鎂、膳食纖維，還是富含這些營養素的食物有利於降低糖尿病的風險?

Abstract

研究目的: 動物實驗與流行病學研究顯示，鎂攝取量不足可能會影響胰島素作用 以及第二型糖尿病的發生，本研究的目的首先在於釐清鎂攝取量、血漿鎂濃度以及尿液鎂排出量三項指標之間的相關性。其次則是以前瞻性研究法分析鎂營養狀況或不同的營養素攝取型態與後來發生第二型糖尿病的危險性，以期了解到底是鎂，還是與鎂相關之飲食成份，組合式的降低疾病風險。 材料與方法: 本研究使用「竹東及朴子地區心臟血管疾病長期追蹤研究」五次循環所收集的資料進行分析，首先以第一循環的3897人與第二循環的4836人分析鎂營養狀況的飲食、血液、尿液指標值，觀察性別、年齡別差異、三指標之間的相關性以及兩項生化指標與腎功能的相關性。在前瞻性分析中，以第二循環為基線，選取30歲以上、不曾罹患糖尿病、心血管疾病、中風或癌症的個案共1334人的資料，使用Cox’s model調整多變數，估計鎂營養狀況或其他營養素攝取不同時，發生糖尿病的相對危險性。最後則是使用因素分析，將飲食頻率問卷估計出的19種營養素攝取量減少為數個因子，分析營養素攝取型態與糖尿病之間的關係。 研究結果: 飲食鎂攝取量與尿液鎂/肌酸酐比值有顯著但低度的正相關(r = 0.076, p=0.0008)。而血漿鎂濃度與尿液鎂/肌酸酐比值分別和血漿肌酸酐濃度呈現顯著正相關與逆相關，推測這兩項生化指標有可能部份反映腎功能。而經過調整年齡、性別、肥胖、抽煙飲酒習慣、運動習慣、家族糖尿病史、高血壓、高血糖與血脂異常等因子之後，鎂攝取量四分位組中較低的三組發生糖尿病的危險性都顯著高於最高組。而尿液鎂/肌酸酐比值與發生胰島素阻抗危險性也呈現顯著但幅度略低的逆相關。根據各種營養素攝取量經過因素分析找出四個因素，因素一剛好包含鎂、膳食纖維及鉀攝取量，因素三包含膳食纖維和鉀，兩者均與發生糖尿病危險性呈顯著逆相關。而膳食纖維、鉀攝取量單獨與糖尿病危險性呈現顯著逆相關，且膳食纖維的相關幅度超越鉀以及因素一、因素三。 結論: 本研究結果顯示鎂營養狀況不良可能低度顯著的增加胰島素抗性，但不影響糖尿病發生率；而多攝食富含鎂、膳食纖維和鉀的食物，特別是富含膳食纖維的食物，才能降低發生糖尿病的風險。不過到底是膳食纖維還是其他食物成分或各種有益成份之組合所呈現之效果，還有待進一步之探討。

Objective: Animal experiments and epidemiological studies suggested that insufficient Mg intake may have a negative effect on the action of insulin and the incidence of type 2 diabetes. The first objective of this study was to investigate the relationships between dietary Mg intake, plasma Mg concentration and urinary Mg/creatinine ratio. The second purpose was to prospectively evaluate the associations between Mg status or different nutrient intake patterns and incidence of insulin resistance and type 2 diabetes, to further understand whether magnesium or combination of nutrient / food component inadequacy correlate with magnesium reduce the risk of developing diabetes Method: This study analyzed data collected from the 5 cycles of the Cardiovascular Disease Risk Factor Two Township Study. First, we used data from 3897 subjects at Cycle 1 and from 4836 subjects at Cycle 2 to analyze the relationships between dietary, plasma and urinary magnesium indices. We described the sex difference and age trend of each index and the associations between the two biological Mg indices and kidney function. In the prospective analysis, the individual profile at Cycle 2 was taken as baseline. A cohort of 1334 subjects aged ≧ 30 years with no previous history of diabetes, cardiovascular disease, stroke or cancer were followed for the next three cycles. Cox’s proportional hazard model was used to estimate multivariate relative risks (RRs) of type 2 diabetes and insulin resistance across different levels of Mg status or nutrient intake. In addition, we used factor analysis to extract nutrient intake factors and relate these factors to incidence of diseases. Result: Urinary Mg/creatinine ratio had a significant, but small positive correlation with dietary Mg intake. Plasma Mg concentration and urinary Mg/creatinine ratio were positively and negatively correlated with plasma creatinine concentration, respectively; suggesting that the two biological indices may partly reflect kidney function. The multivariate-adjusted RRs of diabetes was significantly higher in the lower three quartiles than the highest quartile of dietary Mg intake. Urinary Mg/creatinine ratio had a significant inverse correlation with risk of insulin resistance. Four factors were extracted from factor analysis. Factor 1 included intake of magnesium, dietary fiber, and potassium. Factor 3 included intake of dietary fiber and potassium. Both factor 1 and 3 had significant inverse associations with risk of diabetes. However, intake of dietary fiber and potassium also had significant inverse associations with risk of diabetes separately. The effect of dietary fiber was greater than that of potassium, factor 1 and factor 3. Conclusion: These findings support a moderate protective role of magnesium status on developing insulin resistance, but not on diabetes incidence. Foods rich in magnesium, dietary fiber and potassium, especially food rich in dietary fiber reduced the risk of developing type 2 diabetes. Whether the effect came from dietary fiber, other food components or a combination of several beneficial components requires further research.