Dietary glycemic index, glycemic load and cancer risk: a meta-analysis of prospective cohort studies

Bread Consumption and Cancer Risk: Systematic Review and Meta-Analysis of Prospective Cohort Studies

Because bread can contain potential carcinogens such as acrylamide, and is widely consumed, we conducted a systematic review and meta-analysis to determine whether bread consumption is associated with increased cancer risk. PubMed and Medline databases were searched up to 1 March 2024, for studies that provided hazard ratios (HRs) (or similar) for bread consumption and cancer incidence or mortality. Only prospective cohort studies were included. We used the Preferred Reporting Items of Systematic reviews and Meta-Analyses checklist. Meta-analysis was performed with Cochrane's RevMan 5.4.1 software using a DerSimonian-Laird random-effects model. Heterogeneity was assessed with Cochrane's Q (χ2) and I 2 statistics, and publication bias was assessed with Egger's test. Twenty-four publications met inclusion criteria, including 1,887,074 adults, and were included in the systematic review. Ten publications that provided HRs were included in the meta-analysis for highest compared with lowest intakes, and an additional 7 publications that provided mortality or incident rate ratios or relative risks were included in supplemental meta-analyses. Of 108 reported HRs (or similar), 97 (79%) were either not statistically significant (n = 86) or indicated lower cancer risk (n = 11) associated with the highest intakes of bread. The meta-analysis indicated that bread intake was not associated with site-specific cancer risk [HR: 1.01; 95% confidence interval (CI): 0.89, 1.14; P = 0.92; 8 publications] or total cancer mortality (HR: 0.90; 95% CI: 0.73, 1.11; P = 0.32; 2 publications). Supplemental meta-analyses using all risk estimates in addition to HRs confirmed these findings. Whole-grain bread was associated with a lower site-specific cancer risk, mainly because of reduced colorectal cancer risk. Results of the systematic review and meta-analysis indicate that bread consumption is not associated with increased site-specific cancer risk, whereas high whole-grain/nonwhite bread consumption is associated with lower total cancer mortality and colorectal cancer risk. This study was registered at Clinical Trials Registry of PROSPERO as registration number CRD42023414156.

Non-genetic factors and breast cancer: an umbrella review of meta-analyses

BACKGROUND

Previous research has found associations between various non-genetic factors and breast cancer (BrCa) risk. This study summarises and appraises the credibility of the available evidence on the association between non-genetic factors and BrCa risk.

METHODS

We conducted an umbrella review of meta-analyses. Medline, Scopus, and the Cochrane databases were systematically searched for meta-analyses examining non-genetic factors and BrCa incidence or mortality. The strength of the evidence was graded in four categories (i.e., weak, suggestive, highly suggestive, convincing).

RESULTS

A total of 781 meta-analyses from 280 publications were evaluated and graded. We included exposures related to anthropometric measurements, biomarkers, breast characteristics and diseases, diet and supplements, environment, exogenous hormones, lifestyle and social factors, medical history, medication, reproductive history, and pregnancy. The largest number of examined associations was found for the category of diet and supplements and for exposures such as aspirin use and active smoking. The statistically significant (P-value < 0.05) meta-analyses were 382 (49%), of which 204 (53.4%) reported factors associated with increased BrCa risk. Most of the statistically significant evidence (n = 224, 58.6%) was graded as weak. Convincing harmful associations with heightened BrCa risk were found for increased body mass index (BMI), BMI and weight gain in postmenopausal women, oral contraceptive use in premenopausal women, increased androstenedione, estradiol, estrone, and testosterone concentrations, high Breast Imaging Reporting and Data System (BIRADS) classification, and increased breast density. Convincing protective factors associated with lower BrCa risk included high fiber intake and high sex hormone binding globulin (SHBG) levels while highly suggestive protective factors included high 25 hydroxy vitamin D [25(OH)D] levels, adherence to healthy lifestyle, and moderate-vigorous physical activity.

CONCLUSIONS

Our findings suggest some highly modifiable factors that protect from BrCa. Interestingly, while diet was the most studied exposure category, the related associations failed to reach higher levels of evidence, indicating the methodological limitations in the field. To improve the validity of these associations, future research should utilise more robust study designs and better exposure assessment techniques. Overall, our study provides knowledge that supports the development of evidence-based BrCa prevention recommendations and guidance, both at an individual level and for public health initiatives.

TRIAL REGISTRATION

PROSPERO CRD42022370675.

Dietary insulin indices and low-carbohydrate diet and the odds of colorectal cancer: a case-control study

BACKGROUND

Regarding the role of insulin and insulin-inducing dietary factors in some cancers' etiology, we hypothesized that the risk of colorectal cancer may be lessened by following a lower carbohydrate and insulinogenic diet. Therefore, we performed this study to explore the association between a low-carbohydrate diet and insulin indices and the odds of colorectal cancer.

METHOD

This hospital-based case-control study was conducted on 150 newly diagnosed colorectal cancer patients and 300 healthy age- and sex-matched hospitalized controls. A valid and reliable food frequency questionnaire was used to calculate the insulin indices and low-carbohydrate diet score. Multivariate logistic regression was used to estimate the association between insulin indices and low-carbohydrate diet and the odds of colorectal cancer.

RESULT

After adjusting for potential confounders, individuals in the highest tertile of insulin indices had a higher risk of colorectal cancer (OR insulin index  = 3.46; 95% CI, 2.00-5.96; OR insulin load  = 2; 95% CI, 1.17-3.41). No association was found between a low-carbohydrate diet and colorectal cancer (OR = 1.55; 95% CI, 0.85-2.84).

CONCLUSION

Current results demonstrated that a high insulinemic diet was associated with a higher risk of colorectal cancer.

Diabetes Risk Reduction Diet and Colorectal Cancer Risk

BACKGROUND

Diabetes has been associated with colorectal cancer. We evaluated whether adherence to a diabetes risk reduction diet (DRRD) can favorably influence the risk of colorectal cancer.

METHODS

Data came from a multicentric Italian case-control study including 1,953 histologically confirmed colorectal cancer cases and 4,154 hospital controls admitted for acute nonneoplastic diseases. Diet was assessed through a validated and reproducible food frequency questionnaire. The DRRD score was computed assigning higher values for higher consumption of cereal fiber, fruit, coffee, nuts and a higher polyunsaturated/saturated fats ratio and for lower glycemic index and lower consumption of red/processed meat and sweetened beverages and fruit juices. The ORs and the corresponding 95% confidence intervals (CI) of colorectal cancer according to the DRRD score were obtained using logistic regression models adjusting for total energy intake and other major confounders.

RESULTS

The DRRD was inversely related to colorectal cancer risk. The ORs of colorectal cancer were 0.77 (95% CI, 0.67-0.89) for the third versus first score tertile (Ptrend < 0.001) and 0.92 (95% CI, 0.87-0.96) for a 3-point increment in the score. Inverse associations were observed for colon and rectal cancers and were consistent in strata of sex, age, and other major covariates.

CONCLUSIONS

A higher adherence to a DRRD was inversely associated with colorectal cancer risk.

IMPACT

Given the high incidence and mortality rates of colorectal cancer, adherence to a DRRD can have relevant prevention and public health implications.

Glycemic load, but not glycemic index, is associated with an increased risk of ovarian cancer: A systematic review and meta-analysis

The association between glycemic index (GI),glycemic load (GL) and ovarian cancer risk remains unclear. Carbohydrate intake promotes insulin secretion, leading to cell proliferation and invasion. We hypothesized that high GI and GL intake may increase ovarian cancer risk. Therefore, we conducted a meta-analysis after systematically searching PubMed, Embase, Web of Science, and Cochrane Library from inception to December 2022. Fixed- or random-effect models calculated the pooled relative risks (RRs) and corresponding 95% confidence intervals (CIs). Subgroup, sensitivity, publication bias analysis, and dose-response analysis were performed. Nine original studies were included, involving 4716 cases and 119,960 controls. No significant association was observed between GI or GL and ovarian cancer risk (GI: RR = 1.02 [95% CI, 0.83-1.26]; GL: RR = 1.11 [95% CI, 0.84-1.47]). Subgroup analysis suggested the results were not significantly modified by any group. Sensitivity analysis identified the sources of heterogeneity. No publication bias was observed. A linear positive dose-response relationship was observed between dietary GL and ovarian cancer risk after removing heterogeneous sources (RR = 1.11 [95% CI, 1.05-1.17], I2 = 32.9%, P = .23 at 50 U/d; RR = 1.04 [95% CI, 1.02-1.07], I2 = 19.1%, P = .29 at 20 U/d). These outcomes suggest that high dietary GL, but not GI, is associated with significantly increased ovarian cancer risk. Thus, sufficient intake of a low dietary GL is important for reducing ovarian cancer risk.

Low glycemic index noodle and pasta: Cereal type, ingredient, and processing

The consumption of noodles with a high glycemic index (GI) can affect health, prompting the need for dietary adjustments to manage abnormal blood glucose levels. This review delves into recent progress in low GI noodles and their potential effect for human well-being. Diverse approaches, encompassing the incorporation of soluble dietary fiber, modified starches, proteins, and plant polyphenols, have shown encouraging outcomes in diminishing the GI of noodles. Furthermore, variations in processing, storage, and cooking techniques can influence the GI of noodles, yielding both positive and negative impacts on their glycemic response. Soluble dietary fiber, protein cross-linkers, and plant polyphenols play a pivotal role in reducing the GI of noodles by hindering the interaction between digestive enzymes and starch, thereby curbing enzymatic activity. Future research spotlighting ingredients, processing methodologies, and the underlying mechanisms of low GI noodles will contribute substantively to the development of functional foods boosting enhanced nutritional profiles.

Common Misconceptions about Diet and Breast Cancer: An Unclear Issue to Dispel

Breast cancer (BC) constitutes a prevalent health condition among women. Recent years have witnessed the identification of dietary proto-oncogenic factors that deserve attention. Besides the well-known role of alcohol and red and processed meat in BC development, the impact of other dietary components remains unclear. Our narrative review aims to explore the diet-BC relationship, focusing on sugar, dairy, and soy consumption. We conducted a PubMed literature search covering the last decade (2013-2023) and included 35 papers. We found limited evidence on the association between high sugar intake and BC incidence. On the other hand, dairy and soy consumption displayed a protective effect in the majority of the analyzed papers. However, a significant degree of heterogeneity was reported among the results. Menopausal status and the specific BC molecular subtypes were the main factors influencing the interpretation of the results. Exploring dietary factors and BC revealed inconsistencies: high glycemic index post-menopause may be a risk factor, while sugar-sweetened drinks and artificial sweeteners yielded conflicting results; fermented dairy showed potential benefits, non-fermented dairy presented inconsistent findings; soy impact on BC varied according to molecular subtype, with some studies suggesting a positive association in luminal-like BC. Hence, further investigation is crucial to obtain a uniform consensus on the diet-BC relationship.

Association between glycemic traits and melanoma: a mendelian randomization analysis

Background: The causation of Glycemic Traits and risks of Melanoma remains unknown. We used Mendelian Randomization (MR) to assess the links between Glycemic Traits and Melanoma. Method: Pooled data from Genome-Wide Association Studies (GWAS) were utilized to examine the relationships that exist between Fasting Insulin (n = 26), 2-h Glucose (n = 10), Fasting Glucose (n = 47), HbA1c (n = 68), and Type-2 Diabetes (n = 105) and Melanoma. We evaluated the correlation of these variations with melanoma risk using Two-Samples MR. Result: In the IVW model, Fasting Glucose (OR = 0.99, 95%CI = 0.993-0.998, p < 0.05, IVW), Type-2 Diabetes (OR = 0.998, 95%CI = 0.998-0.999, p < 0.01, IVW) and HbA1c (OR = 0.19, 95%CI = 0.0415-0.8788, p < 0.05, IVW) was causally associated with a lower risk of Melanoma. In all models analyzed, there was no apparent causal relationship between Fasting Insulin and Melanoma risk. There was no obvious causal difference in the IVW analysis of 2-h Glucose and Melanoma, but its p < 0.05 in MR Egger (OR = 0.99, 95%CI = 0.9883-0.9984, p < 0.05, MR Egger), and the direction was consistent in other MR analyses, suggesting that there may be a causal relationship. Conclusion: The results of this study suggest that a higher risk of Fasting Glucose, Type-2 Diabetes, 2-h Glucose, and HbA1c may be associated with a lower risk of Melanoma. However, no causal relationship between fasting insulin and melanoma was found. These results suggest that pharmacological or lifestyle interventions that regulate plasma glucose levels in the body may be beneficial in the prevention of melanoma.

Determinants of motivation and adherence to a web application for health behaviour change: A qualitative study with cancer survivors

BACKGROUND

Given the increasing number of cancer survivors, eHealth may be an effective means to improve lifestyle-related behaviours. Limited data are available on the use of eHealth by post-cancer patients. The present study aimed to analyse the contexts of use to identify the determinants of cancer survivors' adherence and motivation to use a web application offering nutrition and physical activity coaching.

METHODS

Individual semi-structured interviews were conducted with cancer survivors who participated in an 8-week online program for health behaviour change. The interviews were analysed using thematic analysis.

RESULTS

Fifteen patients with a mean (SD) age of 62 (4.2) years completed the interview. Four themes relating to the environment and context of use were identified: digital use, social relations, health, and digital health interventions. Participants were familiar with digital tools through their professional work. Their motivation and adherence to the program improved through social relations; notably, a supportive family in addition to a trusted prescriber, continuity in the care pathway, and an appropriate choice of design features in the digital health intervention. With cancer survivorship, individuals no longer define themselves as sick but still need support to envisage the future more serenely.

CONCLUSIONS

Cancer survivorship plays a special role in people's adherence to online interventions for health behaviour change in addition to the influence of their social relations and health environment.

Global trends in incidence, death, burden and risk factors of early-onset cancer from 1990 to 2019

Objective

This study aimed to explore the global burden of early-onset cancer based on the Global Burden of Disease (GBD) 2019 study for 29 cancers worldwid.

Methods and analysis

Incidence, deaths, disability-adjusted life years (DALYs) and risk factors for 29 early-onset cancer groups were obtained from GBD.

Results

Global incidence of early-onset cancer increased by 79.1% and the number of early-onset cancer deaths increased by 27.7% between 1990 and 2019. Early-onset breast, tracheal, bronchus and lung, stomach and colorectal cancers showed the highest mortality and DALYs in 2019. Globally, the incidence rates of early-onset nasopharyngeal and prostate cancer showed the fastest increasing trend, whereas early-onset liver cancer showed the sharpest decrease. Early-onset colorectal cancers had high DALYs within the top five ranking for both men and women. High-middle and middle Sociodemographic Index (SDI) regions had the highest burden of early-onset cancer. The morbidity of early-onset cancer increased with the SDI, and the mortality rate decreased considerably when SDI increased from 0.7 to 1. The projections indicated that the global number of incidence and deaths of early-onset cancer would increase by 31% and 21% in 2030, respectively. Dietary risk factors (diet high in red meat, low in fruits, high in sodium and low in milk, etc), alcohol consumption and tobacco use are the main risk factors underlying early-onset cancers.

Conclusion

Early-onset cancer morbidity continues to increase worldwide with notable variances in mortality and DALYs between areas, countries, sex and cancer types. Encouraging a healthy lifestyle could reduce early-onset cancer disease burden.

Dietary glycemic index, glycemic load, and renal cancer risk: findings from prostate, lung, colorectal, and ovarian cancer trial

Background

Dietary glycemic index (GI) or glycemic load (GL) has been associated with the development of many cancers, but the evidence for renal cancer is still limited. The aim of the present study was to investigate the association between GI or GL and renal cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) Screening Trial.

Methods

The cohort for our analysis consisted of 101,190 participants. GI and GL were calculated from the FFQ data using previously published reference values. Multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression model after adjusting for most known renal cancer risk factors.

Results

During a median of 12.2 years of follow-up, 443 incident renal cancer cases occurred. Higher dietary GI was significantly associated with a higher risk of renal cancer (HR_Q3vsQ1: 1.38; 95% CI: 1.09-1.74; p for trend = 0.008). There was no significant association between dietary GL and renal cancer risk (HR_Q3vsQ1 = 1.12, 95% CI = 0.79-1.59, p for trend = 0.591). Spline regression plot revealed a higher risk of renal cancer with a higher GI but not GL. There was no statistical evidence for nonlinearity (p for nonlinearity >0.05).

Conclusion

In summary, findings of this large-scale prospective cohort study suggested that dietary GI may be associated with the risk of renal cancer. If confirmed in other populations and settings, dietary GI could be considered as a modifiable risk factor for renal cancer prevention.

Systematic Review and Meta-Analysis of the Impact of Bariatric Surgery on Future Cancer Risk

The study aimed to perform a systematic review and meta-analysis of the evidence for the prevention of future cancers following bariatric surgery. A systematic literature search of the Cochrane Library, Embase, Scopus, Web of Science and PubMed databases (2007–2023), Google Scholar and grey literature was conducted. A meta-analysis was performed using the inverse variance method and random effects model. Thirty-two studies involving patients with obesity who received bariatric surgery and control patients who were managed with conventional treatment were included. The meta-analysis suggested bariatric surgery was associated with a reduced overall incidence of cancer (RR 0.62, 95% CI 0.46–0.84, p < 0.002), obesity-related cancer (RR 0.59, 95% CI 0.39–0.90, p = 0.01) and cancer-associated mortality (RR 0.51, 95% CI 0.42–0.62, p < 0.00001). In specific cancers, bariatric surgery was associated with reduction in the future incidence of hepatocellular carcinoma (RR 0.35, 95% CI 0.22–0.55, p < 0.00001), colorectal cancer (RR 0.63, CI 0.50–0.81, p = 0.0002), pancreatic cancer (RR 0.52, 95% CI 0.29–0.93, p = 0.03) and gallbladder cancer (RR 0.41, 95% CI 0.18–0.96, p = 0.04), as well as female specific cancers, including breast cancer (RR 0.56, 95% CI 0.44–0.71, p < 0.00001), endometrial cancer (RR 0.38, 95% CI 0.26–0.55, p < 0.00001) and ovarian cancer (RR 0.45, 95% CI 0.31–0.64, p < 0.0001). There was no significant reduction in the incidence of oesophageal, gastric, thyroid, kidney, prostate cancer or multiple myeloma after bariatric surgery as compared to patients with morbid obesity who did not have bariatric surgery. Obesity-associated carcinogenesis is closely related to metabolic syndrome; visceral adipose dysfunction; aromatase activity and detrimental cytokine, adipokine and exosomal miRNA release. Bariatric surgery results in long-term weight loss in morbidly obese patients and improves metabolic syndrome. Bariatric surgery may decrease future overall cancer incidence and mortality, including the incidence of seven obesity-related cancers.

Associations between overall, healthful, and unhealthful low-fat dietary patterns and breast cancer risk in a Mediterranean cohort: The SUN project

OBJECTIVES

Dietary patterns may have a greater influence on human health than individual foods or nutrients, and they are also of substantial interest in the field of breast cancer prevention. Beyond the adequate balance of macronutrients, evidence indicates that the quality of macronutrient sources may play an important role in health outcomes. We sought to examine the relationship between healthful and unhealthful low-fat dietary patterns in relation to breast cancer.

METHODS

We used observational data from a Mediterranean cohort study (the Seguimiento Universidad de Navarra project). We prospectively followed 10 930 middle-aged women initially free of breast cancer during a median follow-up of 12.1 y. We calculated an overall, an unhealthful, and a healthful low-fat diet score, based on a previously validated 136-item food frequency questionnaire and grouped participants into tertiles. Incident breast cancer-overall and stratified by menopausal status-was the primary outcome. It was self-reported by participants and confirmed based on medical reports or consultation of the National Death Index. We used multivariable Cox regression models adjusted for potential confounders.

RESULTS

During 123 297 person-years of follow-up, 150 cases of incident breast cancer were confirmed. No significant associations were observed for overall or premenopausal breast cancer. For postmenopausal women, we observed a significant association for moderate adherence to the unhealthful low-fat dietary score and postmenopausal breast cancer (comparing tertile 2 to tertile 1; hazard ratio = 2.18; 95% confidence interval, 1.15-4.13).

CONCLUSIONS

In conclusion, no clear associations were observed, although more research is needed to address the association between an unhealthful dietary pattern and postmenopausal breast cancer risk.

Association of nutritional glycaemic indices with global DNA methylation patterns: results from the Moli-sani cohort

BACKGROUND

High dietary glycaemic index (GI) and load (GL) have been associated with increased risk of various cardiometabolic conditions. Among the molecular potential mechanisms underlying this relationship, DNA methylation has been studied, but a direct link between high GI and/or GL of diet and global DNA methylation levels has not been proved yet. We analyzed the associations between GI and GL and global DNA methylation patterns within an Italian population.

RESULTS

Genomic DNA methylation (5mC) and hydroxymethylation (5hmC) levels were measured in 1080 buffy coat samples from participants of the Moli-sani study (mean(SD) = 54.9(11.5) years; 52% women) via ELISA. A 188-item Food Frequency Questionnaire was used to assess food intake and dietary GI and GL for each participant were calculated. Multiple linear regressions were used to investigate the associations between dietary GI and GL and global 5mC and 5hmC levels, as well as the proportion of effect explained by metabolic and inflammatory markers. We found negative associations of GI with both 5mC (β (SE) = - 0.073 (0.027), p = 0.007) and 5hmC (- 0.084 (0.030), p = 0.006), and of GL with 5mC (- 0.14 (0.060), p = 0.014). Circulating biomarkers did not explain the above-mentioned associations. Gender interaction analyses revealed a significant association of the gender-x-GL interaction with 5mC levels, with men showing an inverse association three times as negative as in women (interaction β (SE) = - 0.16 (0.06), p = 0.005).

CONCLUSIONS

Our findings suggest that global DNA methylation and hydroxymethylation patterns represent a biomarker of carbohydrate intake. Based on the differential association of GL with 5mC between men and women, further gender-based separate approaches are warranted.

Artificially Sweetened Beverage Consumption and Cancer Risk: A Comprehensive Dose-Response Meta-Analysis of Prospective Studies

The impact of artificially sweetened beverages (ASBs), alternatives to sugar-sweetened beverages, on cancer incidence remains controversial. We conducted a meta-analysis of prospective studies to assess the association of daily ASB intake with cancer risk. A systematic search was performed between January 1967 and September 2022. Risk ratios (RR) or hazard ratios (HR) were extracted and pooled. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach was used for the assessment of the certainty of evidence. The study was registered at PROSPERO (CRD42022312171). Overall, 14 articles with 17 cohorts were included. There was no significant association between daily ASB consumption and risk of overall cancer (highest versus lowest category: n = 17, RR = 1.03, 95% CI: 0.96-1.11, p = 0.407). For site-specific cancer analysis, the risk of non-lymphoid leukemia was elevated with high ASB intake (n = 3, RR = 1.35, 95% CI: 1.03-1.77, p = 0.030), while risk of colorectal cancer was decreased (n = 3, RR = 0.78, 95% CI: 0.62-0.99, p = 0.037). Dose-response analysis indicated a positive linear association between ASB intake and the risk of leukemia (p_-linear = 0.027). The risk increased by 15% per one serving (355 mL) daily ASB intake increment (RR = 1.15, 95% CI: 1.02-1.30). In conclusion, ASB consumption might be positively associated with the risk of leukemia and negatively associated with the risk of colorectal cancer.

Receptor of advanced glycation end-products axis and gallbladder cancer: A forgotten connection that we should reconsider

Compelling evidence derived from clinical and experimental research has demonstrated the crucial contribution of chronic inflammation in the development of neoplasms, including gallbladder cancer. In this regard, data derived from clinical and experimental studies have demonstrated that the receptor of advanced glycation end-products (RAGE)/AGEs axis plays an important role in the onset of a crucial and long-lasting inflammatory milieu, thus supporting tumor growth and development. AGEs are formed in biological systems or foods, and food-derived AGEs, also known as dietary AGEs are known to contribute to the systemic pool of AGEs. Once they bind to RAGE, the activation of multiple and crucial signaling pathways are triggered, thus favoring the secretion of several proinflammatory cytokines also involved in the promotion of gallbladder cancer invasion and migration. In the present review, we aimed to highlight the relevance of the association between high dietary AGEs intakes and high risk for gallbladder cancer, and emerging data supporting that dietary intervention to reduce gallbladder cancer risk is a very attractive approach that deserves much more research efforts.

Glycemic index, glycemic load, and lung cancer risk: A meta-analysis of cohort and case-control studies

Objective

Glycemic index (GI) or glycemic load (GL) has been investigated in the field of cancer research for several years. However, the relationship between GI or GL and lung cancer risk remains inconsistent. Therefore, this study aimed to summarize previous findings on this relationship.

Methods

PubMed, Embase, Scopus, Web of Science databases, and Cochrane Library were searched by July 2021. This review was conducted in accordance with the PRISMA guidelines. A fixed or random-effects model was adopted for meta-analysis to compute the pooled relative risks (RR) and their corresponding 95% confidence intervals (CIs). Subgroup analyses, sensitivity analyses, and publication bias analyses were also performed.

Results

In total, nine articles were included, with four case-control studies and five cohort studies, including 17,019 cases and 786,479 controls. After merging the studies, pooled multivariable RRs of lung cancer based on the highest versus the lowest intake were 1.14 (95%CI: 1.03–1.26) and 0.93 (95%CI: 0.84–1.02) for GI and GL. Results persisted in most stratifications after stratifying by potential confounders in the relationship between GI and lung cancer risk. There was a non-linear dose response relation for GI with lung caner risk.

Conclusion

GI typically has a positive relationship with lung cancer risk. However, no associations between GL and lung cancer risk were observed based on current evidence, suggesting that this issue should be studied and verified further to substantiate these findings.