Dietary carbohydrate intake is associated with a lower risk of breast cancer: a meta-analysis of cohort studies

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.

Macronutrient composition of plant-based diets and breast cancer risk: the E3N prospective cohort study

PURPOSE

Recent evidence suggests that plant-based diets may reduce the risk of breast cancer (BC). However, the macronutrient composition of plant-based diets and its potential impact on BC risk has not been well explored. This analysis investigated the association of macronutrient composition with BC risk across a spectrum of plant-based diet indexes using a multidimensional approach.

DESIGN

This study followed 64,655 participants from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) cohort from 1993 to 2014. Diets were evaluated using validated 208-item diet history questionnaires at baseline (1993) and follow-up (2005), to calculate adherence to the overall plant-based diet (PDI), healthful plant-based diet (hPDI), and unhealthful plant-based diet (uPDI). The association of macronutrient composition with BC risk was assessed via generalized additive time-dependent Cox models across different levels of these indexes. Response surfaces were generated to visualize compositional associations at the 25th, 50th, and 75th percentile of each index (low, moderate, and high).

RESULTS

A total of 3,932 incident BC cases were identified during the 21-year follow-up. There was a significant association between macronutrient composition and BC risk for hPDI, uPDI, and PDI (all P < 0.001). Akaike information criterion favored the hPDI model for characterizing the association between macronutrients and BC. BC risk was highest for individuals with a lower hPDI score who also consumed a diet containing lower protein (10%), lower carbohydrate (35%), and higher fat (55%). The lowest risk of BC was observed in those with higher hPDI scores with the lowest intake of protein (10%). At higher PDI and uPDI, diets containing higher protein (30%) and fat (45%) had the highest BC risk.

CONCLUSION

These results demonstrate a complex relationship between macronutrient composition, plant-based diet quality, and BC risk. Further research is needed to examine specific foods that may be driving these associations.

REGISTRY

The protocol is registered at clinicaltrials.gov as NCT03285230.

High and low dietary fiber consumption and cancer risk: a comprehensive umbrella review with meta-meta-analysis involving meta-analyses of observational epidemiological studies

It is a well-known fact that dietary fiber is recognized as one of the essential components of a healthy diet. The aim of this paper was to investigate the impact of dietary fiber on the incidence and mortality of various types of cancer, the current evidence in this field, and the biases of this evidence using the meta-meta-analysis method. We identified meta-analyses that particularly focused on the association between dietary fiber consumption and the risk/mortality of cancer. A structured and comprehensive computer literature search was undertaken in the electronic databases PubMed/Medline, Web of Science (WoS), and Scopus. The search yielded a total of 25 papers and 28 reports. In the pooled analysis, higher dietary fiber consumption was associated with a 22% lower cancer risk (OR = 0.78, 95% CI: 0.74-0.83, p < 0.001) and a 17% lower mortality (RR = 0.83, 95% CI: 0.78-0.90, p < 0.001). In the secondary meta-meta-analysis, it was observed that there was an inverse association between dietary fiber intake and digestive tract cancers (OR = 0.68, 95% CI: 0.62-0.76) and breast cancer (OR = 0.92, 95% CI: 0.90-0.94). Taken together, this paper suggests that promoting a high-fiber diet may be an effective strategy for the prevention and management of cancer.

Dietary carbohydrate quantity and quality and risk of cardiovascular disease, all-cause, cardiovascular and cancer mortality: A systematic review and meta-analysis

BACKGROUND & AIMS

Evidence remains conflicted on the association between dietary carbohydrate quantity and quality and risk of cardiovascular disease, all-cause, cardiovascular and cancer mortality, and such meta-analyses are lacking. The study aimed to conduct a systematic review and meta-analysis to synthesize the knowledge about their associations and to explore the dose-response relations.

METHODS

We comprehensively searched PubMed, EMBASE, and Web of Science up to March 2022 for observational studies investigating the associations in adults. Random effect model was used to estimate the summary relative risks (RRs) and 95% confidence intervals (CIs) and the dose-response association was explored by restricted cubic splines.

RESULTS

We obtained the data from 41 eligible studies. Compared with participants with lowest dietary carbohydrate intake, those with highest intake had an RR of 1.10 (95% CI 1.03-1.17, I2 = 52.8%) for cardiovascular disease, 1.10 (0.98-1.24, I2 = 65.5%) for coronary heart disease (CHD), 1.20 (1.08-1.34, I2 = 0) for stroke, 1.07 (1.00-1.14, I2 = 61.9%) for all-cause mortality, 1.02 (0.92-1.14, I2 = 51.3%) for cardiovascular mortality, and 1.01 (0.89-1.13, I2 = 56.7%) for cancer mortality. For each 5 %E increase in dietary carbohydrate intake, the summary RR was 1.02 (1.00-1.04, I2 = 66.8%) for cardiovascular disease, 1.04 (1.01-1.06, I2 = 0) for stroke but not significant for other outcomes. Restricted cubic splines showed linear associations with risk of cardiovascular disease (Pnon-linearity = 0.143), CHD (Pnon-linearity = 0.508), stroke (Pnon-linearity = 0.654) and non-linear associations with all-cause mortality (Pnon-linearity = 0.008) and cardiovascular mortality (Pnon-linearity = 0.055). Limited studies were found on the association of cardiovascular disease and mortality with dietary carbohydrate quality using a multidimensional and integrated indicator.

CONCLUSIONS

Increased consumption of dietary carbohydrate intake is associated with increased risk of cardiovascular disease, stroke, and all-cause mortality. Linear relation was found for cardiovascular disease and stroke but non-linear relation for all-cause mortality. More studies are warranted to investigate the association of dietary carbohydrate quality using a combined indicator and cardiovascular disease and mortality.

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 between household air pollution and all-cause and cause-specific mortality: a systematic review and meta-analysis

Recently, a growing number of epidemiological studies have examined the relationship between household air pollution (HAP) and all-cause and cause-specific mortality. While the results were not entirely consistent, the current study followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) protocol to conduct a comprehensive review and meta-analysis. Data sources were PubMed, Web of Science, Embase, and Cochrane Library for studies published up to 12 May 2022. The pooled relative risks (RRs) with 95% confidence intervals (CI) were used to estimate the effect of household air pollution on all-cause and cause-special mortality. Then I square value (I²) was used to assess heterogeneity, and random-effects model was used as the pooling method. Seventeen studies were included in the quantitative analysis. Our results showed a significant association between household air pollution and increased risks of all-cause mortality (RR = 1.12, 95% CI = 1.06-1.19) and cardiovascular disease mortality (RR = 1.13, 95% CI = 1.04-1.24). Similarly, the associations between household air pollution and mortality from other specific causes (respiratory, ischemic heart disease, stroke, and total cancer) were positive, although they were not statistically significant. The study suggests that exposure to household air pollution increases the risk of all-cause mortality and cardiovascular disease mortality. In addition, our results found a trend of increased mortality from the respiratory system, ischemic heart disease, stroke, and total cancer, with household air pollution.

The mortalities of female-specific cancers in China and other countries with distinct socioeconomic statuses: A longitudinal study

INTRODUCTION

Female-specific cancers seriously affect physical and psychological health of women worldwide.

OBJECTIVES

We aimed to elucidate trends in the age-standardized mortality rates (ASMRs) of breast cancer, cervical cancer, uterine cancer, and ovarian cancer in female populations with different socioeconomic statuses in China and in countries with different Human Development Index (HDI).

METHODS

A longitudinal study was performed using the data of cancer death in China and other 39 countries. The mortality rates were standardized with the Segi's world population. Trends in the mortalities were exhibited by estimated annual percentage change (EAPC). Pearson correlation was used to assess the association between EAPC and HDI.

RESULTS

In mainland China, female breast cancer, cervical cancer, uterine cancer, and ovarian cancer accounted for 6.60 %, 4.21 %, 2.50 %, and 2.02 % of cancer death (n = 1,314,040) in women with 1,220,251,032 person-years, respectively. The ASMRs of cervical cancer (EAPC = 3.87 %, P < 0.001) and ovarian cancer (EAPC = 1.81 %, P < 0.001) increased, that of female breast cancer unchanged, whereas that of uterine cancer was extremely higher and rapidly decreased (EAPC =  - 7.65 %, P < 0.001), during 2004-2019. The ASMRs of female breast and ovarian cancers were higher in urban and developed regions than in rural and undeveloped regions, in contrast to cervical and uterine cancers. The ASMRs of female breast and ovarian cancers were lower in China than in other countries, in contrast to uterine cancer. The ASMR of cervical cancer decreased, that of uterine cancer increased, in other countries during 2004-2017. EAPCs for the ASMRs of breast and ovarian cancers were inversely correlated to HDI.

CONCLUSION

The ASMRs of cervical and ovarian cancers increased, in contrast to uterine cancer, in China during socioeconomic transition. Trends in the ASMRs of breast and ovarian cancers were inversely associated with HDI. These data help control female-specific cancers.