Omega-3 PUFA intake and the risk of digestive system cancers: A meta-analysis of observational studies.

BACKGROUND: A growing number of epidemiological studies have suggested a possible association between long-chain omega-3 polyunsaturated fatty acid (PUFA) intake and the risk of cancers, but the results have been inconsistent. We aimed to conduct a meta-analysis to assess the association of omega-3 PUFA consumption with digestive system cancers. METHODS: Relevant observational studies were identified through a comprehensive search of PubMed, Embase, and the Web of Science through December 2019 and by reviewing the references of the retrieved articles. The relative risks (RRs) of digestive system cancers associated with omega-3 PUFA intake were estimated using a random-effect model and were stratified by region, sex, study design, type of omega-3 PUFAs, smoking status, alcohol consumption, BMI, and physical activity. RESULTS: Twenty-five studies (8 case-control studies and 17 cohort studies) involving 1,247,271 participants and 23,173 patients with digestive system cancers were included in this analysis. The risk of digestive system cancers decreased by 17% in individuals who consumed omega-3 PUFAs (RR = 0.83, 95% confidence interval (CI), 0.76-0.91). The risk estimates of digestive system cancers varied by cancer sites, study location, study design, type of omega-3 PUFAs, and other confounders (smoking, alcohol consumption, body mass index, and physical activity). Visual inspection of funnel plots and the Begg's and Egger's tests revealed no evidence of publication bias. CONCLUSION: The findings show that omega-3 PUFAs should be as a healthy dietary component for the prevention of digestive system cancers. Cancer incidence decreases with increasing omega-3 PUFAs intake for most digestive system cancer sites. The relation between omega-3 PUFAs and digestive system cancers RR is similar among different populations.

[Influence of food or food groups intake on the occurrence and/or protection of different types of cancer: systematic review]. / Influencia de la ingesta de alimentos o grupos de alimentos en la aparición y/o protección de los diversos tipos de cáncer: revisión sistemática.

INTRODUCTION: Introduction: the diet plays an important role in the origin and prevention of multiple chronic degenerative diseases, such as cardiovascular diseases or cancer. Objective: the main objective of this paper is to analyze the studies that are focused on researching the relationship between the consumption of the particular groups of foods and its importance on the increase and for prevention of the risk of cancer appearance. Methods: a bibliographical review was carried out in the main international databases (PubMed, Scopus and Nutrition Reference). The results were structured in two main sections: those related with the increase of cancer risk and food related with the increase of cancer risk. In the present review, 104 scientific articles have been evaluated. Results: the results have shown a positive association between red meat and colon cancer, alcoholic drinks and liver cancer, and salt and gastric cancer. The Mediterranean diet was associated in a preventive way with digestive and respiratory tract cancer. Conversely, no statistically significant association was found between dairy products and ovarian cancer, carbohydrates and sugars and pancreatic cancer, and tae and breast cancer. Conclusions: as a result, healthy eating guidelines, such as the Mediterranean diet, based on lower consumption of red meat, alcoholic drinks and salt, might contribute to reducing the incidence of colon cancer, liver cancer and gastric cancer.

INTRODUCCIÓN: Introducción: la dieta tiene un importante papel en la formación y en la prevención de múltiples enfermedades crónicas-degenerativas, como son las enfermedades cardiovasculares o el cáncer. Objetivos: el objetivo principal consiste en analizar los estudios que centren su investigación en conocer la relación entre el consumo de determinados grupos de alimentos y su función en el aumento y/o prevención del riesgo de aparición de diversos tipos de cáncer. Métodos: se realizó una revisión sistemática en bases de datos internacionales (PubMed, Scopus y Nutrition Reference). Los estudios fueron estructurados en dos bloques principales: relacionados con el aumento del riesgo de cáncer y alimentos relacionados con el aumento del riesgo de cáncer. Los estudios evaluados en la presente revisión han sido un total de 104 artículos científicos. Resultados: los resultados han mostrado una asociación positiva entre la carne roja y el cáncer de colon, las bebidas alcohólicas y el cáncer de hígado y la sal y el cáncer gástrico. La dieta mediterránea se asoció de manera preventiva con el cáncer del tracto digestivo y respiratorio, mientras que, por otro lado, no se ha encontrado asociación estadísticamente significativa entre el consumo de lácteos y el cáncer de ovario, los carbohidratos o azúcares y el cáncer de páncreas y el té y el cáncer de mama. Conclusiones: por todo ello, patrones de alimentación saludable como la dieta mediterránea, basados en una menor ingesta de carne roja, bebidas alcohólicas y sal, contribuyen a una reducción en la incidencia del cáncer de colon, cáncer de hígado y cáncer de estómago.

N-3 fatty acids, cancer and cachexia: a systematic review of the literature.

Use of n-3 fatty acids (FA) has been reported to be beneficial for cancer patients. We performed a systematic review of the literature in order to issue recommendations on the clinical use of n-3 FA in the cancer setting. A systematic search was performed in MEDLINE, EMBASE, Cochrane and Healthstar databases. We selected clinical trials or prospective observational studies including patients with cancer and life expectancy >2 months, in which enteral supplements with n-3 FA were administered. Parameters evaluated individually were clinical (nutritional status, tolerance, survival and hospital stays), biochemical (inflammatory mediators), and functional (functional status, appetite and quality of life (QoL)). Seventeen studies met the inclusion criteria; eight were of high quality. The panel of experts established the following evidence: (1) oral supplements with n-3 FA benefit patients with advanced cancer and weight loss, and are indicated in tumours of the upper digestive tract and pancreas; (2) the advantages observed were: increased weight and appetite, improved QoL, and reduced post-surgical morbidity; (3) there is no defined pattern for combining different n-3 FA, and it is recommended to administer > 1.5 g/day; and (4) better tolerance is obtained administering low-fat formulas for a period of at least 8 weeks. All the evidences were grade B but for 'length of treatment' and 'advantage of survival' it was grade C. Our findings suggest that administration of n-3 FA (EPA and DHA) in doses of at least 1.5 g/day for a prolonged period of time to patients with advanced cancer is associated with an improvement in clinical, biological and QoL parameters.

[A case-control study on drinking green tea and decreasing risk of cancers in the alimentary canal among cigarette smokers and alcohol drinkers].

OBJECTIVE: To explore the role of green tea in decreasing the risks of gastric cancer, liver cancer, esophageal cancer among alcohol drinkers or cigarette smokers. METHODS: A population based case-control study was conducted in Taixing, Jiangsu province. RESULTS: In Taixing city, identified cases of stomach, liver and esophageal cancers were chosen with informed consent. The numbers were 206, 204, 218 respectively. Controls were chosen from normal population having lived in the area for longer than 10 years, also with informed consent. Green tea drinking seemed to have decreased 81%, 78%, 39% risk for the development of gastric cancer, liver cancer and esophageal cancer among alcohol drinkers. It might also have decreased 16%, 43%, 31% on the risks of developing the three kinds of cancers among cigarette smokers. Interaction assessment showed that drinking green tea could significantly decrease the risk of gastric cancer and liver cancer among alcohol drinkers, with ORs of interaction item 0.23 (95% CI: 0.10 - 0.55) and 0.25 (95% CI: 0.11 - 0.57) respectively. CONCLUSION: Habit of drinking green tea seemed to have significant protective effects on the development of both gastric and liver cancer among alcohol drinkers while, green tea also having some protective effect on esophageal cancer among alcohol drinkers and on three kinds of cancers among cigarette smokers.

A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagasaki (Japan).

OBJECTIVES: Laboratory and animal studies have shown a protective effect of green tea on cancer of different sites, but epidemiological evidence is limited and inconclusive. This prospective study in Japan examined the association between green tea consumption and cancer incidence. METHODS: Subjects were 38,540 people (14,873 men, mean age 52.8 years; 23,667 women, mean age 56.8 years) who responded to a mail survey carried out between 1979 and 1981. A self-administered questionnaire ascertained consumption frequency of green tea using precoded answers (never, once per day, twice to four times per day, and five or more times per day). Follow-up continued until 31 December 1994. The study analyzed solid cancers (n = 3881); hematopoietic cancers (188); cancers of all sites combined (4069); and cancer of specific sites with more than 100 cases, i.e. stomach (901), colon (432), rectum (193), liver (418), gallbladder (122), pancreas (122), lung (436), breast (281), and bladder (122). Poisson regression was used to allow for city, gender, age, radiation exposure, smoking status, alcohol drinking, body-mass index, education level, and calendar time. RESULTS: Green tea consumption was virtually unrelated to incidence of cancers under study. The relative risks of all cancers for those consuming green tea twice to four times per day and five or more times per day were 1.0 (95% confidence interval 0.91-1.1) and 0.98 (0.88-1.1), respectively, as compared with those consuming green tea once per day or less. CONCLUSION: Our findings do not provide evidence that regular green tea consumption is related to reduced cancer risks.

Tea and coffee consumption and the risk of digestive tract cancers: data from a comparative case-referent study in Japan.

OBJECTIVES: The purpose of this study was to examine the hypothesis that tea and coffee consumption have a protective effect against development of digestive tract cancers. METHODS: A comparative case-referent study was conducted using Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC) data from 1990 to 1995 in Nagoya, Japan. This study comprised 1,706 histologically diagnosed cases of digestive tract cancers (185 esophagus, 893 stomach, 362 colon, 266 rectum) and a total of 21,128 non-cancer outpatients aged 40 years and over. Logistic regression was used to analyze the data, adjusting for gender; age; year and season at hospital-visit; habitual smoking and alcohol drinking; regular physical exercise; fruit, rice, and beef intake; and beverage intake. RESULTS: The odds ratio (OR) of stomach cancer decreased to 0.69 (95 percent confidence interval [CI] = 0.48-1.00) with high intake of green tea (seven cups or more per day). A decreased risk was also observed for rectal cancer with three cups or more daily intake of coffee (OR = 0.46, CI = 0.26-0.81). CONCLUSIONS: The results suggest the potential for protective effect against site-specific digestive tract cancer by consumption of green tea and coffee, although most associations are limited only to the upper category of intake and have no clear explanation for site-specificity.

Influence of tea catechins on the digestive tract.

Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage are excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved in tube-fed patients by administering 100 mg of tea catechins (equivalent to a cup of green tea) three times daily with meals for 3 weeks. When catechin administration ceased, the effects reversed after 1 week. Catechins should be considered further in colon carcinogenesis studies.

Development of chemopreventive agents for lung and upper aerodigestive tract cancers.

The lung and upper aerodigestive tract (oral cavity, larynx, pharynx, upper esophagus) will harbor the greatest proportion (approximately 20%) of estimated new cancer cases in 1992. The estimated mortality rate is even higher (32%), which is reflected in a 5-year survival rate of only 7% and 12% for esophageal and lung cancer, respectively. Tobacco use appears to remain the major cause of aerodigestive cancers despite efforts at primary prevention--cessation of exposure. Another strategy to decrease this public health problem is secondary prevention or chemoprevention. Cancer chemoprevention is defined as intervention with chemical agents before invasion to halt or slow the carcinogenic process; potential agents may include minor dietary constituents and pharmaceuticals. The main objective of the Division of Cancer Prevention and Control (DCPC), National Cancer Institute, is to develop promising chemopreventive drugs for use in humans. The testing of cancer chemopreventives for efficacy in the clinic differs from that of cancer treatment drugs. Chemopreventive drug trials involve healthy target populations, and the endpoints are reduced cancer incidence or mortality, or increased latency, with no to minimal toxicity. The lung and upper aerodigestive tract represent a unique opportunity for intervention in this setting. Even with cessation of tobacco exposure, the risk of cancer in the entire epithelium remains high for years due to the "field cancerization" effect. Some of the first chemopreventive trials made use of this system due to the availability of a study population with a tissue at demonstrably high risk for malignant progression. Much of the evidence for chemopreventive efficacy is in the oral cavity because of the well-defined epithelial neoplastic progression, the existence of well-established preclinical models, and relative ease of tissue monitoring and sampling. In one of the first randomized trials, Hong and co-workers demonstrated that 13-cis-retinoic acid prevents the appearance of second primary tumors in patients previously treated for squamous cell carcinomas of the oral cavity and upper respiratory tract. Even using a high risk population, chemoprevention trials involve large sample sizes, lengthy duration and follow-up, and high cost. To circumvent these problems, the use of intermediate biomarkers as surrogate endpoints is being explored. Intermediate biomarkers are defined as biological alterations in tissue (histological, genetic, biochemical, proliferative, differentiation-related) occurring prior to cancer development. In the oral cavity, studies using modulation of a histological intermediate biomarker, dysplastic leukoplakia, as the endpoint have demonstrated response to a retinoid.(ABSTRACT TRUNCATED AT 400 WORDS)