摘要:

The consensus meeting on 'Cereals, fibre and colorectal and breast cancers' was attended by 17 dietary and cancer experts; a further eight who could not attend the discussions were deemed corresponding participants and gave their views by post and telephone. The agreed consensus statement is given here.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Burkitt and Walker first promoted the idea that colorectal cancer could be prevented by dietary fibre. Early studies of this hypothesis were hampered by problems with the definition of dietary fibre, and the lack of good analytical methods to assess its intake. Dietary fibre is a complex carbohydrate of plant origin that escapes small-bowel digestion and so reaches the colon. It was assumed that the major plant polysaccharide, starch, is completely digested in the small bowel, and that dietary Fibre consists of nonstarch polysaccharide. However, there is some evidence that nonstarch polysaccharide accounts for only about 25% of the true intake of dietary fibre. Therefore it is better at present to use fibre-rich foods as a measure rather than the inaccurate assays of dietary fibre found in epidemiological studies. A re-examination of the epidemiological literature has shown that although the strength of the protection given by dietary fibre may be disputed, there is no doubt about the protection afforded by Cereal fibre.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

A recent analysis of Food and Agriculture Organization (FAO) data and mortality data has shown that not all fibre sources are equally protective against colorectal and breast cancers. We correlated the risk of cancers of the colon and breast with the intake of cereals, starchy roots, vegetables, fruits and total energy, either concurrently with the cancer mortality data, or from 20 years earlier. The patterns of the effects of cereals, starchy roots, vegetables and fruits were very different, with cereals and vegetables being protective against both cancers, fruit having no effect and starchy roots having a very weak and non-significant promoting effect. There is strong current interest in the protective effects of fruit and vegetables against cancers at a number of sites. Our analysis showed that only the current intake of vegetables was protective. Intake early in life seemed to offer no protection. The protective effect of cereals was manifest both early in life as well as for current intake for female breast and colorectal cancer, but only for the current period for male colorectal cancer. Calorie restriction, but only early in life, provides protection against all three cancers. Most advice on healthy eating, other than that for small children, is given to (and taken by) the senior age groups and these are the ones likely to benefit. In our study fruit intake was not correlated at all with the risk of either colorectal or breast cancers at either time period. Fruit is clearly more protective against cancers of the upper digestive tract and respiratory tract than against the cancers considered here.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

To elucidate the influence of diet on colorectal carcinogenesis, 1225 subjects with cancer of the colon, 728 with cancer of the rectum and 4154 controls, hospitalized with acute non-neoplastic diseases, were interviewed between 1992 and 1996 in six Italian areas. The validated food frequency questionnaire included 79 questions on food items and recipes which were grouped into 16 food groups. After allowing for nondietary confounding factors and total energy intake, a significant trend towards an increasing risk of colorectal cancer with increasing intake was found for bread and cereal dishes (odds ratio for increase of one daily serving 1.11), cakes and desserts (odds ratio 1.02) and refined sugar (odds ratio 1.11). The intake of fish (odds ratio 0.53), raw and cooked vegetables (odds ratios 0.79 and 0.65, respectively) and fruit (odds ratio 0.93) showed an inverse association with risk. Wholemeal bread was consumed by only 12.5% of cases and 13.9% of controls and, at variance with refined bread, did not show a significant direct association with colorectal cancer risk (odds ratio 0.88). In view of these findings, current hypotheses on the carcinogenic effects of refined starchy foods and refined sugar should be revised to take into account the digestive physiology of carbohydrates and the possible relationship between insulin and colon cancer. The beneficial influence of most vegetables is confirmed, and a possible difference between refined and wholemeal bread is suggested.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The possible relationship between fibre intake and breast cancer risk has been considered in several studies, but the issue is still unsettled. Epidemiological data are compatible with moderate protection from fibre-rich foods against the risk of breast cancer, but also with an absence of association. The apparently inconsistent results may be due to chance or bias, to different approaches to data analysis and interpretation, but may also reflect heterogeneity in the dietary sources of fibres (cereals or vegetables and fruit) in various populations, and different correlates of fibre intake.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Epidemiological studies have emphasized the importance of diet in the etiology of large bowel cancer. A high intake of dietary fibre has been hypothesized to decrease the risk of colorectal cancer. This hypothesis is now being tested within the framework of intervention studies. Supplemental fibre is being used in four chemopreventive trials as wheat bran (22.5 g/day together with vitamins C and E, New York study; 25 g/day, Australian study; 50 g/day, Toronto study; 13.5 g/day, Arizona study) and in one trial as ispaghula husk (a mucilaginous substance) at 3.8 g/day (European Cancer Prevention Organization study). One study is evaluating the effect of fibre on adenoma size in patients with familial polyposis and an intact rectum, and the other four studies are focusing on the recurrence of adenoma in patients with previous adenomas. The results available so far provide some evidence for the inhibition of adenoma growth through a high-fibre and/or low-fat diet. Further results are expected within a year. If there is sufficient evidence for a protective effect of dietary fibre on colorectal carcino-genesis, a simple, safe and inexpensive prophylaxis for a very common cancer will be indicated.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The relationship between fibre intake and risk of colorectal cancer has occupied the attention of scientists and physicians for more than two decades. No satisfying, generalized mechanism for the observed effects has yet been formulated, which is not surprising, since fibre is only one component of a varied diet. Currently, the effects of the short-chain fatty acids offer the most interesting and plausible leads.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Reproducible high-performance liquid chromatography methods have been developed and validated which allow an accurate quantification of phytic acid in faeces and food and reactive oxygen species in anin vitromodel system and in faecal specimens. When applied to the evaluation of reactive oxygen species generation by faeces, this method has shown that 1:100 dilutions of matrix obtained from stool samples of adenoma patients are capable of generating significant quantities of reactive oxygen species as evinced by the production of diphenols from salicylic acid. Moreover, it has been shown that the major product of HO attack on salicylic acid is 2,5-dihydroxy benzoic acid and not 2,3-dihydroxy benzoic acid as previously reported. In the presence of the antioxidant ascorbic acid the inhibitory capacity of phytic acid on the generation of reactive oxygen species is completely subverted. Therefore, the kinetics of reactive oxygen species production by faeces is currently under further investigation by high-performance liquid chromatography and chemiluminescence in various patient groups and may give an insight into the role of reactive oxygen species in the aetiology of colorectal cancer.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The wealth of new information about the molecular mechanisms of carcinogenesis that has been obtained over the last decade has generated a variety of new hypotheses about the relationship between diet and cancer. The classical model for the anticarcinogenic effect of cereal fibre is based largely on assumptions about the physical effects of nonstarch polysaccharides within the colonic lumen, and on the putative benefits of faecal bulk. However, the difficulty of studying the disease process directly in human subjects continues to limit our ability to test these hypotheses directly. The role of mutagenesis due to oxygen free radicals in the pathogenesis of human cancers remains largely hypothetical, and attempts to prevent cancer by intervention with high doses of antioxidant vitamins have been largely unsuccessful. Various promising lines of evidence reviewed briefly here do suggest that the presence of substances other than nonstarch polysaccharides in cereal cell walls may at least contribute to the epidemiological relationship between cereal fibre consumption and cancer. Among the various topics reviewed, the intraluminal production of biologically active phenolic compounds and the antioxidant and antiproliferative effects of phytic acid seem particularly worthy of further study in the context of high-fibre cereals.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The strength of the hypothesis that fibre reduces the risk of breast cancer is its biological plausibility, which is supported by experimental and interventional findings and by the coherence of observational studies. However, at least half the available epidemiological studies have failed to show a decreased risk in breast cancer for an increased fibre intake. But intervention studies taking the plasma concentration of oestrogens as an end-point showed significantly lower levels of breast cancer in women with a high-fibre and low-fat diet than in women with usual Western diets. Any reduction in breast cancer risk appears to be significantly dependent on the level of fibre intake. Several explanations can be proposed, including measurement errors in food intake, the insufficiency of food-composition tables, the difficulty of allowing for the diversity of fibre intake and the complexity of the natural history of breast cancer. More research is needed, not only better nutritional surveys for the different types of fibre intake and improvements in food-composition tables, but also epidemiological studies with the power to control for all the eventual confounding risk factors. Although the scientific evidence is not complete, recommendations for a fibre-rich diet should be made, both for cereals and for fruit and vegetables, in part because such diets at least do no harm, but also because fibre is known to be protective against other pathological conditions.

ISSN:0959-8278    

出版商:OVID    

年代:1998

数据来源: OVID