Journal of The American Dietetic Association最新文献

Green tea catechins (GTCs) have been studied in randomized control trials for their lipid-lowering effects. Studies, however, have been small and demonstrated conflicting results. The objective of this study was to perform a systematic review and meta-analysis of randomized controlled trials evaluating the relationship between GTCs and serum lipid levels, including total, low-density lipoprotein (LDL), high-density lipoprotein (HDL) cholesterol, and triglycerides. A systematic literature search of MEDLINE, EMBASE, Cochrane CENTRAL, and the Natural Medicines Comprehensive Database was conducted through March 2010. Randomized controlled trials evaluating GTCs vs control in human beings and reporting efficacy data on at least one of the aforementioned serum lipid endpoints were included. Weighted mean differences for changes from baseline (with 95% confidence intervals [CIs]) for lipid endpoints were calculated using random-effects models. Twenty trials (N=1,415) met all inclusion criteria. Upon meta-analysis, GTCs at doses ranging from 145 to 3,000 mg/day taken for 3 to 24 weeks reduced total (−5.46 mg/dL [−0.14 mmol/L]; 95% CI −9.59 to −1.32) and LDL cholesterol (−5.30 mg/dL [−0.14 mmol/L]; 95% CI −9.99 to −0.62) compared to control. GTCs did not significantly alter HDL cholesterol (−0.27 mg/dL [−0.007 mmol/L]; 95% CI −1.62 to 1.09) or triglyceride (3.00 mg/dL [−0.034 mmol/L]; 95% CI −2.73 to 8.73) levels. The consumption of GTCs is associated with a statistically significant reduction in total and LDL cholesterol levels; however, there was no significant effect on HDL cholesterol or triglyceride levels.

Background

There is no consensus as to whether low dietary intakes of saturated fat or cholesterol, or high intakes of dietary fiber are related to a lower prevalence of metabolic syndrome (MetS) in adolescent children.

Objective

To determine whether a fiber-rich diet as measured by a fiber index (grams fiber/1,000 kcal) is associated with lower rates of MetS among adolescents vs a diet low in saturated fat or cholesterol as measured by a saturated fat index (grams saturated fat/1,000 kcal) and a cholesterol index (milligrams cholesterol/1,000 kcal), respectively.

Design/participants/setting

Cross-sectional analysis of 12- to 19-year-old boys and girls (N=2,128) who participated in the National Health and Nutrition Examination Survey 1999-2002.

Outcomes and statistical analyses

The prevalence of MetS (abnormal values of three or more of the following: waist circumference, blood pressure, fasting serum high-density lipoprotein cholesterol, triglycerides, and glucose) was compared across quintiles of the dietary indexes (fiber index, saturated fat index, and cholesterol index) derived from 24-hour recalls. χ² tests determined the prevalence across dietary quintiles, and multivariate logistic regression evaluated the association of the dietary indexes with MetS. Weighted analyses were used controlling for sex, age, ethnicity, and family income. Significance was set at P≤0.05.

Results

The overall prevalence of MetS was 6.4% (n=138). There was a graded inverse association between the fiber index and MetS (P<0.001) with a threefold difference between the lowest and highest quintiles (9.2% vs 3.1%). Each quintile increase in the fiber index was associated with a ∼20% decrease in MetS (adjusted odds ratio 0.83, 95% confidence interval 0.68-1.00; P≤0.043). Neither the saturated fat index (P=0.87) nor the cholesterol index (P=0.22) was significantly associated with MetS.

Conclusions

Higher intakes of dietary fiber, but not low intakes of saturated fat or cholesterol are related to the MetS in adolescents. These findings suggest that to reduce the risks for MetS in adolescents, it is more important to emphasize a paradigm that promotes the inclusion of fiber-rich, nutrient-dense, plant-based foods vs what foods to restrict or exclude as is commonly done when the focus is on total fat, cholesterol, or saturated fat intake.