. Alcoholic drinks and the risk of cancer. Available at http://www.dietandcancerreport.org.
Word Cancer Research Fund/ American Institute for Cancer Research Continuous Update Project Export Report 2018. Physical Activity and the Risk of Cancer. Available at http://www.dietandcancerreport.org.