Based on the results of a population-based cohort study published in Annals of Family Medicine by Wang et al, high dietary glycemic index is linked to increased risks of lung cancer, non–small cell lung cancer (NSCLC), and small cell lung cancer (SCLC), whereas glycemic load is inversely associated with lung cancer and NSCLC.
“Our findings support the hypothesis that consuming low–glycemic index and high–glycemic load foods, such as vegetables and whole grains, could be a dietary factor that decreases the risk of lung cancer,” the investigators commented.
Study Details
The investigators focused on data from the U.S. National Cancer Institute’s Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a population-based prospective cohort study of approximately 155,000 adults between the ages of 55 and 74 years from 1993 to 2001. Participants were randomly assigned to intervention (screened for cancers in the first 3–4 years) and control (usual care) arms. They completed a baseline questionnaire on demographics, lifestyle, and medical history, along with a dietary history questionnaire. Cancer diagnoses and mortality were tracked until 2009 and 2018, respectively.
The present study included 101,732 PLCO participants (male: n = 50,187; female: n = 51,545; median age = 62.5 years) who completed both questionnaires at study entry if randomized after 1998, or during the subsequent follow-up if randomized before 1998. All incident lung cancer cases were confirmed pathologically. Associations between dietary glycemic index and load and lung cancer risk were estimated using Cox regression modeling to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).
Key Findings
A total of 1,706 incident lung cancer events were documented, including 1,473 (86.3%) cases of NSCLC and 233 (13.7%) of SCLC, during a median follow-up of 12.2 years (1,213,533 person-years).
After multivariate adjustment, glycemic index was found to be positively associated with lung cancer (4th [Q4] vs 1st [Q1] quartile: HR = 1.13, 95% CI = 1.05–1.31), NSCLC (HR = 1.11, 95% CI = 1.05–1.29), and SCLC (HR = 1.34, 95% CI = 1.02–2.27). In contrast, dietary glycemic load appeared to be associated with a decreased risk of lung cancer (Q4 vs Q1: HR = 0.72, 95% CI = 0.57–0.90) and NSCLC (HR = 0.68, 95% CI = 0.53–0.87), but not SCLC (HR = 0.90, 95% CI = 0.51–1.58).
These findings were consistent across subgroup analyses stratified by age, sex, family history of lung cancer, body mass index, and smoking status, according to the investigators.
The investigators concluded, “We found that a high dietary glycemic index was positively associated with the risks of lung cancer, NSCLC, and SCLC after fully adjusting for potential confounders including key lung cancer risk factors and overall dietary quality. In contrast, higher glycemic load was significantly linked to a lower risk of lung cancer and NSCLC, but not SCLC, after considering various potential confounders. The robustness of these findings was maintained in subgroup analyses.”
They emphasized, however, that replication in diverse populations and further mechanistic studies are needed.
Kanran Wang, MD, PhD, of Chongqing University Cancer Hospital, China, is the corresponding author of the Annals of Family Medicine article.
Disclosure: The study was funded by Chongqing Shapingba District Technological Innovation Project and Chongqing Natural Science Foundation. The study authors reported no conflicts of interest.
