May 16, 2016

Processed sugar intake and cancer risk: the evidence

It is undoubtedly concerning how many ways sugar can potentially cause or aggravate cancer either directly or indirectly. Despite this information, however, cynics argue that as there is a lack randomised controlled trials (RCTs), it cannot be proven that sugar actually harms humans.

It is true that RCTs are the “gold standard” evidence, but not everything can be assessed in this design – imaging trying to persuade two large groups to, at the throw of a dice, either eat a high sugar diet or no sugar at all to find out if the cancer risk is different several years later. Likewise, envisage asking people living with cancer to be randomised to a high sugar diet or not to see if it affects the cure rate. In both scenarios, people will simply eat what they want after the first few weeks, making any results meaningless.

Despite the deficit in RCTs, there are still an enormous amount of reliable data from what are known as prospective cohort studies. These involve following large populations for several years, whilst measuring their lifestyle habits and recording any diseases. Examples of the most prominent are summarised here:

  • A combined analysis of the Nurses’ Health Study and the Health Professionals Follow-up Study provided data on 100,000 participants for up to 20 years. The 1,809 people who developed colorectal cancer had a history of higher intake of processed carbohydrates, sucrose and fructose compared to people without cancer. The effect of these foods with a high glycaemic index (GI) and high glycaemic load (GL) was worse in men who were overweight [Michaud 2005].
  • A cohort study from Iowa (USA), evaluated 35,215 women for 10 years. The 212 cases of colon cancer had a higher intake of sucrose-containing foods and beverages other than ice cream/milk products. Again this risk was worse in those with overweight and curiously people who were tall [Sellers].
  • A further analysis of the Nurses’ Health Study identified 180 case of pancreatic cancer. Of note, women who were overweight and sedentary with a habit of eating meals with a high GL had a 53% increased risk [Michaud 2002].
  • A study from University of Minnesota looked at the dietary habits of more than 60,000 adults from Singapore for 14 years. They reported that drinking two or more sugary soft drinks a week nearly doubled the risk of developing any cancer and increased risk of pancreatic cancer by 87% [Mueller].

Michaud D and Liu et al. Dietary Sugar, Glycemic Load, and Pancreatic Cancer Risk in a Prospective Study. JNCI J Natl Cancer Inst. 2002; 94 (17): 1293-1300.
Michaud D et al. Sugar, and Colorectal Cancer Risk in Men and Women Cancer. Epidemiol Biomarkers Prev. January 2005; 14; 138.
Mueller NT et al. Soft drink and juice consumption and risk of pancreatic cancer: the Singapore Chinese Health Study. Cancer Epidemiol Biomarkers Prev. 2010 Feb;19(2):447-55. doi: 10.1158/1055-9965.EPI-09-0862.
Sellers T et al. Sugar, meat, and fat intake, and non-dietary risk factors for colon cancer incidence in Iowa women. Cancer Causes & Control. 1994; 5 (1), pp38-52.


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