Genes, nutrition and cancer

Annica Rust helps us understand how what we eat and its interaction with our genes (personalised DNA) can cause or prevent cancer.

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Cancer is a multi-factorial disease with modifiable and non-modifiable risk factors that play a role in its development. Non-modifiable risk factors include gender, age, ethnicity and a genetic predisposition. Modifiable risk factors are related to the environment and lifestyle, such as a poor nutritional intake, smoking, inactivity, poor sleeping habits, stress and obesity. These all play a role in the development of the disease. 

Nutritional genomics focuses on the diet and lifestyle-related diseases that are caused by interactions between the genome (genetic material/DNA) and environmental factors. 

Nutrigenetics and nutrigenomics fall under the umbrella of nutritional genomics¹. Nutrigenetics is how an individual’s genetic variation will affect function¹. Nutrigenomics is the interaction between genes and dietary components that will cause a change in gene expression¹. 

Most of your genes will have small sequence differences known as single nucleotide polymorphisms (SNPs). The SNPs may vary amongst individuals. A gene can be seen as a recipe to make a protein in your body. 

Proteins are important to regulate functions in your body and serve as building blocks for tissues. The genetic polymorphisms can cause a variation in metabolic responses to dietary components which can be cancer causing (carcinogenic) or cancer preventing². 

Dietary components can also modify the carcinogenic process by modifying cellular host defence, cell signalling pathways, cell differentiation and tumour growth.

Dietary components classified as cancer enhancers:

• Nitrates, a preservative in processed meat, can be reduced to nitrites which interact with amines/amides to form carcinogenic n-nitriso compounds, also known as nitrosamines¹.
• High salt intake is also seen as carcinogenic¹.
• Diets high in saturated fats often found in fat of red meat, chicken skin and baked products¹.
• Polycyclic aromatic hydrocarbons that form on the surface of meat products when it is grilled at high temperatures¹.
• High tobacco and alcohol intake are associated with an increased cancer risk¹. 
• A high intake of refined carbohydrates. It’s often products made with white flour that are low in fibre and high in sugar¹.

Dietary components classified as cancer inhibitors:

• Antioxidants, such as vitamin C, vitamin A, carotenoids, vitamin E, selenium and zinc as shown in table 1¹.
• Phytochemicals are the biological active components of plants, such as lycopene, anthocyanins, polyphenols, alpha- and beta-carotene, flavonoids, lutein and allyl sulphides. The food sources are indicated in table 2¹.

Table 1: Antioxidants with a cancer protective effect
Antioxidants	Food sources
Vitamin C	Brussels sprouts, broccoli, peppers, tomatoes, strawberries, orange and kiwifruit.
Vitamin A and carotenoids	Liver, cheese, milk, egg yolk, spinach, kale, apricots, papaya and mango.
Vitamin E	Sunflower seeds, hazelnuts, peanuts, spinach, broccoli, kiwifruit and egg.
Selenium	Brazil nuts, beef, chicken, tuna and milk.
Zinc	Beef, chicken, pork, baked beans and mixed nuts.

Table 2: Phytochemicals with a cancer protective effect
Colour	Phytochemicals	Fruits & vegetables
Red	Lycopene	Tomatoes, grapefruit  and watermelon.
Red and purple	Anthocyanins  and polyphenols	Berries, grapes, red wine  and plums.
Orange	Alpha- and beta-carotene	Carrots, mangos and pumpkin.
Orange and yellow	Flavonoids	Peaches, oranges, papaya  and nectarines.
Yellow and green	Lutein and zeaxanthin	Spinach, avocado, honeydew and asparagus.
Green	Sulforaphanes  and indoles	Cabbage, broccoli, Brussels sprouts and cauliflower.
White and green	Allyl sulphides	Leek, onion, garlic and chives.

Dietary components which are cancer enhancers and inhibitors for the general population are well defined by world health authorities, such as American Cancer Society, American Institute for Cancer Research and World Health Organisation. 

Nutrigenomics or personalised nutrition provides more individualised nutritional advice based on your genetic profile. Although nutrigenomics can be used to give personalised nutritional advice, it is important to bear in mind that nutrigenomics is a relatively new field, where only the tip of the iceberg is known. It is a field that holds the potential for new findings in the future.

References

1. Hamilton, K.K. & Grant, B.L. 2017. Nutrition in the life cycle. In Mahan, L.K., Escott-Stump, S., & Raymond, J.L. (eds). Krause’s food and the nutrition care process. 14th ed. St Louis. MO: Elsevier Saunders.
2. Gaboon, N.E.A. 2011. Nutritional genomics and personalized diet. Ain Shams University: The Egyptian Journal of Medical Human Genetics.12(1):1-7.
3. Elsamanoudy, A.Z., Neamat-Allan, M.A.M., Mohammad, F.A.H., Hassanien, M., Nada, H.A. The role of nutrition related genes and nutrigenetics in understanding the pathogenesis of cancer.