Consuming a diet with a high glycemic index, a classification of how rapidly carbohydrates elevate blood sugar levels, was independently associated with an increased risk of developing lung cancer in non-Hispanic whites, according to a new epidemiologic study from MD Anderson Cancer Center.
This research, published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, represents the largest study to investigate potential links between glycemic index (GI) and lung cancer. The findings also unveil for the first time that GI was more significantly associated with lung cancer risk in particular subgroups, such as “never smokers” — people who’ve never smoked or who’ve not smoked more than 100 cigarettes in their lifetime — and those diagnosed with the squamous cell carcinoma (SCC) subtype of lung cancer.
Nationally, lung cancer is the second most common cancer in both men and women, but is by far the leading cause of cancer mortality, with over 150,000 deaths from the disease expected in the U.S. in 2016, according to the American Cancer Society. While tobacco use is the leading cause of lung cancer, it fails to account for all cases, particularly in those who’ve never smoked.
Accumulating evidence suggests that dietary factors may modulate lung cancer risk, explained Xifeng Wu, M.D., Ph.D., professor of Epidemiology and senior author of the study. 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 GI and glycemic load (GL), 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 (IGFs),” said Stephanie Melkonian, postdoctoral fellow with Wu’s team and lead author of the study. “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 clarify the associations between GI, GL 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 GI and GL was determined using published food GI values, and subjects were divided into five equal groups, based on their GI and GL values.
Interestingly, GL 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 Wu.
Read more about this study in the MD Anderson Newsroom.