Objective: To describe the relative validity and reliability of the FFQ used for assessing nutrient intakes of participants in the Tehran Lipid and Glucose Study (TLGS). Design: A total of 132 subjects (sixty-one males and seventy-one females) were included in the study. Dietary data were collected monthly by means of twelve 24 h dietary recalls (24hDR). Subjects completed two, 168-item semi-quantitative FFQ. Blood and urine samples were taken every season for measurement of plasma biomarkers and urinary N and K. Results: Mean age and BMI of the participants were 35·5 (sd 16·8) years and 25·5 (sd 5·2) kg/m², respectively. The mean energy-adjusted and deattenuated correlation coefficients for overall nutrient intake between the 24hDR and FFQ2 were 0·44 and 0·37 in ≤35-year-olds and >35-year-olds, respectively, and for individual nutrients ranged from 0·24 to 0·71 in men (mean r = 0·53) and from 0·11 to 0·60 in women (mean r = 0·39). The mean energy-adjusted reliability coefficients varied from 0·48 in ≤35-year-olds to 0·65 in >35-year-olds, and ranged from 0·41 to 0·79 in men (mean r = 0·59) and from 0·39 to 0·74 in women (mean r = 0·60). The FFQ2 and 24hDR produced exact agreement rates ranging between 39·6 % and 68·3 % in men and between 39·6 % and 54·1 % in women. The ranges of questionnaire validity coefficients, with the sample correlation between the questionnaires and biochemical marker as the lower limit and the estimate obtained by the method of triads as the upper limit, were 0·21–0·56 (protein) and 0·37–0·61 (K). Conclusions: The FFQ developed for the TLGS has reasonable relative validity and reliability for nutrient intakes in Tehranian adults.

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The aim of the present study was to assess the reliability, comparative validity and stability of dietary patterns defined by factor analysis for participants of the Tehran Lipid and Glucose Study. A total of 132 subjects, aged ≥ 20 years, completed a 168-item FFQ (FFQ1, FFQ2) twice, with a 14-month interval. Over this duration, twelve dietary recalls (DR) were collected each month. To assess the stability of the FFQ, participants completed the third FFQ (FFQ3) after 8 years. Following these, two dietary patterns – the ‘Iranian Traditional’ and the ‘Western’ – were derived from FFQ1 and FFQ2 and the mean of DR (mDR); and three dietary patterns were identified from FFQ3: the ‘Iranian Traditional’, the ‘Western’ and the ‘Combined’. The reliability correlations between factor scores of the two FFQ were 0·72 for the Iranian Traditional and 0·80 for the Western pattern; corrected month-to-month variations of DR correlations between the FFQ2 and mDR were 0·48 for the first and 0·75 for the second pattern. The 95 % limits of agreement for the difference between factor scores obtained from FFQ2 and mDR lay between − 1·58 and +1·58 for the Iranian Traditional and between − 1·33 and +1·33 for the Western pattern. The intra-class correlations between FFQ2 and FFQ3 were − 0·09 (P = 0·653) and 0·49 (P <0·001) for the ‘Iranian Traditional’ and the ‘Western’, respectively. These data indicate reasonable reliability and validity of the dietary patterns defined by factor analysis. Although the Western pattern was found to be fairly stable, the Iranian Traditional pattern was mostly unstable over the 8 years of the study period.

Cardiovascular disease (CVD), as the leading cause of death worldwide, is the collective term named for disorders afflicting the blood vessels and heart. Inflammation and enhanced oxidative stress have been shown as fundamental risk factors in the onset and progression of CVD. Chronic inflammatory conditions attenuate blood levels of antioxidants because of the continuous generation of elevated levels of reactive oxygen species (ROS). A sufficient intake of antioxidants is also suggested to beneficially interfere with CVD by quenching ROS. Antioxidant vitamins and minerals, such as vitamins A, E, and C, and zinc may slow the development and progression of CVD. This study aimed at investigating the association between daily consumption of dietary vitamins A, E, and C, and zinc and the incidence of CVD. Eligible adults (n = 5102) aged ≥ 30 years, were selected from the participants of the Tehran lipid and glucose study with an average follow-up of 5.3 years. Dietary intake was assessed using a valid and reliable semi-quantitative food frequency questionnaire. Anthropometrics and biochemical variables were evaluated at baseline and follow-up examinations. Multivariable Cox proportional hazard regression models were used to estimate the development of CVD associated with total intakes of vitamins A, E, and C, and zinc. This study was conducted on 2253 men and 2849 women aged 47.0 ± 11.6 and 45.6 ± 10.5 years, respectively. The main sources of dietary vitamins A, E, and C and zinc were fruits, vegetables, and legumes. Risk of CVD decreased from quartile 1 to quartile 4 for vitamin E intake (HR 1.00, 0.91, 0.77, and 0.57; P_trend = 0.03). The association between the risk of CVD and quartiles of vitamins A, and C and zinc intake was not statistically significant. Our study suggests an inverse association between vitamin E intake and the risk of CVD, emphasizing the potential protective role of fruit and vegetable in the prevention of CVD.

Refined grains and white rice have been associated with elevated risk of type 2 diabetes mellitus (T2DM). In this study, we sought to quantify the effect of white rice intake on incident T2DM in two prospective population-based cohort studies from Iran, where white rice is one of the main staple. We used follow-up data from 9,182 participants from Golestan Cohort Study (GCS, 2004–2007, conducted mainly in rural areas) and 2,173 from Tehran Lipid and Glucose Study (TLGS, 2004–2006) who did not have T2DM and other chronic diseases at baseline. Diet was assessed using validated food frequency questionnaires. Multivariable logistic regression models were used to estimate adjusted odds ratios (ORs) for incident T2DM. We documented 902 new cases of T2DM in GCS and 81 in TLGS. Age-standardized cumulative incidence of T2DM was 9.9% in Golestan and 8.0% in Tehran. Daily white rice intake was significantly higher among residents of Tehran compared to Golestan (median daily intake: 250 vs. 120 grams; P-value < 0.001). After adjustment for potential confounders, there was no significant association between daily white rice intake and incident T2DM in GCS. In TLGS, the adjusted OR (95% confidence interval (CI)) was 2.1 (1.1, 3.9) comparing participants with daily white rice intake of >250 grams/day to those with <250. We observed an increased lieklihood of T2DM associated with high white rice intake among residents of Tehran and no association in Golestan. Our findings, if further supported by other studies, have important public health implications especially for countries where white rice is a major staple and diabetes is increasing rapidly incidence is high. Further research is needed to investigate lack of an association between lower levels of white rice intake and T2DM.