Researchers have discovered associations between elements of the intestinal microbiome (including specific microbes, signaling pathways, and microbiota-related metabolites) and risk of colorectal ...cancer (CRC). However, it is unclear whether changes in the intestinal microbiome contribute to the development of sporadic CRC or result from it. Changes in the intestinal microbiome can mediate or modify the effects of environmental factors on risk of CRC. Factors that affect risk of CRC also affect the intestinal microbiome, including overweight and obesity; physical activity; and dietary intake of fiber, whole grains, and red and processed meat. These factors alter microbiome structure and function, along with the metabolic and immune pathways that mediate CRC development. We review epidemiologic and laboratory evidence for the influence of the microbiome, diet, and environmental factors on CRC incidence and outcomes. Based on these data, features of the intestinal microbiome might be used for CRC screening and modified for chemoprevention and treatment. Integrated prospective studies are urgently needed to investigate these strategies.
The substantial burden of colorectal cancer and increasing trend in young adults highlight the importance of lifestyle modification as a complement to screening for colorectal cancer prevention. ...Several dietary and lifestyle factors have been implicated in the development of colorectal cancer, possibly through the intricate metabolic and inflammatory mechanisms. Likewise, as a key metabolic and immune regulator, the gut microbiota has been recognized to play an important role in colorectal tumorigenesis. Increasing data support that environmental factors are crucial determinants for the gut microbial composition and function, whose alterations induce changes in the host gene expression, metabolic regulation, and local and systemic immune response, thereby influencing cancer development. Here, we review the epidemiologic and mechanistic evidence regarding the links between diet and lifestyle and the gut microbiota in the development of colorectal cancer. We focus on factors for which substantial data support their importance for colorectal cancer and their potential role in the gut microbiota, including overweight and obesity, physical activity, dietary patterns, fiber, red and processed meat, marine omega-3 fatty acid, alcohol, and smoking. We also briefly describe other colorectal cancer-preventive factors for which the links with the gut microbiota have been suggested but remain to be mechanistically characterized, including vitamin D status, dairy consumption, and metformin use. Given limitations in available evidence, we highlight the need for further investigations in the relationship between environmental factors, gut microbiota, and colorectal cancer, which may lead to development and clinical translation of potential microbiota-based strategies for cancer prevention.
Crohn's disease and ulcerative colitis, collectively known as IBD, are chronic inflammatory disorders of the gastrointestinal tract. Although the aetiopathogenesis of IBD is largely unknown, it is ...widely thought that diet has a crucial role in the development and progression of IBD. Indeed, epidemiological and genetic association studies have identified a number of promising dietary and genetic risk factors for IBD. These preliminary studies have led to major interest in investigating the complex interaction between diet, host genetics, the gut microbiota and immune function in the pathogenesis of IBD. In this Review, we discuss the recent epidemiological, gene-environment interaction, microbiome and animal studies that have explored the relationship between diet and the risk of IBD. In addition, we highlight the limitations of these prior studies, in part by explaining their contradictory findings, and review future directions.
Diet has an important role in the development of colorectal cancer. In the past few decades, findings from extensive epidemiologic and experimental investigations have linked consumption of several ...foods and nutrients to the risk of colorectal neoplasia. Calcium, fiber, milk, and whole grains have been associated with a lower risk of colorectal cancer, and red meat and processed meat have been associated with an increased risk. There is substantial evidence for the potential chemopreventive effects of vitamin D, folate, fruits, and vegetables. Nutrients and foods also may interact, as a dietary pattern, to influence colorectal cancer risk. Diet likely influences colorectal carcinogenesis through several interacting mechanisms. These include the direct effects on immune responsiveness and inflammation, and the indirect effects of overnutrition and obesity—risk factors for colorectal cancer. Emerging evidence also implicates the gut microbiota as an important effector in the relationship between diet and cancer. Dietary modification therefore has the promise of reducing colorectal cancer incidence.
Aspirin (acetylsalicylic acid) has become one of the most commonly used drugs, given its role as an analgesic, antipyretic and agent for cardiovascular prophylaxis. Several decades of research have ...provided considerable evidence demonstrating its potential for the prevention of cancer, particularly colorectal cancer. Broader clinical recommendations for aspirin-based chemoprevention strategies have recently been established; however, given the known hazards of long-term aspirin use, larger-scale adoption of an aspirin chemoprevention strategy is likely to require improved identification of individuals for whom the protective benefits outweigh the harms. Such a precision medicine approach may emerge through further clarification of aspirin's mechanism of action.
IMPORTANCE: It is important to document patterns of prescription drug use to inform both clinical practice and research. OBJECTIVE: To evaluate trends in prescription drug use among adults living in ...the United States. DESIGN, SETTING, AND PARTICIPANTS: Temporal trends in prescription drug use were evaluated using nationally representative data from the National Health and Nutrition Examination Survey (NHANES). Participants included 37 959 noninstitutionalized US adults, aged 20 years and older. Seven NHANES cycles were included (1999-2000 to 2011-2012), and the sample size per cycle ranged from 4861 to 6212. EXPOSURES: Calendar year, as represented by continuous NHANES cycle. MAIN OUTCOMES AND MEASURES: Within each NHANES cycle, use of prescription drugs in the prior 30 days was assessed overall and by drug class. Temporal trends across cycles were evaluated. Analyses were weighted to represent the US adult population. RESULTS: Results indicate an increase in overall use of prescription drugs among US adults between 1999-2000 and 2011-2012 with an estimated 51% of US adults reporting use of any prescription drugs in 1999-2000 and an estimated 59% reporting use of any prescription drugs in 2011-2012 (difference, 8% 95% CI, 3.8%-12%; P for trend <.001). The prevalence of polypharmacy (use of ≥5 prescription drugs) increased from an estimated 8.2% in 1999-2000 to 15% in 2011-2012 (difference, 6.6% 95% CI, 4.4%-8.2%; P for trend <.001). These trends remained statistically significant with age adjustment. Among the 18 drug classes used by more than 2.5% of the population at any point over the study period, the prevalence of use increased in 11 drug classes including antihyperlipidemic agents, antidepressants, prescription proton-pump inhibitors, and muscle relaxants. CONCLUSIONS AND RELEVANCE: In this nationally representative survey, significant increases in overall prescription drug use and polypharmacy were observed. These increases persisted after accounting for changes in the age distribution of the population. The prevalence of prescription drug use increased in the majority of, but not all, drug classes.
CONTEXT Aspirin reduces risk of colorectal neoplasia in randomized trials and inhibits tumor growth and metastases in animal models. However, the influence of aspirin on survival after diagnosis of ...colorectal cancer is unknown. OBJECTIVE To examine the association between aspirin use after colorectal cancer diagnosis on colorectal cancer−specific and overall survival. DESIGN, SETTING, AND PARTICIPANTS Prospective cohort study of 1279 men and women diagnosed with stage I, II, or III colorectal cancer. Participants were enrolled in 2 nationwide health professional cohorts in 1980 and 1986 prior to diagnosis and followed up through June 1, 2008. MAIN OUTCOME MEASURE Colorectal cancer−specific and overall mortality. RESULTS After a median follow-up of 11.8 years, there were 193 total deaths (35%) and 81 colorectal cancer−specific deaths (15%) among 549 participants who regularly used aspirin after colorectal cancer diagnosis, compared with 287 total deaths (39%) and 141 colorectal cancer−specific deaths (19%) among 730 participants who did not use aspirin. Compared with nonusers, participants who regularly used aspirin after diagnosis experienced a multivariate hazard ratio (HR) for colorectal cancer−specific mortality of 0.71 (95% confidence interval CI, 0.53-0.95) and for overall mortality of 0.79 (95% CI, 0.65-0.97). Among 719 participants who did not use aspirin before diagnosis, aspirin use initiated after diagnosis was associated with a multivariate HR for colorectal cancer−specific mortality of 0.53 (95% CI, 0.33-0.86). Among 459 participants with colorectal cancers that were accessible for immunohistochemical assessment, the effect of aspirin differed significantly according to cyclooxygenase 2 (COX-2) expression (P for interaction = .04). Regular aspirin use after diagnosis was associated with a lower risk of colorectal cancer−specific mortality among participants in whom primary tumors overexpressed COX-2 (multivariate HR, 0.39; 95% CI, 0.20-0.76), whereas aspirin use was not associated with lower risk among those with primary tumors with weak or absent expression (multivariate HR, 1.22; 95% CI, 0.36-4.18). CONCLUSION Regular aspirin use after the diagnosis of colorectal cancer is associated with lower risk of colorectal cancer−specific and overall mortality, especially among individuals with tumors that overexpress COX-2.
Serrated polyps (SPs) and conventional adenomas are precursor lesions for colorectal cancer (CRC), but they are believed to arise via distinct pathways. We characterized risk factor profiles for SPs ...and conventional adenomas in a post hoc analysis of data from 3 large prospective studies.
We collected data from the Nurses’ Health Study, the Nurses’ Health Study 2, and the Health Professionals Follow-up Study on subjects who developed SPs or conventional adenomas. Our analysis comprised 141,143 participants who had undergone lower gastrointestinal endoscopy, provided updated diet and lifestyle data every 2–4 years, and were followed until diagnosis of a first polyp. We assessed 13 risk factors for CRC in patients with SPs or conventional adenomas and examined the associations according to histopathology features.
We documented 7945 SPs, 9212 conventional adenomas, and 2382 synchronous SPs and conventional adenomas during 18–20 years of follow-up. Smoking, body mass index, alcohol intake, family history of CRC, and height were associated with higher risk of SPs and conventional adenomas, whereas higher intake of vitamin D and marine omega-3 fatty acid were associated with lower risk. The associations tended to be stronger for synchronous SPs and conventional adenomas. Smoking, body mass index, and alcohol intake were more strongly associated with SPs than conventional adenomas (P for heterogeneity <.05), whereas physical activity and intake of total folate and calcium were inversely associated with conventional adenomas but not SPs. For SPs and conventional adenomas, the associations tended to be stronger for polyps in the distal colon and rectum, of 10 mm or larger or with advanced histology.
In an analysis of data from 3 large prospective studies, we found that although SPs and conventional adenomas share many risk factors, some factors are more strongly associated with one type of lesion than the other. These findings provide support for the etiologic heterogeneity of colorectal neoplasia.
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High-quality evidence indicates that regular use of aspirin is effective in reducing the risk for precancerous colorectal neoplasia and colorectal cancer (CRC). This has led to US and international ...guidelines recommending aspirin for the primary prevention of CRC in specific populations. In this review, we summarize key questions that require addressing prior to broader adoption of aspirin-based chemoprevention, review recent evidence related to the benefits and harms of aspirin use among specific populations, and offer a rationale for precision prevention approaches. We specifically consider the mechanistic implications of evidence showing differences in aspirin's effects according to age, the potential role of modifiable mechanistic biomarkers for personalizing prevention, and emerging evidence that the gut microbiota may offer novel aspirin-associated preventive targets to reduce high-risk neoplasia.
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