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Background Dietary assessment is complex, and strategies to select the most appropriate dietary assessment tool (DAT) in epidemiological research are needed. The DIETary Assessment Tool NETwork (DIET@NET) aimed to establish expert consensus on Best Practice Guidelines (BPGs) for dietary assessment using self-report. Methods The BPGs were developed using the Delphi technique. Two Delphi rounds were conducted. A total of 131 experts were invited, and of these 65 accepted, with 48 completing Delphi round I and 51 completing Delphi round II. In all, a total of 57 experts from North America, Europe, Asia and Australia commented on the 47 suggested guidelines. Results Forty-three guidelines were generated, grouped into the following four stages: Stage I. Define what is to be measured in terms of dietary intake (what? who? and when?); Stage II. Investigate different types of DATs; Stage III. Evaluate existing tools to select the most appropriate DAT by evaluating published validation studies; Stage IV. Think through the implementation of the chosen DAT and consider sources of potential biases. Conclusions The Delphi technique consolidated expert views on best practice in assessing dietary intake. The BPGs provide a valuable guide for health researchers to choose the most appropriate dietary assessment method for their studies. These guidelines will be accessible through the Nutritools website, www.nutritools.org. Electronic supplementary material The online version of this article (doi:10.1186/s12916-017-0962-x) contains supplementary material, which is available to authorized users.

Item does not contain fulltext Carotenoids and vitamins A, C and E are possibly associated with a reduced colorectal cancer (CRC) risk through antioxidative properties. The association of prediagnostic plasma concentrations and dietary consumption of carotenoids and vitamins A, C and E with the risk of colon and rectal cancer was examined in this case-control study, nested within the European Prospective Investigation into Cancer and Nutrition study. Plasma concentrations of carotenoids (alpha- and beta-carotene, canthaxanthin, beta-cryptoxanthin, lutein, lycopene, zeaxanthin) and vitamins A (retinol), C and E (alpha-, beta- and gamma- and delta-tocopherol) and dietary consumption of beta-carotene and vitamins A, C and E were determined in 898 colon cancer cases, 501 rectal cancer cases and 1,399 matched controls. Multivariable conditional logistic regression models were performed to estimate incidence rate ratios (IRR) and corresponding 95% confidence intervals (CIs). An association was observed between higher prediagnostic plasma retinol concentration and a lower risk of colon cancer (IRR for highest quartile = 0.63, 95% CI: 0.46, 0.87, p for trend = 0.01), most notably proximal colon cancer (IRR for highest quartile = 0.46, 95% CI: 0.27, 0.77, p for trend = 0.01). Additionally, inverse associations for dietary beta-carotene and dietary vitamins C and E with (distal) colon cancer were observed. Although other associations were suggested, there seems little evidence for a role of these selected compounds in preventing CRC through their antioxidative properties.

Background: Diet, lifestyle and heritable factors have been related to colorectal cancer risk; to date, their relevance to the overall scope of colorectal carcinogenesis, has not been clearly established.Aim and Methods: To evaluate whether distinguishing colorectal tissue by its histopathological and molecular characteristics sheds further light on the etiology of colorectal cancer. Five research questions addressed associations between diet, lifestyle and heritable factors, and specific tissue characteristics.Results: First, we observed that consumption of fruits, in particular citrus fruits, was associated with increased rectal glutathione S-transferase activity in a cross-sectional study of 94 Dutch individuals. Consumption of cruciferous vegetables was also associated with increased activity, but only among individuals who carried the GSTM1 genotype.Second, we observed that intake of vitamin B2 was inversely associated with adenomas with a K-ras mutation (n=81) but not with adenomas without a K-ras mutation (n=453) in a case-control study conducted in the Netherlands. A positive association with monounsaturated fat was confined to K-ras mutation-negative adenomas. We found indications for differential associations with some additional factors, but the epidemiological evidence on risk factors and K-ras mutations remains inconsistent.Third, in a cohort study of 26,769 American men, we observed that most risk factors were similarly associated with advanced (=1cm or with any villous characteristics or carcinoma in situ) and non-advanced colorectal adenomas after 17 years of follow-up. However, smoking had a stronger positive association with advanced adenomas than with non-advanced adenomas, and ahigh glycemic index was inversely associated with advanced but not with non-advanced adenomas.Fourth, associations with family history of colorectal cancer were stronger for men with multiple distal adenomas than for men with a single distal adenoma at first diagnosis, in the aforementioned cohort study among US men. Associations between family history, and advanced and non-advanced adenomas, were of similar strength, but a tendency towards a somewhat stronger association with non-advanced adenomas was found.Fifth, fruit consumption was inversely associated with hMLH1 protein-deficient colon cancer (n=54) but not with hMLH1 protein-proficient colon cancer (n=387) in a cohort study of 120,852 people who were followed-up over 7.3 years, while ignoring information from the initial 2.3 years of follow-up. Clear associations with consumption of vegetables, or nutrients related to fruits and vegetables, could not be detected.Conclusions: We showed that distinguishing colorectal tumors by their histopathological and molecular characteristics may indeed shed further light on the role of diet, lifestyle and heritable factors in colorectal carcinogenesis. Such an approach may alleviate some of the weaknesses of traditional epidemiology, but also adds another layer of complexity. It is a challenge for the future to develop a framework into which specific associations can be integrated, using risk markers signaling the molecular and biochemical pathways from normal to cancerous tissue.