低碳水化合物飲食對心血管危險因子之影響：整合分析

Abstract

研究背景 低碳水化合物飲食近年來由於減重風潮而逐漸受到關注，然而研究證據對該飲食影響減重及改善心血管危險因子之利弊仍模糊不清。因此本研究欲利用整合分析探討低碳水化合物飲食對體重、血液脂肪、空腹血糖及血壓之影響，並用整合回歸釐清該飲食中熱量與營養素影響心血管危險因子變化之效應。 材料方法 PUBMED搜尋1998/1/1∼2006/12/31低碳水化合物飲食之隨機試驗中設立對照組且有飲食資料及至少一項心血管危險因子者。由兩位研究者獨立萃取研究特性、飲食變項與結果指標後，進行整合分析、整合回歸及趨勢面分析。 研究結果 21篇納入整合分析之研究顯示，低碳水化合物飲食組體重下降較對照組多（加權平均-1.6公斤，95％信賴區間-2.8∼-0.4公斤）。三酸甘油酯（加權平均-0.25mmol/L，95%信賴區間-0.32∼0.18 mmol/L）及高密度脂蛋白膽固醇（加權平均0.1mmol/ L，95%信賴區間0.06∼0.15mmol/L）變化在低碳水化合物組有較好影響；但總膽固醇（加權平均0.12 mmol/L，95%信賴區間0.05∼0.41mmol/L）及低密度脂蛋白膽固醇（加權平均0.28mmol/L，95%信賴區間0.14∼0.42mmol/L）則在控制組效應較佳。整合回歸指出，單一營養素與結果指標變化無顯著相關。趨勢面分析則發現，「低碳水化合物、較高蛋白質與高脂肪」之營養素組合對體重、高密度脂蛋白膽固醇及三酸甘油酯有改善；「高碳水化合物與低脂肪」攝取則對總膽固醇與低密度脂蛋白膽固醇變化有較好影響。 結論 相較於「低脂肪且熱量不足」飲食，「低碳水化合物，較高蛋白質且高脂肪」組合減重與改善三酸甘油酯、高密度脂蛋白膽固醇效果較顯著，但對總膽固醇及低密度脂蛋白膽固醇有不良影響。未來需進一步以試驗性研究，探討是否調整脂肪酸比例使此組合之效應達到更為理想的狀態。

Background Attention on low-carbohydrate diets is increasing with the popularity of weight loss. However, trials showed contradictory results on benefits and risks of these diets to achieve weight loss and modify cardiovascular risk factors. The objective of this meta-analysis was to determine the effect of low-carbohydrate diets on weight, serum lipids, fasting glucose, and blood pressure. In addition, meta-regression was applied to characterize the components of low-carbohydrate diets that affect changes in cardiovascular risk factors. Methods PUBMED engine was used for searching literatures about low-carbohydrate diets published between January 1, 1998 and December 31, 2006. We selected articles which recruited control groups and presented diet contents and at least one of the cardiovascular risk factors. After characteristics of study, diet variables, and outcome were independently abstracted by two researchers, meta-analysis, meta-regression, and trend surface analysis were done. Results 21 studies which included in meta-analysis showed low-carbohydrate diets group lose more 1.6kg (95%CI, 0.4~2.8kg) of weight than the control group. Triglycerides (weighted difference in changes, -0.25mmol/L; 95%CI, -0.32 to -0.18mmol/L) and high-density lipoprotein cholesterol (weighted difference in increment, +0.1mmol/L; 95%CI, +0.06 to +0.15mmol/L) levels changed more favorably in individuals assigned to low-carbohydrate diets, but total cholesterol (weighted difference in changes, 0.12mmol/L; 95%CI, 0.05 to 0.41mmol/L) and low-density lipoprotein cholesterol (weighted difference in changes, 0.28mmol/L; 95%CI, 0.14 to 0.42mmol/L) values changed more favorably in individuals assigned to control group. The results of meta-regression indicated that no single macronutrient by itself contributed to the outcomes. Contrarily it is the macronutrient combination of “low-carbohydrate, moderate protein, and high-fat” that betters weight, high-density lipoprotein cholesterol and triglycerides, according to trend surface analysis. Intakes of “high-carbohydrate and low-fat” tend to reduce total cholesterol and low-density lipoprotein cholesterol. Conclusion Compared with ”low-fat and energy-deficit” diets, combination of “low-carbohydrate, moderate protein, and high-fat” showed effects on losing weight, reducing triglycerides, increasing high-density lipoprotein cholesterol, as well as raising low-density lipoprotein cholesterol level. Future studies with experimental designs might be needed to investigate the best ratios of different fatty acid contents in the “low-carbohydrate, moderate protein, and high-fat” diets in order to achieve a favorable cardiovascular profile.