Sugary drinks and the pathway towards cancer

cup-of-coffeeMessages from the media on sugary drinks are conflicting.  On one hand, the notion of a seasonal pumpkin-flavored latte evokes sentiments of childhood traditions. On the other, news reports of a rising obesity epidemic, ridden by the life altering and debilitating effects of chronic diseases cast a threatening shadow over our comfort drinks.

In recognition of World Obesity Day on October 11th, the World Health Organization (WHO) engaged governments worldwide to adopt a tax on sugary beverages, which includes soft drinks, sports drinks, and fruit juices. The WHO argued that lowering sugary beverage consumption also lowers refined sugar consumption, which can curb chronic disease onset in populations and relieve avoidable government health service expenditures.

The WHO recommends limiting sugar consumption to 10 percent or less of total energy intake. For a person of healthy body weight consuming 2000 calories per day, 10% would equal 50 grams of sugar or less daily. As it stands, the average in many countries including the UK and Portugal, exceed recommended values, with people consuming 12 to 25%. These proportions vary even within countries and among various regions, for a range of cultural and economic reasons.

The WHO cites strong evidence that sugary drink consumption is associated with increased weight gain and obesity [1, 2]. Sugary drinks contain a large amount of excess calories and refined sugars that directly enter the blood stream without the modulating effect of fibers or fat naturally present in whole foods. Once refined sugars enter the blood, an insulin spike, in addition to other hormonal responses, are triggered to control blood sugar levels.

Studies have shown that consistent consumption of sugary drinks over time, increases the risk of insulin resistance, hyperglycemia, and ultimately, diabetes [3, 4].

However, the leap from sugary drinks to diabetes-related cancers has yet to be established. The problem is two-fold. One problem lies in how researchers measure and quantify sugary drink consumption. How can we know, for certain, how much sugar people consume from drinks? Secondly, the gap between sugary drink consumption and cancer occurrence may be too large a leap to bridge. We know that sugary beverages are on the roadmap to cancer development through their contribution to obesity and diabetes, but it is not clear whether the sugary beverages cause cancer development directly or whether metabolic dysregulation resulting from sugary beverage consumption is the causal factor.

Traditional methods for assessing dietary consumption include food diaries and food frequency questionnaires. Food diaries contain day-by-day eating habits recorded by the patient, but are subject to increased intake awareness and thus possible deviation from usual dietary habits. Food frequency questionnaires are useful in assessing a cumulative or habitual dietary intake, such as frequency of fish consumed per week, but may not be helpful in identifying unhealthily prepared foods in each food category. Both of these self-assessed methods also rely on patient recall, which may or may not be accurate.

Accurate or not, dietary habits are not the only part of the equation when it comes to cancer risk. A person’s own metabolic type may play a role in cancer risk. A recently published European Prospective Investigation into Cancer and Nutrition (EPIC) study divided individuals based on metabolic types that included two parameters: body size measured by BMI or waist circumference and high insulin measured by C-peptide from blood samples [5]. Individuals who were overweight or obese but had normal insulin levels were at lower risk for colorectal cancer than those who were normal weight but had abnormally high insulin levels. This study showed metabolic dysregulation, rather than body size, may be the real culprit for higher colorectal cancer risk.

There remains much work to be done regarding whether and to what extent sugary beverages contribute to some cancers. We know that not all individuals consuming sugary beverages have the same susceptibility to cancer. Individual genetics and metabolic type may modify the effects of sugar on cancer risk. The timing from sugary drink consumption to cancer occurrence and whether the association is linear are still unknown. We also don’t know the exact biological mechanism of how metabolic dysregulation and hyperinsulinemic states actually lead to cancer. However, studies using genetic proxies or blood marker levels hold the promise to objectively identify modifiable lifestyle traits related to diabetes-related cancers. These studies also underscore the ability to pin down cancer risk traits in terms of measurable biomarkers, exposing targets to prevent and possibly treat diabetes-related cancers before they occur in the first place.

A wide discrepancy remains between WHO sugar intake recommendations and actual dietary practices. There is perhaps a no more gripping or relevant reason to limit sugary drink consumption, than if it increases risk of cancer as well as diabetes and chronic disease. It is a link that has yet to be clearly defined, and highlights the need for further research to direct cancer prevention strategies.

 

References:

  1. Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ. 2013; 346:e7492.
  2. Malik VS, Pan A, Willett WC, Hu FB. Sugar-sweetened beverages and weight gain in children and adults: a systematic review and meta-analysis. American Journal of Clinical Nutrition. 2013; 98(4):1084-102.
  3. Singh GM, Micha R, Khatibzadeh S, et al. Estimated global, regional, and national disease burdens related to sugar-sweetened beverage consumption in 2010. Circulation 2015 Aug 25;132(8):639-66. doi: 10.1161/CIRCULATIONAHA.114.010636.
  4. Schulze MB, Manson JE, Ludwig DS, et al. Sugar-sweetened beverages, weight gain, and incidence of type 2 diabetes in young and middle-aged women. JAMA2004 ;292 :927 –34.
  5. Murphy N, Cross AJ, Abubakar M, Jenab M, Aleksandrovna K, Boutron-Ruault MC, et al. A Nested Case-Control Study of Metabolically Defined Body Size Phenotypes and Risk of Colorectal Cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC). Plos Med. 2016 Apr 5;13(4):e1001988. doi: 10.1371/journal.pmed.1001988.
Dana Hashim

Dana Hashim

Dana Hashim is a visiting scientist of the Genetics Section at IARC, and is collaborating in EPIC studies.  Her research focuses on identifying modifiable risk factors involved in cancers and preventing or reducing carcinogenic exposure circumstances.

Research Interests: Cancer etiology and prevention
Dana Hashim

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2 comments to Sugary drinks and the pathway towards cancer

  • Rola Pacha

    Excellent !

  • Mamoun Pacha,MD

    There is no doubt that sugary drinks is serious health issue and reason for obesity and diabetes.however the relationship between sugar and cancer is very intriguing .
    We need further studies. This is very important subject. I wish you a good luck

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