Dietary Glycemic Index Linked to Lung Cancer Risk in Non-Hispanic White Populations
Consuming a diet with a high glycemic index was independently associated with an increased risk of developing lung cancer in non-Hispanic whites, according to a new epidemiologic study from The University of Texas MD Anderson Cancer Center.
This research, published by Melkonian et al in Cancer Epidemiology, Biomarkers & Prevention, represents the largest study to investigate potential links between glycemic index and lung cancer. The findings also unveil for the first time that glycemic index was more significantly associated with lung cancer risk in particular subgroups, such as never-smokers and those diagnosed with the squamous cell carcinoma subtype of lung cancer.
Accumulating evidence suggests that dietary factors may modulate lung cancer risk, explained Xifeng Wu, MD, PhD, Professor of Epidemiology at MD Anderson. Diets high in fruits and vegetables may decrease risk, while increased consumption of red meat, saturated fats, and dairy products have been shown to increase lung cancer risk.
Glycemic index is a measure of the quality of dietary carbohydrates, defined by how quickly blood sugar levels are raised following a meal. Previous studies have investigated associations between glycemic index and glycemic load, a related measure of carbohydrate quantity, and risk of numerous other cancers.
“Diets high in glycemic index result in higher levels of blood glucose and insulin, which promote perturbations in the insulin-like growth factors,” said Stephanie Melkonian, postdoctoral fellow with Dr. Wu’s team. “Previous research suggests increased levels of insulin-like growth factors are associated with increased lung cancer risk. However, the association between glycemic index and lung cancer risk was unclear.”
To clarify the associations between glycemic index, glycemic load, and lung cancer risk, the researchers surveyed 1,905 MD Anderson patients newly diagnosed with lung cancer and 2,413 healthy individuals recruited from Kelsey-Seybold clinics. Participants self-reported past dietary habits and health histories. Dietary glycemic index and glycemic load was determined using published food glycemic index values, and subjects were divided into five equal groups, based on their glycemic index and glycemic load values.
Study Findings
“We observed a 49% increased risk of lung cancer among subjects with the highest daily glycemic index compared to those with the lowest daily glycemic index,” said Dr. Wu. “The associations were more pronounced among subjects who were never-smokers, diagnosed with squamous cell carcinoma, or had less than 12 years of education.”
Interestingly, glycemic load had no significant associations with lung cancer risk. “This suggests that it is the average quality, instead of quantity, of carbohydrates consumed that may modulate lung cancer risk,” said Dr. Wu.
When investigating never-smokers in the study, the researchers found that those in the highest glycemic index group were more than twice as likely to develop lung cancer as those in the lowest group. Among smokers, the risk was only elevated by 31% between the two groups. The relatively mild effects of a risk factor such as glycemic index are more evident in the absence of the dominant risk factor, explained Dr. Wu.
The researchers also noted stronger associations in those diagnosed with squamous cell carcinoma and those with lower educational levels. Participants in the highest glycemic index group were 92% more likely to develop the squamous cell carcinoma subtype compared to the lowest glycemic index group, possibly due to the influence of elevated insulin-like growth factors on squamous cell carcinoma development.
Among those with fewer than 12 years of education, subjects in the highest glycemic index group were 77% more likely to develop lung cancer than those in the lowest glycemic index group. This contrasts with an elevated risk of only 33% in subjects with more than 12 years of education.
The authors note that educational level is a proxy for socioeconomic status, which has been linked with diet quality and smoking behaviors.
While specific dietary recommendations cannot be made on the basis of these results, the authors suggest limiting foods and beverages with high glycemic index (such as white bread or bagels, corn flakes and puffed rice), for a more balanced diet and to lower the risk for lung cancer and chronic diseases. Examples of low glycemic index foods include whole-wheat or pumpernickel bread, rolled or steel-cut oatmeal, and pasta.
“The results from this study suggest that, besides maintaining healthy lifestyles, such as avoiding tobacco, limiting alcohol consumption, and being physically active, reducing the consumption of foods and beverages with high glycemic index may serve as a means to lower the risk of lung cancer,” said Dr. Wu.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
