2016年7月16日 訊 /生物谷BIOON/ --不知道大家有沒有關注過超市某一條通道旁邊寫著"健康食品"的標牌，如果有的話，那麼貨架上擺放的大概就是低脂、富含纖維素的零食了。
不過問題來了，低脂食品可能並不能達到健康的效果。
多年的研究似乎證明了這一觀點。一項囊括50000名女性，長達8年的研究表明：大約有一半的女性選擇低脂飲食，但這一飲食方式並不能降低她們患乳腺癌，結腸癌以及心臟病的風險。此外，她們的體重也沒有明顯的減低。
不過，針對從特定類型的脂肪或纖維素中獲取的卡路裡究竟對人體有何不同的影響還沒有充分的研究。
最近發表在《JAMA》雜誌上的一篇文章表明糖分，而非脂肪，是問題的關鍵。
這並不奇怪，幾十年的研究已經表明糖分是增加體重的關鍵，糖分的攝入變化能夠引發血糖的劇烈升高或降低，這一平衡的破壞會引發機體的不適感，即人們會表現出生氣同時以及飢餓感。
所有的碳水化合物食品，包括麵包、麥片以及土豆，都會最終分解成為葡萄糖，它會在我們血液系統中循環並提供能量。根據CDC的說法，美國人攝入的大部分卡路裡都來自於加工食品，比如麥片、燕麥卷、麵包以及蛋糕。
另外，不同類型的脂肪並不會等量的生成。
在一項最近的研究中，作者們通過調查問卷的方式分析了126000名志願者三十年來的飲食習慣。之後，他們嘗試將這些志願者的飲食中飽和脂肪酸（主要存在於肉類與奶類食品中）提供的5%的能量替換為別的營養類型：1、簡單碳水化合物，如葡萄糖或加工穀類食品；2、單不飽和脂肪酸，比如牛油果或橄欖油；3、多聚不飽和脂肪酸，比如魚類與堅果。
理所當然地，第一種替換方式沒有起到任何的促健康效應。
但第二種與第三種方式似乎能夠起到一定的促進健康的效果。第二種替換方式能夠有效降低27%的死亡率，心臟病、癌症與神經退行性疾病的發病風險也發生了明顯的降低。
第三種替換方式能夠降低13%的死亡率，神經退行性疾病引發的死亡風險也有明顯降低。
"不同類型的脂肪存在差異"，該研究的首席作者，來自哈佛大學的營養學家Frank B. Hu說道。換句話說，某些類型的脂肪也許比別的脂肪類型更加有好處。"我們應該多吃點魚類以及牛油果，少吃動物食品"。
這一研究結果與近期一些別的研究結論一致，即某些類型的脂肪是由促進健康的作用的，只要我們適當地攝入。(生物谷bioon.com）
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doi:10.1001/jamainternmed.2016.2417
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Association of Specific Dietary Fats With Total and Cause-Specific Mortality ONLINE FIRST
Dong D. Wang, MD, MSc; Yanping Li, PhD; Stephanie E. Chiuve, ScD; Meir J. Stampfer, MD, DrPH; JoAnn E. Manson, MD, DrPH; Eric B. Rimm, ScD; Walter C. Willett, MD, DrPH; Frank B. Hu, MD, PhD
Importance Previous studies have shown distinct associations between specific dietary fat and cardiovascular disease. However, evidence on specific dietary fat and mortality remains limited and inconsistent.
Objective To examine the associations of specific dietary fats with total and cause-specific mortality in 2 large ongoing cohort studies.
Design, Setting, and Participants This cohort study investigated 83?349 women from the Nurses' Health Study (July 1, 1980, to June 30, 2012) and 42?884 men from the Health Professionals Follow-up Study (February 1, 1986, to January 31, 2012) who were free of cardiovascular disease, cancer, and types 1 and 2 diabetes at baseline. Dietary fat intake was assessed at baseline and updated every 2 to 4 years. Information on mortality was obtained from systematic searches of the vital records of states and the National Death Index, supplemented by reports from family members or postal authorities. Data were analyzed from September 18, 2014, to March 27, 2016.
Main Outcomes and Measures Total and cause-specific mortality.
Results During 3439954 person-years of follow-up, 33?304 deaths were documented. After adjustment for known and suspected risk factors, dietary total fat compared with total carbohydrates was inversely associated with total mortality (hazard ratio [HR] comparing extreme quintiles, 0.84; 95% CI, 0.81-0.88; P?<?.001 for trend). The HRs of total mortality comparing extreme quintiles of specific dietary fats were 1.08 (95% CI, 1.03-1.14) for saturated fat, 0.81 (95% CI, 0.78-0.84) for polyunsaturated fatty acid (PUFA), 0.89 (95% CI, 0.84-0.94) for monounsaturated fatty acid (MUFA), and 1.13 (95% CI, 1.07-1.18) for trans-fat (P?<?.001 for trend for all). Replacing 5% of energy from saturated fats with equivalent energy from PUFA and MUFA was associated with estimated reductions in total mortality of 27% (HR, 0.73; 95% CI, 0.70-0.77) and 13% (HR, 0.87; 95% CI, 0.82-0.93), respectively. The HR for total mortality comparing extreme quintiles of ω-6 PUFA intake was 0.85 (95% CI, 0.81-0.89; P?<?.001 for trend). Intake of ω-6 PUFA, especially linoleic acid, was inversely associated with mortality owing to most major causes, whereas marine ω-3 PUFA intake was associated with a modestly lower total mortality (HR comparing extreme quintiles, 0.96; 95% CI, 0.93-1.00; P?=?.002 for trend).
Conclusions and Relevance Different types of dietary fats have divergent associations with total and cause-specific mortality. These findings support current dietary recommendations to replace saturated fat and trans-fat with unsaturated fats.