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A study published in the British Journal of Nutrition shows that the nutrient combination of calcium and milkfat present in dairy may play a key role in reducing fat absorption and may have the ability to maintain good cholesterol (HDL) while minimizing any increase in bad cholesterol (LDL). The study, designed to explore why dairy products containing saturated fat and high contents of calcium do not seem to significantly affect blood cholesterol levels as much as saturated fat from other sources, lends credence to the notion that milk and other dairy products with a high content of calcium such as cheese, might actually reduce the risk for cardiovascular disease.
The authors noted that, historically, intervention studies have pointed to a relationship between a diet high in saturated fat and increases in total cholesterol and LDL cholesterol. As a result, some nutrition experts have recommended that consumers limit the intake of high-fat dairy products. However, observational studies have found an inverse relation between intake of milk and other dairy products with a high content of calcium and incidence of cardiovascular disease. The researchers aimed to study whether the high calcium content of dairy products influences the effect of dairy fat on the lipid profile.
The study was a small, clinical trial that included nine participants completing four separate diets over a period of 10 days, with each diet differing in the amount of calcium and fat content. Blood variables were measured before and after each diet period, and feces and urine were collected at the end of each diet period. A two-way analysis of variance (ANOVA) was used to examine the effect of calcium and fat intake. Independent of calcium intake, the high-fat diet increased the concentrations of total, LDL, and HDL cholesterol compared with the low-fat diet. However, independent of fat intake, the high calcium diet decreased the concentrations of total and LDL cholesterol, but not HDL cholesterol compared with the low calcium diet. In addition, total:HDL cholesterol was decreased (5%), and HDL:LDL was increased (12%) by the high-calcium diet compared with the low calcium diet.
The researchers concluded that “dairy calcium seems to partly counteract the raising effect of dairy fat on total and LDL cholesterol, without reducing HDL cholesterol.”
參考譯文：
《British Journal of Nutrition》期刊發表的一項研究表明，乳制品中存在的營養組合——鈣和乳脂，可能在降低脂肪吸收方面起著關鍵性作用，并具備將有害膽固醇（LDL）的升高降至最小程度的同時維持有益膽固醇（HDL）水平的能力。旨在探索為何含有飽和脂肪及高水平鈣的乳制品不會像其他含有飽和脂肪的食品那樣顯著的影響血液膽固醇水平的本次研究給這樣一種觀念——鈣含量很高的牛奶及其他乳制品如奶酪能有效降低心血管疾病風險提供了憑證依據。
作者指出，根據以往觀點，干預性研究已經證明了高水平飽和脂肪的膳食跟總膽固醇和LDL膽固醇值升高之間的聯系。也因此，一些營養專家建議消費者應控制高脂肪乳制品的攝入。然而，觀察性研究卻發現了牛奶及其他高鈣乳制品的攝入與心血管疾病發生率之間與上述觀點相左的關系。研究者想要驗證乳制品的高鈣含量是否影響乳品脂肪在血脂分析方面的效應。
該研究是一個包括9名參與者的小規模臨床試驗，他們于10天內完成4次獨立膳食——每一次的鈣含量和脂肪含量都不同。在每次進食前后分別測量其血液變量，并于進食結束后收集其糞便和尿液。應用雙因子變數分析（ANOVA）來檢驗鈣及脂肪的攝入效應。在不攝入鈣的條件下，相對于低脂肪膳食來說，高脂肪膳食增加了總膽固醇及LDL和HDL膽固醇值。然而，在不攝入脂肪的條件下，相對于低鈣膳食來說，高鈣膳食降低了總膽固醇及LDL膽固醇值并且不會降低HDL膽固醇的值。另外，相對于低鈣膳食來說，高鈣膳食的總膽固醇：HDL膽固醇值降低了5%，HDL:LDL值升高了12%。
研究者推斷“乳品中的鈣似乎能部分的抵消乳品中的脂肪對總膽固醇及LDL膽固醇值的影響，并且不會降低HDL膽固醇的值。”
期刊鏈接：British Journal of Nutrition
