The belief that sugar consumption promotes cancer development and progression is based on the Warburg hypothesis, in which cancer cells preferably produce adenosine triphosphate (ATP) by glycolysis instead of oxidative phosphorylation.1 As a result, cancer cells have increased glucose uptake compared with normal cells.
No randomized, controlled trials have evaluated the direct effect of sugar consumption on cancer risk or progression, though several prospective cohort/case-control studies evaluated sugar intake directly or indirectly through dietary pattern, carbohydrate intake, and glycemic load.
Sugar Intake and Cancer Outcomes
The NIH-AARP prospective cohort study included 353,751 subjects aged 50 to 71 who completed a food frequency questionnaire and were followed for 13 years.2 The amount of added sugars, defined as sugars added at the table or as ingredients in prepared or processed foods, sucrose, and fructose, were determined.
Total sugar, added sugars, fructose, added fructose, sucrose, and added sucrose were not associated with cancer-related mortality among women or men, though total sugars (P <.0001 and .03, respectively) and fructose (P < .0001 and .002, respectively) were significantly associated with all-cause mortality among women and men.
An analysis of the CALGB 89803 trial of adjuvant chemotherapy for stage III colon cancer evaluated the effect of sugar-sweetened beverages on recurrence and mortality.3 Sugar-sweetened beverages were defined as 12 oz servings of sugar-sweetened sodas and other beverages, including fruit drinks and lemonade.
Consumption of at least 2 servings of sweetened-beverages per day was significantly associated with worse colon cancer–free survival (hazard ratio [HR], 1.67; 95% CI, 1.04-2.68; P = .02) and recurrence-free survival (HR, 1.84; 95% CI, 1.12-3.04; P = .02), but not overall survival, compared with the lowest intake of less than 2 servings per month. The association was stronger among patients who had a body mass index of 25 kg/m2 or more and those who were less physically active.
Sugar Intake and Cancer Risk
Another analysis of the NIH-AARP cohort demonstrated that high levels of total sugar intake were significantly associated with increased incidence of pleural cancer (HR, 2.64; 95% CI, 1.33-5.24; P = .006). Similarly, high levels of added sugars were associated with increased incidence of pleural cancer (HR, 2.90; 95% CI, 1.35-6.24; P = .03) and esophageal cancer (HR, 1.44; 95% CI, 1.03-2.03; P = .007).4
A protective effect, however, was associated with some types of sugar intake and other cancer types, such as higher levels of total sugar and oral cancer (HR 0.71; 95% CI, 0.54-0.93; P = .01), which may call into question the validity of these findings.