Association between dietary antioxidant capacity and type 2 diabetes mellitus in Chinese adults: a population-based cross-sectional study
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Abstract Background Higher intakes of dietary antioxidants have been linked to a lower type 2 diabetes mellitus (T2DM) risk. However, few studies have comprehensively examined the overall dietary antioxidant capacity, assessed by dietary antioxidant quality scores (DAQS) and dietary total antioxidant capacity (DTAC), related to T2DM risk, especially in populations consuming relatively monotonous diets. This study aimed to evaluate the associations of DAQS, DTAC, and T2DM among rural Chinese adults. Methods Data from 12,467 participants from the Natural Population Cohort of Northwest China: Ningxia Project was analyzed. Dietary intake was assessed using a validated semi-quantitative food frequency questionnaire. DAQS were calculated based on vitamins A, C, and E, zinc (Zn), and selenium (Se) intake. DTAC was estimated using the ferric-reducing ability of plasma assay. Logistic regression models were used to evaluate the associations of DAQS and DTAC with T2DM risk. Restricted cubic splines were used to assess potential non-linear relationships between DTAC and T2DM. Results T2DM was observed in 1,238 (9.9%) participants. After adjusting for confounders, compared to the lowest tertiles (T1) of DAQS, the odds ratios (ORs) for T2DM were 1.03 (95% CI 0.82–1.30) in T2 and 0.85 (95% CI 0.68–1.06) in T3 ( P = 0.010). Compared to T1, the ORs for T2DM in the highest T3 were 0.78 (95% CI 0.67–0.91, P-trend = 0.008) for vitamin A, 1.34 (95% CI 1.15–1.56, P-trend < 0.001) for vitamin E, 0.83 (95% CI 0.71–0.97, P-trend = 0.007) for Se, and 0.86 (95% CI 0.74–1.01, P-trend = 0.033) for Zn. Compared to the lowest quartile(Q1) of DTAC, the OR in the highest Q4 was 0.96 (95% CI 0.80–1.17, P-trend = 0.024) for T2DM. A non-linear relationship was observed between DATC and T2DM. Conclusion Higher DAQS and DATC were associated with a lower T2DM risk, suggesting that consuming antioxidant-rich foods may reduce the T2DM risk.Keywords:
Clinical nutrition
Cross-sectional study
Extracts of ginger contain a great number of substances having antoxidant activity. This reaserch was conducted to study the effect of ginger on malonaldehyde (MDA) as indicator of free radical and vitamin E as one of the nutrient antioxidants. Healthy student subjects were divided into treated (n=12) and control group (n=12). Treated group was suplemented with ginger drink for 30 days. At the beginning and the end of intervention, both treatment and control groups were subjected to physical health examination and their peripheral blood were with drawn for analysis of MDA (malonaldehyde) and vitamin E in plasma. Individual data from all groups revealed that treated group has significant decrease of MDA and increase of vitamin E (p<0,01) compare to the control group.The result of this researh revealed that ginger drink has a potent antioxidant activity to decrease MDA and increase vitamin E, level in the plasma.
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Clinical nutrition
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Effect modification
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Confounding may be present in nonrandomized etiological research involving human populations. It can result in erroneous conclusions about the effect of exposure on a disease outcome or about any form of causality between predictors and outcomes. Confounding can wholly or partially account for the apparent effect of the risk factor under consideration or mask the underlying, true association. Not controlling for the effects of confounding can lead to biased results, thus compromising the validity of study conclusions. The three goals of this article are: (1) to define a confounder or a confounding variable, (2) to discuss strategies for controlling the effects of confounding, and (3) to illustrate the perverse effects of confounding with the help of an example.
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Abstract: Hemodialysis deteriorates oxidative stress. Vitamin E is an antioxidant whose regeneration is provided for by vitamin C. The authors tested the effects of a vitamin E‐modified membrane (E), nonmodified cellulose membrane (O), and vitamin C infusion (500 mg, C) into the arterial blood line during dialysis on parameters of oxidative stress. In a short‐term study, 24 patients were subjected to a single dialysis session with E, O, E with C, and O with C protocols. In a long‐term study (12 weeks), 20 patients were randomized into groups with C and without C on each dialysis, and both groups had dialysis using O, E, and again O membrane for 4 weeks each. In the short‐term study, thiobarbituric acid reacting substances (TBARS) in plasma rose after dialysis (p < 0.02) with O, and no changes were observed in the other 3 protocols. In the long‐term study, predialysis TBARS declined when using E both in the groups with C (p < 0.02) and without C (p < 0.05). A switch over to O resulted in TBARS returning to baseline levels. The E membrane prevented an increase in lipid peroxidation during single dialysis, and long‐term use of the E membrane also resulted in a decrease in the predialysis lipid peroxidation level. The antioxidant capacity of the E membrane was not enhanced by vitamin C infusion. High doses of vitamin C administered during dialysis using a nonmodified cellulose membrane prevented an increase in lipid peroxidation, most probably due to the enhanced rate of endogenous vitamin E regeneration.
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The antioxidant effects of vitamins C and E on cryptorchidism-induced oxidative stress were investigated in male Sprague-Dawley rats. Forty rats (200-250 g) were randomly divided in a blinded fashion into five groups (n = 8). Group 1 was sham operated and treated with vehicle (corn-oil, 10 mL/kg). Groups 2, 3, 4, and 5 were rendered unilaterally cryptorchid and treated with vehicle (10 mL/kg), vitamin E solution (75 mg/kg), vitamin C solution (1.25 g/kg), and combination of vitamin E (75 mg/kg) and vitamin C (1.25 g/kg) solutions, respectively. Germ cell count, superoxide dismutase (SOD), total protein (TP), and testicular weight (TW) were lower, but malondialdhyde (MDA) was higher in the cryptorchid rats than the sham-operated rats. When administered separately, vitamins C and E increased germ cell count, SOD, TP, and TW but did not reduce MDA in the cryptorchid rats when compared to the vehicle-treated cryptorchid rats. However, there was no significant difference in these parameters between vehicle-treated and combined vitamins C- and E-treated rats. This suggests that vitamins E and C alleviate the germ cell loss and oxidative stress in cryptorchidism when administered separately but not when combined in rats.
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Abstract The first part of this chapter discusses the conditions under which a factor can confound the association between exposure and disease, and the conditions under which this cannot occur. It also differentiates confounders from antecedents or mediators. The next part discusses methods devised to neutralize the effects of confounders. Two standard methods are presented: matching to prevent confounding in the data by equalizing the exposed and the unexposed on a potential confounder, and statistical adjustment to compensate for confounding in the data by separating the effects of the exposure from the effects of the confounder.
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Abstract Confounding biases study results when the effect of the exposure on the outcome mixes with the effects of other risk and protective factors for the outcome that are present differentially by exposure status. However, not all differences between the exposed and unexposed group cause confounding. Thus, sources of confounding must be identified before they can be addressed. Confounding is absent in an ideal study where all of the population of interest is exposed in one universe and is unexposed in a parallel universe. In an actual study, an observed unexposed population represents the unobserved parallel universe. Thinking about differences between this substitute population and the unexposed parallel universe helps identify sources of confounding. These differences can then be represented in a diagram that shows how risk and protective factors for the outcome are related to the exposure. Sources of confounding identified in the diagram should be addressed analytically and through study design. However, treating all factors that differ by exposure status as confounders without considering the structure of their relation to the exposure can introduce bias. For example, conditions affected by the exposure are not confounders. There are also special types of confounding, such as time‐varying confounding and unfixable confounding. It is important to evaluate carefully whether factors of interest contribute to confounding because bias can be introduced both by ignoring potential confounders and by adjusting for factors that are not confounders. The resulting bias can result in misleading conclusions about the effect of the exposure of interest on the outcome.
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