*Content has been reviewed by Dr. Kelly A, Meckling (Human Health & Nutritional Sciences, University of Guelph)

There are more than 200 different types of cancer. All cancers share common traits, which include uncontrolled growth and division of abnormal cells (1, 2).

  • Risk Factors for Developing Cancer and Reducing Cancer Risk. Genetics is the primary non-modifiable risk factor for cancer development. The World Cancer Research Fund also identifies lifestyle factors such as smoking, alcohol intake, diet, and physical activity, among others, as risk factors for cancer development.
  • Sugars and Cancer. Recent meta-analyses and systematic reviews of prospective cohort studies indicate that there is no direct causal link between consumption of sugars (no matter the quantity or type) and the risk of cancer. However, there is an association between overweight and obesity and the risk of some types of cancers (e.g. pancreatic, colorectal, post-menopausal breast, etc.). Consuming excessive calories (including calories from sugars) can increase the risk of overweight and obesity.
  • Sugars in the Diets of Individuals with Cancer. Dietary recommendations about sugars for individuals with cancer are not different from recommendations for individuals without cancer.

Risk Factors for Developing Cancer

There are several factors that increase the risk of developing cancer. One of the most important non-modifiable causes of cancer are a person’s genetics. There are genes in each cell in the body, and sometimes changes to the way these genes work can cause tumors to grow. The National Cancer Institute and Canadian Cancer Society (3, 4) identify the following risk factors for cancer:

Non-modifiable risk factors Modifiable risk factors
  • Age
  • Cancer-causing substances that may be in the air or drinking water (e.g. arsenic, formaldehyde)
  • Having a condition that suppresses the immune system
  • Chronic inflammation
  • Hormone levels 
  • Consuming excess alcohol
  • Smoking
  • Having an unhealthy diet
  • Low levels of physical activity
  • Having overweight or obesity 
  • Radiation coming from the sun's ultaviolet rays, or other types of radiation (e.g. radon, X-rays)

Reducing Cancer Risk

A recent report from the World Cancer Research Fund highlights a strong link between having overweight or obesity and an increased risk for ten cancers: bowel (colorectal); gallbladder; kidney; liver; oesophagus; ovary; pancreas; prostate (advanced); post-menopausal breast and womb (endometrial) (2).

One lifestyle factor that can contribute to overweight and obesity is consuming excess Calories compared to the amount required on a daily basis for normal body functions, movement, and physical activity.

To reduce risk of cancer, the World Cancer Research Fund (5, 6) encourages individuals to eat a healthy and balanced diet, control calorie intake and be physically active (see image below). The overall recommendations from the World Cancer Research Fund to maintain a healthy body weight are summarized, and shown in the figure below:

  • Eating a diet rich in wholegrains, vegetables, fruit, and pulses such as beans
  • Limiting consumption of “fast foods” and other processed foods high in fat, starches or sugars (many pre-prepared dishes, snacks, bakery foods and desserts, and confectionery (candy))
  • Drinking mostly water and limiting consumption of sugars-sweetened drinks
  • Being physically active

World Cancer Research Fund's cancer prevention recommendations

Source: Recommendations for cancer prevention. World Cancer Research Fund 2018 (5).

Sugars and Cancer

Does consuming sugars feed the growth of cancer cells? From a physiological perspective, every cell in the body uses sugars in the form of glucose as a source of energy (2). The body has very good control over the changes in blood glucose levels in response to dietary intakes of carbohydrates (including sugars); however, blood glucose levels are not determined by the dietary intake of sugars. There is a lack of evidence to support the theory that dietary sugars directly feed cancer development or cancer progression, or the notion that limiting sugars intake can “starve” cancer cells or impact outcomes (1).

To date, there is no evidence of a direct causal link between sugars consumption and cancer occurrence (5). Systematic reviews and meta-analyses have assessed data from studies looking at the relationship between dietary sugars intake and cancer occurrence. For example:

  • A systematic review summarized data from 37 prospective cohort studies. Most studies indicated a null association between cancer and sugars, although some studies reported a suggestive detrimental association between added sugars, sugars-sweetened beverages and cancer occurrence (7).
  • Another systematic review and meta-analysis reported that when the totality of evidence was assessed, there was no association between sugars-sweetened beverages and colorectal cancer. However, there were three studies that did report an association between sugars-sweetened beverage intake and colorectal cancer (8).

Based on these studies, it is possible that there may be an indirect link between sugars and cancer, i.e. foods higher in calories may be higher in sugars à consuming high calorie foods on a regular basis may lead to weight gain à weight gain is associated with an increased risk for some types of cancers (9).

In addition to Calories, the presence of other factors including micronutrients and fibres in sugars-containing foods may also influence the association with cancer risk. Dietary fibres and certain micronutrients such as folate, vitamin C, selenium and carotenoids have been shown to be protective against cancer development (10).

Sugars in the Diets of Individuals with Cancer 

The idea that “sugar feeds cancer” is a common misconception in the media. Sugars per se do not have a direct link to cancer. Sugars in the diet come in many forms including naturally occurring sources like fruits and added sugars like whole-grain cereals, some of which are higher in nutrients and lower in Calories. To the body, and to the cells in our body, once these foods are broken down, the glucose components are the same no matter the original food source (11). Dietary recommendations about sugars for individuals with cancer are not different from recommendations for individuals without cancer (11).  

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References

  1. Cancer Research UK: What is cancer? and Cancer Research UK: Sugars and cancer – what you need to know; Accessed: August and December 2018.
  2. World Health Organization: Cancer. Last updated: 2018; Accessed: August 2018.
  3. National Cancer Institute: Risk Factors for cancer. Last updated: 2015; Accessed August 2018.
  4. Canadian Cancer Society. Last updated: 2018; Accessed September 2018.
  5. World Cancer Research Fund and the American Institute for Cancer Research: Diet, Nutrition, Physical Activity and Cancer: A Global Perspective. 2018.
  6. World Cancer Research Fund: Curbing Sugar Consumption. 2015.
  7. Makarem N, Bandera EV, Nicholson JM, Parekh N. Consumption of Sugars, Sugary Foods, and Sugary Beverages in Relation to Cancer Risk: A Systematic Review of Longitudinal Studies. Annual review of nutrition. 2018 May 25(0).
  8. Schwingshackl L, Schwedhelm C, Hoffmann G, Knüppel S, Laure Preterre A, Iqbal K, Bechthold A, De Henauw S, Michels N, Devleesschauwer B, Boeing H. Food groups and risk of colorectal cancer. International journal of cancer. 2018 May 1;142(9):1748-58.
  9. Canadian Cancer Society: sugars and cancer. Last updated: 2018; Accessed September 2018.
  10. Willett WC. Micronutrients and Cancer risk. Am J Clin Nutr. 1994;59:1162S-1165S.
  11. British Columbia Cancer Agency: sugars and cancer. Last updated: 2015; Accessed September 2018.