Study Finds Relationship Between Glycemic Index and Lung Cancer Risk

Xifeng Wu, MD, PhD

Xifeng Wu, MD, PhD

Research has identified a correlation between a diet with a high glycemic index (GI) and an increased risk of developing lung cancer in non-Hispanic whites. The study found a nearly 50% higher risk in patients with the highest daily GI compared with those whose GI was lowest.

Accumulating evidence suggests that dietary factors may modulate lung cancer risk. The study, published in Cancer Epidemiology, Biomarkers & Prevention, is the largest to examine the relationship between GI and lung cancer and the first to examine this relationship in particular subgroups, including those who never smoked and those diagnosed with the squamous cell carcinoma (SCC) subtype of lung cancer.

GI is a measure of the quality of dietary carbohydrates, defined by how quickly blood sugar levels are raised following a meal. Glycemic load (GL), is a related measure of carbohydrate quantity.

“Diets high in glycemic index result in higher levels of blood glucose and insulin, which promote perturbations in the insulin-like growth factors (IGFs),” noted lead study author Stephanie Melkonian, a postdoctoral fellow at The University of Texas MD Anderson Cancer Center, in a statement. “Previous research suggests increased levels of IGFs are associated with increased lung cancer risk. However, the association between glycemic index and lung cancer risk was unclear.”

To further elucidate this relationship, the MD Anderson team surveyed nearly 1905 patients with newly diagnosed lung cancer and 2413 healthy individuals recruited from Kelsey-Seybold Clinics, a large physician group in the Houston area. Individuals reported their past dietary habits and health histories, including food frequency and portion size, through in-person interviews.

Participants were then divided into quintiles depending upon their answers. Those in the highest quintile of GI had a 49% increased risk of lung cancer versus those in the lowest quintile. Those in the highest quintile also had a 92% higher risk of developing SCC, but a less significant association was seen with developing adenocarcinoma.

Although tobacco use is the leading cause of lung cancer, among never-smokers in the highest quintile of GI, the researchers discovered that they were more than twice as likely to develop lung cancer as those in the lowest quintile. Among smokers, the risk was only elevated by 31% between the two groups.

GL was not associated with increased lung cancer risk for most patients, which the authors said suggests that it is the average quality, rather than quantity, of carbohydrates consumed which may impact lung cancer risk

The study also examined the impact of education, which is often related to socioeconomic status and has been linked with diet quality and smoking behaviors. Among participants with less than 12 years of education, those in the highest GI quintile had a 55% higher risk of developing lung cancer than those in the lowest quintile.

“Although smoking is a major, well-characterized risk factor for lung cancer, it does not account for all the variations in lung cancer risk,” said senior study author Xifeng Wu, MD, PhD, professor of epidemiology at MD Anderson, in a statement. “This study provides additional evidence that diet may independently and jointly with other risk factors impact lung cancer etiology.”

“Traditionally, glycemic index is only emphasized for diabetes prevention and management. However, if the results from this study are confirmed, healthcare providers should be made aware of the link between glycemic index and lung cancer, so they can communicate with their patients and the public about dietary changes for lung cancer prevention,” Wu continued.

Wu also noted that as a retrospective study, one limitation of the research is errors in participants’ recall and reporting of dietary intake; additionally, the study did not include information on whether participants had existing diabetes, hypertension, or heart disease.

The authors said that further research would be necessary to determine whether the association between GI and lung cancer carries over to other racial and ethnic groups.

Melkonian SC, Daniel CR, YeY, et al. Glycemic index, glycemic load, and lung cancer risk in non-Hispanic whites. Cancer Epidemiol Biomarkers Prev. 2016;25(3):532-539.